Guangyi Zhang, Danxin Liang, Zisheng Zhao et al.

Environmental research • 2022

Tetracycline hydrochloride (TCH) is a typical antibiotic pollutant with high toxicity and persistence. The degradation of TCH and the generation of the associated electron mediator in a dual chamber microbial fuel cells (MFCs) were studied. The results of liquid chromatography revealed that TCH could be effectively removed (>93%) in MFCs mode. The maximum COD removal was 88.14 ± 1.47% in MFCs while it was 69.57 ± 1.36% in open circuit MFCs. According to cyclic voltammetry, the presence of the relevant redox peaks clearly suggested that the intermediates from TCH degradation could act as endogenous electron mediator. The highest power density of 120.02 ± 2.76 mW/m2 and the lowest internal resistance of 18.68 Ω were achieved in MFC with 2 mg/L of TCH. Microbial community analysis illustrated that Bacteroides, Comamonas, Clostridium_sensu_stricto, Desulfovibrio and Geobacter were enriched and played a dominant role in TCH degradation and power generation. Electrochemical active bacteria had certain tolerance to TCH and the inhibiting threshold value of TCH was below 5 mg/L. This study provided a new thinking that low concentration of TCH could produce electron mediators to improve the performance of MFC system.

Huang Jingyu, Nicholas Miwornunyuie, David Ewusi-Mensah et al.

Water science and technology : a journal of the International Association on Water Pollution Research • 2019

Constructed wetland coupled microbial fuel cell (CW-MFC) systems integrate an aerobic zone and an anaerobic zone to treat wastewater and to generate bioenergy. The concept evolves based on the principles of constructed wetlands and plant MFC (one form of photosynthetic MFC) technologies, of which all contain plants. CW-MFC have been used in a wide range of application since their introduction in 2012 for wastewater treatment and electricity generation. However, there are few reports on the individual components and their performance on CW-MFC efficiency. The performance and efficiency of this technology are significantly influenced by several factors such as the organic load and sewage composition, hydraulic retention time, cathode dissolved oxygen, electrode materials and wetland plants. This paper reviews the influence of the macrophyte (wetland plants) component, substrate material, microorganisms, electrode material and hydraulic retention time (HRT) on CW-MFC performance in wastewater treatment and electricity generation. The study assesses the relationship between these parameters and discusses progress in the development of this integrated system to date.

Minh Hang Do, Huu Hao Ngo, Wenshan Guo et al.

The Science of the total environment • 2021

This research explores the possibilities of a dual-chamber microbial fuel cell as a biosensor to measure Bisphenol A (BPA) in wastewater. BPA is an organic compound and is considered to be an endocrine disruptor, affecting exposed organisms, the environment, and human health. The performance of the microbial fuel cells (MFCs) was first controlled with specific operational conditions (pH, temperature, fuel feeding rate, and organic loading rate) to obtain the best accuracy of the sensor signal. After that, BPA concentrations varying from 50 to 1000 μg L-1 were examined under the biosensor's cell voltage generation. The outcome illustrates that MFC generates the most power under the best possible conditions of neutral pH, 300 mg L-1 of COD, R 1000 Ω, and ambient temperature. In general, adding BPA improved the biosensor's cell voltage generation. A slight linear trend between voltage output generation and BPA concentration was observed with R2 0.96, which indicated that BPA in this particular concentration range did not real harm to the MFC's electrogenic bacteria. Scanning electron microscope (SEM) images revealed a better cover biofilm after BPA injection on the surface electrode compared to it without BPA. These results confirmed that electroactive biofilm-based MFCs can serve to detect BPA found in wastewaters.

Ruggero Rossi, Bruce E Logan

Water research • 2022

Different microbial fuel cell (MFC) configurations have been successfully operated at pilot-scale levels (>100 L) to demonstrate electricity generation while accomplishing domestic or industrial wastewater treatment. Two cathode configurations have been primarily used based on either oxygen transfer by aeration of a liquid catholyte or direct oxygen transfer using air-cathodes. Analysis of several pilot-scale MFCs showed that air-cathode MFCs outperformed liquid catholyte reactors based on power density, producing 233% larger area-normalized power densities and 181% higher volumetric power densities. Reactors with higher electrode packing densities improved performance by enabling larger power production while minimizing the reactor footprint. Despite producing more power than the liquid catholyte MFCs, and reducing energy consumption for catholyte aeration, pilot MFCs based on air-cathode configuration failed to produce effluents with chemical oxygen demand (COD) levels low enough to meet typical threshold for discharge. Therefore, additional treatment would be required to further reduce the organic matter in the effluent to levels suitable for discharge. Scaling up MFCs must incorporate designs that can minimize electrode and solution resistances to maximize power and enable efficient wastewater treatment.

Dexter Hoi Long Leung, Yin Sze Lim, Kasimayan Uma et al.

Applied biochemistry and biotechnology • 2020

Microbial fuel cell (MFC) is a promising technology that utilizes exoelectrogens cultivated in the form of biofilm to generate power from various types of sources supplied. A metal-reducing pathway is utilized by these organisms to transfer electrons obtained from the metabolism of substrate from anaerobic respiration extracellularly. A widely established model organism that is capable of extracellular electron transfer (EET) is Shewanella oneidensis. This review highlights the strategies used in the transformation of S. oneidensis and the recent development of MFC in terms of intervention through genetic modifications. S. oneidensis was genetically engineered for several aims including the study on the underlying mechanisms of EET, and the enhancement of power generation and wastewater treating potential when used in an MFC. Through engineering S. oneidensis, genes responsible for EET are identified and strategies on enhancing the EET efficiency are studied. Overexpressing genes related to EET to enhance biofilm formation, mediator biosynthesis, and respiration appears as one of the common approaches.

Hong Liu, Bruce E. Logan

Environmental Science & Technology • 2004

Demonstration that removing the PEM in single-chamber MFCs can increase power generation.

Doaa Khodary Zater, Fatma I. Elzamik, Howaida M. Abdel Basit et al.

Sustainable Environment Research • 2024

Abstract This work evaluated the electrochemical, physical, biochemical, and molecular characterization of electrogens from a graphite felt anode when zinc oxide on activated carbon (ZnO/AC) was used as a cathodic electrocatalyst in a double-chambered microbial fuel cell (DCMFC). The electrochemical polarization behavior of the DCMFC showed that ZnO/AC had a higher power density (PD max ) of 89 mW m −2 with a corresponding cell current density (CD) of 248 mA m −2 and a voltage output of 395 mV, which was higher than those of the blank electrode used as a benchmark (PD max of 68 mW m −2 at a CD of 161 mA m −2 and a voltage of 421 mV). Furthermore, scanning electron microscopy and transmission electron microscopy revealed that the morphology and interior properties of the strains varied among the rods (bacilli), spirals (vibrios), and spheres (diplococci, staphylococci and streptococci). In addition, biochemical characterization via the Vitek2 compact system and molecular analysis via 16 S rRNA and 18 S rRNA gene sequencing revealed the occurrence of nine prevalent species that were correlated with Sphingobacterium spiritivorum, Ochrobactrum anthropicus, Pseudomonas mendocina, Stenotrophomonas maltophilia, Leuconostoc mesenteroides, Staphylococcus equorum, Bacillus subtilis HQ334981.1, Kocuria kristinae KC581674.1 and Saccharomyces cerevisiae NR111007.1. Consequently, the present study outlines different characterization strategies for electrogenic microbes that play an important role in the overall performance of DCMFC for scaling up and managing existing environmental pollution for sustainable energy generation.

Miroslav Hala, Roman Kodým, Martin Prokop et al.

ECS Meeting Abstracts • 2023

PEM fuel cells are a crucial link in the hydrogen economy because of their ability to transform the chemical energy of hydrogen into electrical energy with high efficiency at relatively low temperatures. Bipolar plates (BPs) are multifunctional components of PEM fuel cell stacks. Currently, material research in this field is focused on two promising material types: polymer carbon composites and metallic plates. Metallic plates have a number of advantages over composite materials, namely higher electrical conductivity, lower weight, and more effective manufacturing process. Typically, metallic BPs are manufactured with stamping or hydroforming. These methods are faster and cost-effective compared to machine milling or pressure extrusion typical for composite materials. Due to the nature of these processes, however, new channel geometries need to be considered. The first set of shape constrains comes from the forming properties of the material used. Other limitations result from the channel's ability to distribute the reagent gases, as well as to remove dissipate heat and water evolved. Traditional experimental testing methods involve an expensive and time-consuming production of samples and are unable to reliably determine local quantities. Within this study, mathematical modelling was used as a fast and cost-effective way of exploring the influence of the shape of the flow field channels on the distribution of local current density and species concentrations and performance of the PEM fuel cell. A full 3D model accounting for the reactants flow dynamics, multicomponent mass transport, electric charge flow, and electrode reaction kinetics was proposed and implemented. The Butler-Volmer equation was used to model the reaction kinetics. A simpler 1D model was developed to obtain the necessary kinetic parameters through fitting experimental data. Stefan-Maxwell equations were used to simulate the multicomponent mass transport on the cathode side of the cell. The data required were collected from the literature [1]. Darcy’s law was used to describe the transport of hydrogen in the porous structure of the anode. Through means of parametrical variation of geometrical parameters, such as the channel ground and rib width, angle of the channel walls, and the radius of the corners, we were able to compare numerous geometries in terms of the performance of the whole fuel cell. Also, the distribution of the species and local current densities was obtained. The width of the ribs and the ground of the channel were identified as the most influential parameters. In total, 18 combinations of channel ground and rib widths ranging from 0.1 to 4 mm and from 0.5 to 4 mm, respectively, were studied and compared to channels with square cross-section. In terms of the homogeneity of the local current densities, the narrowest combination offered the best results. This can be explained by the concentration of oxygen in the cathodic catalytic layer. In the case of wider channels, slow diffusion halted the transport of oxygen into the area of the catalytic layer at the closest distance from the channel ground, where the current was passing into the gas diffusion layer. This ultimately led to a large transport polarization and even fuel starvation in this area. Furthermore, in the well-supplied areas of the catalytic layer under the channels, where the bulk of gas transport is happening, local current densities were also low, because it is disadvantageous configuration for the electric charge flow. These two effects lead to a notably inhomogeneous local current density distribution with the most active area at the edge of the channel ground. In case of the narrow channels, it was possible to supply both reactants and charge into a larger area of the fuel cell, leading to much better utilization of the catalytical layer. From the obtained results, qualitative intervals of the ideal channel geometry were proposed. The results obtained contribute to the efficient development and faster commercialization of novel BPs. The CORE project Nr. TO01000306 benefits from Norway and Technology Agency of the Czech Republic Grant within the KAPPA Programme. [1] Bird, R. B.; Stewart, W. E.; Lightfoot, E. N. Transport Phenomena , 2nd ed.; John Wiley & Sons, Inc.: USA, 2006.

Tetsuya Nakamura, Kaito Mori, Shogo Fukushima et al.

ECS Meeting Abstracts • 2024

Boosting polymer electrolyte fuel cell (PEFC) performance is required in transportation. PEFC performance depends on the electrode reaction activity related to proton conductivity and oxygen diffusivity in catalyst layer (CL), consisting of Pt nanoparticles (Pt NPs), ionomer, water, and carbon supports. To achieve high proton conductivity and oxygen diffusivity, the optimization of CL structures such as Pt composition, ionomer/water distribution, and carbon support structures is essential by computational approaches, such as first-principles molecular dynamics (MD) and classical MD methods. The first-principles MD can describe chemical reactions, however can only simulate a small part of CL structures, consisting of a few hundred atoms. In contrast, classical MD can perform over 1 million atoms simulation to calculate whole CL structures, while the simple inter-atomic potential which enables 1 million atoms calculation, can not describe chemical reactions. Then, developing our original MD simulator "Laich", implementing MPI and OpenMP with ReaxFF inter-atomic potential, enabled us to calculate million atoms system reproducing whole CL structures and to simulate chemical reactions in whole CL structures. In this work, to design the higher-performance CL, we performed reactive MD simulations using a 1 million atoms CL model. A CL structure model was constructed with ionomers, water, Pt NPs, and carbon support. The carbon support composed of six meso pores with a size of 6 nm was constructed. To improve the hydrophilicity, hydroxyl groups and hydrogen terminated 32% and 31% of its surface carbon, respectively. Pt NPs were put on the carbon support at the exterior and in the interior of the meso pores. The Pt-supported carbon was coated with ionomers and water. Protons and oxygen were introduced into the system. Hereafter, we refer to this structure as a catalyst particle (CP) model (Fig. 1). To assess the influence of the carbon support structures on the electrode reactions, the oxygen diffusivity was evaluated from the trajectories of oxygen at the exterior and in the interior of the meso pores. Ideally, oxygen should be supplied to the Pt NPs without hindering its diffusion by obstacles. At the exterior of the meso pore, oxygen could not approach the Pt NPs, because ionomers and water were obstacles to the oxygen diffusion (Figs. 2(a)). Conversely, in the interior of the meso pores, oxygen could approach the Pt NPs via the gas phase since ionomers and water did not inhibit oxygen diffusion (Figs. 2(b)). From this analysis, the oxygen diffusivity showed higher value in the interior of the meso pores than at the exterior of the meso pores. Furtherly, it is reported that oxygen diffusivity in ionomers varies with temperature [1]. However, the influence of temperatures on oxygen diffusivity at the exterior and in the interior of the meso pores has not been analyzed. In this study, we calculated the mean squared displacement (MSD) and diffusion coefficients at 300 K and 365 K. At 300 K, oxygen diffusion coefficients (the linear regressions of MSD) at the exterior ( D exterior ) and in the interior of the meso pores ( D interior ) were 1.67×10 -10 m 2 /s and 3.02×10 -6 m 2 /s, respectively (Fig. 3(a)). At 365 K, D exterior and D interior were 12.3×10 -10 m 2 /s and 2.59×10 -6 m 2 /s, respectively (Fig. 3(b)). Therefore, D exterior and D interior respectively increased 7.37 and 0.86 times with increasing temperature. Next, to investigate whether the change of D exterior was caused only by temperatures, we calculated the oxygen diffusion coefficient at 1 atm ( D 1atm ) in an environment consisting of oxygen atoms only. As a result, D 1atm increased 1.05 times from 300 K to 365 K. By rising temperature, the increase of the oxygen diffusion coefficient showed 1.05 time at D 1atm , while it showed 7.37 time at D exterior . Therefore, other factors besides temperature affect the oxygen diffusivity. To identify the factors contributing to D exterior , we focused on the size of the water cluster, one of the obstacles to oxygen diffusion. Water clusters are defined as groups of water with an inter-molecular distance of less than 3.5 Å. The cluster size is defined as the number of water molecules forming the water cluster. Fig. 4 depicts the sizes of the 10 largest water clusters. As the temperature rose, the size of the largest water cluster decreased, while the size of other water clusters increased. These analyses indicate that the morphology of water clusters changed from continuous to discontinuous clusters with increasing temperature. Therefore, as water cluster sizes decrease by increasing temperature, oxygen diffuses through the gas phase. These results indicate that the control of the water cluster size improves the oxygen diffusivity. [1] K. Kudo et. al., Electrochim. Acta , 209 , 682-690 (2016). Figure 1

Miguel Mauricio Aguilera Flores, Verónica Avila Vázquez, Nahum Andrés Medellín Castillo

Frontiers in Sustainability • 2022

This work aimed to evaluate the devilfish bone char as an alternative material to be used as a bioanode in a microbial fuel cell (MFC) applied in bioenergy production from the pantoprazole biodegradation. The devilfish is an invasive species in Mexico and other countries, so its control and eradication are based on the integral use of its biomass. In addition, the bones are unusable waste and could be used as a raw material to manufacture the bioanode. Two MFCs with an anaerobic anode single chamber of 125 mL were operated independently using the fabricated bioanode and the carbon felt (conventional anode). Both MFCs were fed with 1 g/L of pantoprazole as substrate with a chemical oxygen demand (COD) of 210 ± 1.3 mg/L and 1.2 g of soil as inoculum. The two MFCs were characterized electrochemically, and the COD removal percentage was measured as an indicator of the pantoprazole biodegradation. The results showed that the MFC operated with the bioanode had a better performance than the conventional anode, since it reached a maximum power density of 1.22 mW/m 2 , being 156% higher than carbon felt. These values were consistent with the COD removal percentages reached in 10 days with values of 47.17 ± 0.23 and 43.34 ± 0.41%, respectively. Therefore, these findings provide a low-cost alternative carbonaceous material for the sustainable construction of MFC applied to produce bioenergy from the biodegradation of pharmaceutical products.

Ziqi Sun, Emiliana Fabbri, Lei Bi et al.

Journal of the American Ceramic Society • 2011

Although BaZr 0.8 Y 0.2 O 3−δ ( BZY ) possesses large bulk proton conductivity and excellent chemical stability, its poor sinterability and grain boundaries block proton conduction. In this work, the effect of Ca as a co‐dopant and as a sintering aid (as CaO ), on the sinterability, proton conductivity, and fuel cell performance of BZY was investigated. The addition of 4 mol% CaO significantly improved the BZY sinterability: BZY pellets with densities of 92.7% and 97.5% with respect to the theoretical density were obtained after sintering at 1500°C and 1600°C, respectively. The improved BZY sinterability by CaO addition resulted also in a large proton conductivity; at 600°C, the total conductivity of BZY– CaO was 2.14 × 10 −3 S/cm, in wet Ar . Anode‐supported fuel cells with 25 μm‐thick BZY– CaO electrolyte membranes were fabricated by a dual‐layer co‐firing technique. The peak power density of the fuel cell with a BZY– Ni /BZY–4 CaO /BZY–LSCF ( La 0.6 Sr 0.4 Fe 0.8 Co 0.2 O 3−δ ) configuration was 141 mW/cm 2 at 700°C, several times larger than the reported values of BZY electrolyte membrane fuel cells sintered with the addition of CuO or ZnO , demonstrating promising features for practical fuel cell applications.

V. Bandlamudi, P. Bujlo, V. Linkov et al.

Fuel Cells • 2019

Abstract Degradation of phosphoric acid doped polybenzimidazole membrane based fuel cells under accelerated potential cycling conditions is investigated in current study. Three unit cells with identical high temperature membrane electrode assembly were assembled with three different cathode flow field designs. The fuel cell is cycled between 0.5 V and 0.9 V with 3 min dwelling time for each voltage set point. Performance degradation mechanisms associated with differences in cathode flow design are identified. The fuel cell with multiple serpentine design is operated for a maximum of 4,821 potential cycles with only 38.6% of initial performance remaining at the end‐of‐test (EoT), whereas straight and parallel design operated for only 3,188 cycles. The electrochemical characterization studies reveal the cause of observed performance losses from polarization curves. Irrespective of the design type used there are very high activation losses observed which accelerated with accelerated stress tests (AST) testing. The impedance studies reveal high charge transfer resistance related to increased platinum crystal growth on cathode and reduced electrochemical surface area (ECSA) of catalyst. Overall the AST results in irreversible performance loss and severe degradation of the cathode catalyst support and catalyst itself.

Ilias Apostolopoulos, Georgios Bampos, Amaia Soto Beobide et al.

Energies • 2021

The aim of the study was to assess the effect of anode materials, namely a carbon nanotube (CNT)-buckypaper and a commercial carbon paper (CP) on the performance of a two-chamber microbial electrolysis cell (MEC), in terms of hydrogen production and main electrochemical characteristics. The experiments were performed using both acetate-based synthetic wastewater and real wastewater, specifically the effluent of a dark fermentative hydrogenogenic reactor (fermentation effluent), using cheese whey (CW) as substrate. The results showed that CP led to higher hydrogen production efficiency and current density compared to the CNT-buckypaper anode, which was attributed to the better colonization of the CP electrode with electroactive microorganisms, due to the negative effects of CNT-based materials on the bacteria metabolism. By using the fermentation effluent as substrate, a two-stage process is developed, where dark fermentation (DF) of CW for hydrogen production occurs in the first step, while the DF effluent is used as substrate in the MEC, in the second step, to further increase hydrogen production. By coupling DF-MEC, a dual environmental benefit is provided, combining sustainable bioenergy generation together with wastewater treatment, a fact that is also reinforced by the toxicity data of the current study.

Zhe Lv, Xiaoying Huang, Xin Liu

ECS Transactions • 2021

In this work, button single cells with Ni-YSZ (anode support) | YSZ (electrolyte membrane) | Gd 0.1 Ce 0.9 O 1.95 (barrier layer) | La 0.6 Sr 0.4 Co 0.2 Fe 0.8 O 3-δ (cathode) structure produced by mass-producing under industrial conditions were operated with dry hydrogen as fuel. In order to simulate single cell unit failure in series stack and local region failure of one cell, fuel gas depletion experiments were carried out in constant current and constant voltage discharge modes, respectively. During the discharging processes, the hydrogen fuel was fed and cut off alternatively for several times with different cut-off time, the output performances were measured to evaluate the stability and healthy of the single cell. The results show that the long time fuel depletion of the cell discharging in constant current mode can directly destroy the cell, it means a cell unit’s life in series stack can be affected when suffered fuel depletion. However, the cell discharging in constant voltage mode can keep stable status under fuel depletion condition, it means that the local fuel depletion in a certain cell will not destroy it.

Denver F. Cheddie, Norman D. H. Munroe

ASME 2006 Fourth International Conference on Fuel Cell Science, Engineering and Technology, Parts A and B • 2005

A parametric model of a proton exchange membrane fuel cell (PEMFC) operating with a polybenzimidazole (PBI) membrane is presented. The model is three dimensional and applicable for PEMFCs operating at intermediate temperatures (120–150 °C). It accounts for all transport and polarization phenomena, and the results compare well with published experimental data for equivalent operating conditions. Results for oxygen concentration and temperature variations are presented. The model predicts the oxygen depletion, which occurs in the catalyst area under the ribs, and which gives an indication of the catalyst utilization. Results also predict that for an output power density of 1 kW m−2, a cell temperature rise of up to 30 K can be expected for typical laboratory operating conditions. Parametric analyses indicate that significant gain in fuel cell performance can be expected by increasing the conductivity of the PBI membrane. Further, results demonstrate that when the catalyst region is well utilized, increasing the catalyst activity results in only a small improvement in performance.

Zhaodong Li, Chao Wu, Xiang Gao et al.

Research Square (Research Square) • 2020

Abstract Nature’s biocatalytic processes are driven by photosynthesis, whereby photosystems I and II are connected in series for light-stimulated generation of fuel products or electricity. Externally supplying electricity directly to the photosynthetic electron transfer chain (PETC) has numerous potential benefits, although strategies for achieving this goal have remained elusive. Here we report an integrated photo-electrochemical architecture which shuttles electrons directly to PETC in living cyanobacteria. The cathode of this architecture electrochemically interfaces with cyanobacterial cells lacking photosystem II activity that cannot perform photosynthesis independently. Illumination of the cathode channels electrons from external circuit to intracellular PETC through photosystem I, ultimately fueling CO2 conversion to acetate, a model fuel molecule with 9.32% energy efficiency, exceeding the efficiency of natural photosynthesis in higher plants (<1%) and cyanobacteria (~4-7%). The resulting “Electrophototrophic” bio-electrochemical hybrid has the potential to produce fuel chemicals with numerous advantages over standalone natural and artificial photosynthetic approaches.

Mehmet Suha Yazici, Tahsin Bahar

Asia-Pacific Journal of Chemical Engineering • 2021

Abstract Different cathode configurations with carbon paper (CP) and carbon cloth (CC) gas diffusion layer (GDL) are combined with Nafion® 115 for GOx enzyme fuel cells. Catalyst‐coated Nafion membrane (without a GDL) has resulted with highest impedance and lowest polarization response. Hot pressing of cathode gas diffusion electrode (GDE) onto the Nafion or physical placement onto the alternative chitosan membrane has reduced interface resistance 10 times compared with no‐GDL case. The best performance for the Nafion membrane is 2.1 mA cm −2 current density with hot‐pressed CC‐GDE. Smallest high‐frequency electrolyte (0.55 ohm) and charge transfer resistances (0.15 ohm) were measured with physically placed CC‐GDE on the alternative chitosan membrane resulting in maximum short current density of 3 mA cm −2 with a 4‐cm 2 single enzyme fuel cell.

Seung Woo Lee, Chae kyung Baik, Yong-Hun Cho et al.

ECS Meeting Abstracts • 2019

In the recent five years, the performance of alkaline membrane fuel cells (AMFCs) is greatly enhanced along with the development of alkaline electrolyte membrane and electrode technology including the ionomers and PtRu catalyst [1-3]. By replacing the Pt/C catalyst in the anode to PtRu/C catalyst, the performance of membrane electrode assembly (MEA) is improved significantly, which attributed to the lowering of hydrogen binding energy by PtRu alloy [3,4]. On the contrary, the adoption of non-platinum group metal (PGM) catalysts for hydrogen oxidation reaction (HOR) in the anode showed the very poor performance until now in the MEA level due to the very low HOR activity [1,5]. Thus, the further investigation of HOR catalysts with PGM having high activity and durability under alkaline condition is demanded. Among the PGM, recently, Ir and Ru have been received increasing attention as an alternative for the Pt catalyst for HOR because of their comparable exchange current density to that of Pt [1]. Recently, alloying of Ir and Ru provide the enhancement of HOR activity under alkaline condition in the half-cell evaluation [6,7]. In addition, Ir 1 Ru 1 nanowire supported on carbon catalyst displayed the higher performance as an anode catalyst than that of Pt/C catalyst in the MEA level [8]. In this study, the effect of metal loading of Ir 1 Ru 4 alloy supported on carbon support on the MEA performance is investigated. The metal loading of Ir 1 Ru 4 alloy is increased to 60 wt.% by repeating twice the impregnation and reduction processes for 30 wt.% loading, which applied to mitigate the enlargement of IrRu alloy nanoparticle when the metal loading increase from 30 wt.% to 60 wt.%. The MEA performance of 30 wt.% and 60 wt.% Ir 1 Ru 4 /C catalyst as a HOR catalyst is investigated by making the anode (0.4mg/cm 2 ) using a spray fabrication method. The current density at 0.6V is increased from the 0.6 to 0.93 A/cm 2 by increasing the metal loading in the supported Ir 1 Ru 4 alloy catalysts, which indicates the thickness of electrode is one factor for enhancing the MEA performance. In addition, the optimum ionomer to catalyst ratio is obtained as 0.3 for the 60 wt.% Ir 1 Ru 4 /C catalyst, which showed slightly better MEA performance than that of 40 wt.% Pt. This work was also supported by the Technology Development Program to Solve Climate Changes of the National Research Foundation (NRF) funded by the Ministry of Science and ICT (Grant NRF-2018M1A2A2063172 and NRF-2018M1A2A2063174). References E. S. Davydova, S. Mukerjee, F. Jaouen, and D. R. Dekel, ACS Catal. 8 , 6665 (2018) D. R. Dekel, J. Power Sources , 375 , 158 (2018). Y. Wang, G. Wang, G. Li, B. Huang, J. Pan, Q. Liu, J. Han, L. Xiao, J. Lu, and L. Zhuang, Energy Environ. Sci. , 8 , 177 (2015). W. Sheng, M. Myint, J. G. Chen and Y. Yan, Energy Environ. Sci., 6 , 1509 (2013). S. M. Alia and B. S. Pivovar, J. Electrochem. Soc. , 165 , F441 (2018). H. Wang and H. D. Abruna, J. Am. Chem. Soc. , 139 , 6807 (2017). J. Ohyama, D. Kumba abd A. Satsuma, J. Mater. Chem. A, 4 , 15980 (2016).

Jianuo Chen, Xuekun Lu, Lingtao Wang et al.

Nature Communications • 2024

Abstract High-temperature proton exchange membrane fuel cells (HT-PEMFCs) offer solutions to challenges intrinsic to low-temperature PEMFCs, such as complex water management, fuel inflexibility, and thermal integration. However, they are hindered by phosphoric acid (PA) leaching and catalyst migration, which destabilize the critical three-phase interface within the membrane electrode assembly (MEA). This study presents an innovative approach to enhance HT-PEMFC performance through membrane modification using picosecond laser scribing, which optimises the three-phase interface by forming a graphene-like structure that mitigates PA leaching. Our results demonstrate that laser-induced modification of PA-doped membranes, particularly on the cathode side, significantly enhances the performance and durability of HT-PEMFCs, achieving a peak power density of 817.2 mW cm⁻² after accelerated stress testing, representing a notable 58.2% increase compared to untreated membranes. Furthermore, a comprehensive three-dimensional multi-physics model, based on X-ray micro-computed tomography data, was employed to visualise and quantify the impact of this laser treatment on the dynamic electrochemical processes within the MEA. Hence, this work provides both a scalable methodology to stabilise an important future membrane technology, and a clear mechanistic understanding of how this targeted laser modification acts to optimise the three-phase interface of HT-PEMFCs, which can have impact across a wide array of applications.

K Scott, I Cotlarciuc, I Head et al.

Journal of Chemical Technology & Biotechnology • 2008

Abstract BACKGROUND: Marine sediment microbial fuel cells (MFC) utilise oxidisable carbon compounds and other components present in sediments on ocean floors and similar environments to produce power in conjunction with, principally, oxygen reduction at the cathode in the overlying water. The aim of the work was to investigate a range of cathode materials for sediment MFC, to achieve relatively high levels of power. RESULTS: Cell potential and power density performance data are reported for sediment MFC using cathodes of: carbon sponge, cloth and paper, graphite and reticulated vitreous carbon (RVC), Co and Fe‐Co tetramethoxyphenyl porphyrin (FeCoTMPP) and platinised carbon and titanium. The anode was graphite cloth. After a period of stabilisation, open circuit voltages of 700 mV and maximum power densities of 62 mW m −2 were obtained, using FeCoTMPP. Relatively low cost carbon cathodes gave power densities of around 30 mW m −2 . CONCLUSIONS: The study has shown that low level power can be produced from marine sediments using MFC without separators between the fuel and seawater containing dissolved oxygen. Cathode performance was an important factor determining the power output. Electrocatalyst at the cathode improved performance: FeCoTMMP gave power densities of 60 mW m −2 which was twice that achieved with the best un‐modified carbon. Copyright © 2008 Society of Chemical Industry

Xinhai Xu, Shuyang Zhang, Peiwen Li

ASME 2014 12th International Conference on Fuel Cell Science, Engineering and Technology • 2014

Catalytic autothermal reforming (ATR) is one promising technology to effectively produce hydrogen and syngas from heavy hydrocarbon fuels for fuel cell applications. The present study describes the development of a cylindrical 1.5 kWe scale autothermal reformer for on-board SOFCs. NiO-Rh bimetallic catalysts supported on 400 cpsi cordierite monoliths were experimentally examined in the reformer. Promoters including cerium, potassium and lanthanum were introduced in the catalysts preparation to improve their performance. Dodecane (C12H26) was used as a surrogate for desulfurized commercial Jet-A fuel (C11.6H22.3) to study the hydrogen selectivity and efficiency of ATR reactions with different catalysts. Gas chromatography (GC) equipped with TCD detector was used to monitor the concentration of H2, CO, CO2 and N2 in the reformate. The catalysts screening tests were performed at the same operation conditions including inlet temperatures, reactor temperature, steam to carbon ratio and oxygen to carbon ratio. The best catalyst was reported to have efficiency about 85 percent. The optimized reactor operation temperature was reported as 700 °C.

Carlos Munoz‐Cupa, Amarjeet Bassi

Environmental Progress & Sustainable Energy • 2023

Abstract Heavy metal removal and simultaneous energy production were studied using a dual chambered Microbial Fuel Cell inoculated with Shewanella oneidensis MR‐1 in the anode. Synthetic wastewater was prepared with Cu (II), Mg (II), Mn (II), Zn (II), Na, and Phenol based on desalter effluent from refinery processes at different metal concentrations. In this study, a maximum open‐circuit voltage of 517.6 mV was reached at Conc. 5 with wastewater in the anode chamber, and 127.7 mV at Conc. 3 was produced with synthetic wastewater in the cathode chamber. Moreover, μ at Conc. 5 was 0.1133 h −1 , demonstrating bacterial growth under metal and phenol concentrations. The highest metal removal in the anode for Cu (II), Mg (II), Mn (II), Zn (II), and Na was 93%, 85%, 93%, 88%, and 36%, respectively. In the cathode chamber the removal of Cu (II), Mg (II), Mn (II), Zn (II), and Na was 98%, 49%, 57%, 59%, and 36%, respectively. During the operation in the anode, SEM images showed that the bacterial nanowires are formed in response to toxic and anaerobic environments which contribute to the bacterial growth. These nanowires increased the metal removal and the voltage production as a consequence of a higher electron rate from the anode to the cathode due to the higher extracellular membrane surface area. S. oneidensis is a bacterium with metal‐reducing characteristics, and it is suitable for metal removal and electron transport from carbon sources, demonstrated in voltage production with microbial fuel cells.

Li-Chun Wu, Guey-Horng Wang, Teh-Hua Tsai et al.

Sensors • 2019

Chromium (VI) [Cr(VI)] compounds display high toxic, mutagenic, and carcinogenic potential. Biological analysis techniques (e.g., such as enzyme-based or cell-based sensors) have been developed to measure Cr(VI); however, these biological elements are sensitive to the environment, limited to measuring trace Cr(VI), and require deployment offsite. In this study, a three-stage single-chambered microbial fuel cell (SCMFC) biosensor inoculated with Exiguobacterium aestuarii YC211 was developed for in situ, real-time, and continuous Cr(VI) measurement. A negative linear relationship was observed between the Cr(VI) concentration (5–30 mg/L) and the voltage output using an SCMFC at 2-min liquid retention time. The theoretical Cr(VI) measurement range of the system could be extended to 5–90 mg/L by connecting three separate SCMFCs in series. The three-stage SCMFC biosensor could accurately measure Cr(VI) concentrations in actual tannery wastewater with low deviations (<7%). After treating the wastewater with the SCMFC, the original inoculated E. aestuarii remained dominant (>92.5%), according to the next-generation sequencing analysis. The stable bacterial community present in the SCMFC favored the reliable performance of the SCMFC biosensor. Thus, the three-stage SCMFC biosensor has potential as an early warning device with wide dynamic range for in situ, real-time, and continuous Cr(VI) measurement of tannery wastewater.

Nour-eddine Lazar, Driss Mazkad, Hamza Kharti et al.

Materials for Renewable and Sustainable Energy • 2024

Abstract Microbial fuel cells (MFCs) have attracted a great deal of attention as a promising technology for recovering electricity from organic substances by harnessing the metabolic activities of microorganisms. The objective of this study is to assess the efficacy of a LiTa 0.5 Nb 0.5 O 3 /g-C 3 N 4 (LTN/g-C 3 N 4 ) heterojunction as a photocathode catalyst within a single-chamber microbial fuel cell operating under both light irradiation and dark conditions. X-Ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and Energy dispersive X-Ray spectroscopy (EDS) were used to conduct a comprehensive analysis of the composite catalyst, revealing its exceptional purity and unique properties. After 120 h of exposure to visible light, the maximal power density of the MFC containing LTN/g-C3N4-modified carbon cloth was determined to be 667.7 mW/m 3 . The power density achieved with the presence of light was approximately three times greater than the power density obtained without light in the MFC (235.64 mW/m 3 ). In addition, the study determined that the removal efficiencies of chemical oxygen demand (COD) were 88.4% and 66.5% when exposed to light and in the absence of light, respectively. These findings highlight the potential of the non-precious LTN/g-C 3 N 4 photocatalyst as a viable alternative for effective wastewater treatment and power generation in microbial fuel cells with a single chamber configuration.

Farzad Ahmadi, Ramin Roshandel

Journal of Fuel Cell Science and Technology • 2013

Performance of polymer electrolyte membrane fuel cells (PEMFC) at high current densities is limited to transport reactants and products. Furthermore, large amounts of water are generated and may be condensed due to the low temperature of the PEMFC. Development of a two-phase flow model is necessary in order to predict water flooding and its effects on the PEMFC performance. In this paper, a multiphase mixture model (M2) is used, accurately, to model two-phase transport in porous media of a PEMFC. The cathode side, which includes channel, gas diffusion layer (GDL), microporous layer (MPL), and catalyst layer (CL), is considered as the computational domain. A multidomain approach has been used and transport equations are solved in each domain independently with appropriate boundary conditions between GDL and MPL. Distributions of species concentration, temperature, and velocity field are obtained, and the effects of MPL on species distribution and fuel cell performance are investigated. MPL causes a saturation jump and a discontinuity in oxygen concentration at the GDL/MPL interface. The effect of MPL thickness on fuel cell performance is also studied. The results revealed that the MPL can highly increase the maximum power of a PEMFC.

Nie Luo, George H. Miley, Joe Mather et al.

ASME 2006 Fourth International Conference on Fuel Cell Science, Engineering and Technology, Parts A and B • 2005

A kilo-Watt-class direct sodium-borohydride/hydrogen-peroxide (NaBH4/H2O2) fuel cell is fabricated and characterized in this research. Aqueous solution of NaBH4 is directly utilized at the fuel cell anode in place of gaseous hydrogen. Similarly H2O2/water solution is directly reduced at the cathode without being first converted through molecular oxygen. The direct utilization of fuel/oxidant results in much higher (35% higher) efficiency in energy utilization. The potential for a very high efficiency (over 80%) was fully validated in the experiments, because the use of H2O2 overcomes the oxygen over-potential problem inherent to prior H2/O2 fuel cell designs. Initial results indicate: 1) conversion efficiency over 50% at a practical current density of 200 mA/cm2; 2) power density over 0.5 W/cm2, at 60 degree Celsius. The kilo-Watt-stack consists of 24 cells, generating an OCV (open circuit voltage) of ∼ 42 V. The design of the reactant manifold overcomes some issues unique to an all-liquid-reactant fuel cell. Such a technology is ideal for propulsion/power in air independent environment such as space and underwater.

Karren L. More, David A. Cullen, Brian Sneed et al.

ECS Meeting Abstracts • 2016

Polymer electrolyte membrane (PEM) fuel cell performance and materials degradation, particularly associated with the cathode catalyst layer (CCL), can be directly attributed to the structure and chemistry of individual material components, as well as their uniformity/homogeneity within a CCL. The individual material constituents used to form the CCL within the membrane electrode assemblies (MEAs), which include the electrocatalyst, catalyst support, and ionomer films, and especially the critical interfaces that are formed between these various constituents, are critically importance in controlling fuel cell perfomance. Understanding the specific microstructural characteristics of the individual materials within the CCL, and how the materials interact to “form” the CCL, is important for identifying materials optimization parameters that can significantly enhance performance and durability. Materials in several states/conditions, e.g., prior to incorporation in the CCL (as-synthesized), after MEA preparation (CCL), and after fuel cell testing, are beig evaluated and quantified using a combination of advanced electron microscopy methods, which are used to interrogate the materials constituents and interfacial structures and chemistries from the μm- to the Å-level. The as-processed (prior to and following incorporation into a CCL) microstructural evidence is directly correlated with observations of materials-specific degradation mechanisms that contribute to fuel cell performance loss, and are then used to identify potential processing variables (materials-based mitigation strategies) to improve the microstructure and compositional homogeneity within the electrode structure, and enhance MEA durability and stability during fuel cell operation. Research efforts at Oak Ridge National Laboratory are focused on the high-resolution microstructural and microchemical characterization of MEAs fabricated using different electocatalysts (typically Pt-based) and catalyst loadings, carbon-based support materials, and ionomer solutions, as well as the same MEAs subjected to accelerated stress tests (ASTs) designed to degrade specific MEA components. While a significant microscopy effort has been aimed towards understanding catalyst degradation (e.g., coarsening, de-alloying), recently, high-resolution analytical microscopy methods have been used to directly image/map the distribution and chemistry of the ionomer films/layers within CCLs, results of which are being combined with high-resolution imaging and 3-D tomography data of powder materials and MEAs, to provide unprecedented insight into the MEA architecture and interfaces (ionomer/support, ionomer/catalyst, catalyst/support, ionomer/pore). This presentation will focus on understanding materials distributions within CCLs as a function of materials used and ink/MEA processing variables, e.g., initial ionomer and/or ink chemistry, electrocatalyst (type, content, and dispersion), and the type of carbon support used. Additionally, the stability of the ionomer films, electrocatalysts, and support structures in CCLs following ASTs designed specifically for either catalyst degradation or carbon corrosion, will be evaluated. ________________________________________________________________________ Research sponsored by (1) the Fuel Cell Technologies Office, Office of Energy Efficiency and Renewable Energy, U.S. Department of Energy and (2) Oak Ridge National Laboratory’s Center for Nanophase Materials Sciences (CNMS), which is a U.S. Department of Energy, Office of Science User Facility.

Bahareh Alsadat Tavakoli Mehrabadi, Jonathan Braaten, Gang Wu et al.

ECS Meeting Abstracts • 2020

One of the effective ways to reduce the cost of polymer electrolyte membrane fuel cells (PEMFCs) is to reduce the amount of platinum-group metal (PGM) catalysts used for the oxygen reduction reaction (ORR). Recently, highly active platinum group metal-free (PGM-free) catalysts were developed and applied for the ORR reaction [1-3]. Significant developments have been made on the chemistry of PGM-free catalysts and their kinetic performance [4-6]. However, despite all the progress, some challenges remain before they are commercially viable. Mass-transport within the very thick catalyst layer (CL) displays a key challenge for further improvement of the fuel cell performance of PGM-free catalysts. Understanding of the structure of CL including the distribution of active sites and the ionomer inside the CL play an important role in the development of stable PGM-free cathodes capable of high power density. In the present work, our objective has been to demonstrate the effects of the ionomer content, solvents, and equivalent weight (EW) on electrode performance. The structure of the ionomer (i.e., short-side-chain vs long-side chain ionomer) as well as the effect of the relative humidity (RH) have been considered. To increase the proton conductivity of the cathode and improve the catalysts’ effectiveness across its thickness, it is important to optimize the ionomer type and its EW. In this work, we used the nanoscale X-ray computed tomography (nano-CT) method to characterize the morphology and transport properties of PGM-free cathodes. Our results show the sensitivity of the cathode’s performance to the hydrophilicity of the ionomer films. We found that electrodes with a lower ionomer EW have a tendency to retain more water than electrodes with a higher EW. Thus, at high current density conditions where significant water is being generated, the lower EW ionomers showed reduced performances due to electrode flooding when using the same processing and ionomer loading. In general, higher MEA performance at 100% RH was achieved using more hydrophobic ionomers (higher EW) with a greater proportion of hydrophobic fluoropolymer backbone or by using ink formulations that enhanced the hydrophobicity of a particular ionomer. Acknowledgment This material is based upon work supported by the U.S. Department of Energy’s Office of Energy Efficiency and Renewable Energy (EERE) under the Fuel Cell Technologies Office (FCTO) under Award Number DE-EE0008076. References 1. F. Jaouen, E. Proietti, M. Lefevre, R. Chenitz, J. Dodelet, G. Wu, H. Chung, C. Johnston, P. Zelenay, Energ. Environ. Sci. 4, 114-130 (2011). 2. G. Wu, K.L. More, C.M. Johnston and P. Zelenay, Science. 332, 443-447 (2011). 3. J. Suntivich, K.J. May, H.A. Gasteiger, J.B. Goodenough and Y. Shao-Horn. Science. 334, 1383-1385 (2011). 4. G. Wu and P. Zelenay, Acc. Chem. Res. 46, 1878-1889 (2013). 5. E. Proietti, F. Jaouen, M. Lefèvre, N. Larouche, J. Tian, J. Herranz and J.-P. Dodelet, Nat. Commun. 2, 416 (2011). 6. X. Wang, H. Zhang, H. Lin, S. Gupta, C. Wang, Z. Tao, H. Fu, T. Wang, J. Zheng, G. Wu and X. Li, Nano Energy. 25, 110-119 (2016).

Natalia Macauley, Magali Spinetta, Sichen Zhong et al.

ECS Meeting Abstracts • 2020

In a proton exchange membrane (PEM) fuel cell, the local oxygen transport across the ionomer film in the catalyst layer has a significant impact on electrode performance especially at high current density. 1 It is therefore crucial to use ionomers that have higher oxygen permeability than the baseline Nafion. In this work, novel ionomers with increased oxygen permeability have been synthesized by copolymerization of perfluoro-2,2-dimethyl-1,3-dioxole (PDD) with perfluoro(4-methyl-3,6-dioxaoct-7-ene) sulfonyl fluoride (PFSVE) and a ter-monomer. PDD is the main source of higher permeability due to its bulky structure, PFSVE provides ionic conductivity and the amount of the ter-monomer is adjusted to achieve high yields without compromising the equivalent weight (EW). The ring structure of PDD creates additional open space within the ionomer structure for improved gas permeability. Some of the newly developed ionomers have up to five times higher permeability than Nafion, which should result in a significant improvement of fuel cell performance, mainly at high current densities. Ionomers with different PDD content and equivalent weight have been studied to establish the correlation between ionomer properties and MEA performance. Local oxygen resistance, ionomer sheet resistance, ionomer coverage, and SO 3 - group coverage will be evaluated and correlated to electrode performance. The performance and durability of the electrodes using high permeability ionomer will be correlated to the ionomer interaction with catalyst particle. This work will provide a comprehensive understanding of interactions among Pt, carbon, ionomer and their impact on the electrode structure and fuel cell performance and durability. The attained information will be used to improve fuel cell electrode design. Acknowledgement: The project is financially supported by the Department of Energy’s Fuel Cell Technology Office under the Grant DE-SC0018597. References: 1. Baker et al, J. Electrochem. Soc. 156, B991 (2014).

Mengfan Zhou, Steffen Frensch, Vincenzo Liso et al.

Energies • 2022

In this paper, the performance of a high-temperature polymer electrolyte membrane fuel cell (HT-PEMFC) was modeled using literature data. The paper attempted to combine different sources from the literature to find trends in the degradation mechanisms of HT-PEMFCs. The model focused on the activation and ohmic losses. The activation losses were defined as a function of both Pt agglomeration and loss of catalyst material. The simulations revealed that the loss of electrochemical active surface area (ECSA) was a major contributor to the total voltage loss. The ohmic losses were defined as a function of changes of acid doping level in time. The loss of conductivity increased significantly on a percentage basis over time, but its impact on the overall voltage degradation was fairly low. It was found that the evaporation of phosphoric acid caused the ohmic overpotential to increase, especially at temperatures above 180 °C. Therefore, higher temperatures can lead to shorter lifetimes but increase the average power output over the lifetime of the fuel cell owing to a higher performance at higher temperatures. The lifetime prognosis was also made at different operating temperatures. It was shown that while the fuel cell performance increased linearly with increasing temperature at the beginning of its life, the voltage decay rate increased exponentially with an increasing temperature. Based on an analysis of the voltage decay rate and lifetime prognosis, the operating temperature range between 160 °C and 170 °C could be said to be optimal, as there was a significant increase in performance compared to lower operating temperatures without too much penalty in terms of lifetime.

Sandhya Prakash, Samsudeen Naina Mohamed, Kalaichelvi Ponnusamy

Water and Environment Journal • 2024

Abstract This study aims to improve the performance of microbial desalination cell (MDC) using Vigna mungo (Black gram) wash water, reported for the first time as an anolyte utilizing a graphite plate and carbon brush as the anode. Power generation was facilitated by the exoelectrogen, Shewanella putrefaciens MTCC 8104. Polarization studies revealed that the graphite plate MDC attained a high power density of 2720 ± 50 μW/m 2 compared to carbon brush for two electrode pairs. The COD removal and desalination efficiency were better for carbon brush MDC, achieving 58.17 ± 2% and 38.14 ± 2% removal, respectively. Power production can be enhanced by increasing the cathode's ability to accept the electrons, reducing the ageing of biofilm and promoting complete oxidation of the substrates. Upon improving its performance, MDC can act as a sustainable technology, collaborating with industries seeking solutions for wastewater treatment, energy generation and agricultural sectors on a large scale.

Hongzhi Ma, Cheng Peng, Yan Jia et al.

Royal Society Open Science • 2018

A single-chamber microbial fuel cell (MFC) was used in this study to treat recycled stillage obtained from food waste ethanol fermentation. Corresponding substrates inside the system were evaluated by fluorescence spectra, and microbial communities were also investigated. Results demonstrated that output voltage and current, respectively, reached 0.29 V and 1.4 mA with an external resistance of 200 Ω. Corresponding total organic carbon and chemical oxygen demand removal efficiency reached more than 50% and 70%, respectively. Results of fluorescence spectra demonstrated that tryptophan-like aromatic, soluble microbial by-product-like and humic acid-like substances accumulated and were not easily degraded. Microbial community analysis by high-throughput sequence indicated that Advenella and Moheibacter occupied the highest proportion among all genera at the anode instead of Geobacter . These results may be due to complicated accumulated stillage, and potential tetracyclines possibly influenced microbial communities. Details on how stillage affects MFC operation should be further studied, and a solution on relieving effects should be established.

Anam Asghar, Addin Salihoudin, Abdul Aziz Abdul Raman et al.

Environmental Progress & Sustainable Energy • 2016

Microbial fuel cell (MFC) is a sustainable and energy efficient technology, which uses graphite as cathode for hydrogen peroxide (H 2 O 2 ) production often with simultaneous power production. Nevertheless, slow kinetics of oxygen reduction reaction (ORR) at the surface of graphite often results in poor performance of MFC. In an attempt to improve the performance of MFC for in‐situ H 2 O 2 production, a treatment of graphite cathode using nitric acid was performed. The treatment was conducted in three steps (i) heat treatment at 450°C for 2 h; (ii) acid treatment with concentrated nitric acid for 5 h; and (iii) drying at 120°C for 2 h. After the treatment, four times increase in surface area of treated cathode (GR‐HA) was observed. Energy‐dispersive X‐ray spectroscopy (EDX) and Fourier transform infrared (FTIR) analysis revealed the presence of nitrogen and quinone based functional groups on the surface of GR‐HA. Cyclic voltammetric (CV) analysis of GR‐HA cathode further confirmed the production of H 2 O 2 at the peak current value of −3.7 mA and on‐set potential of −0.1 V. Following CV analysis, H 2 O 2 production experiments were performed in a dual chamber MFC using GR‐HA as cathode. Maximum 150 mg/L of H 2 O 2 was produced with simultaneous power production of 36.438 mW/m 2 . Approximately, 25% increase in both H 2 O 2 and power production was observed in the case of G cathode. Subsequently, Fenton oxidation experiments were performed (with GR‐HA and GR‐CA cathodes) to determine the efficacy of in‐situ produced H 2 O 2 . This resulted in an increase of 8.28%, 11.04%, and 31.32% in decolorization, chemical oxygen demand (COD), and Total Organic Carbon (TOC) removal efficiency, respectively. © 2016 American Institute of Chemical Engineers Environ Prog, 36: 382–393, 2017

Partha P. Mukherjee, Chao-Yang Wang

ASME 2008 6th International Conference on Fuel Cell Science, Engineering and Technology • 2007

It is widely recognized that the performance degradation and the limiting current behavior in polymer electrolyte fuel cells (PEFC) are mainly attributed to the excessive build up of liquid water in the cathode side and the resulting flooding phenomena. Liquid water blocks the open pore space in the catalyst layer (CL) and the gas diffusion layer (GDL) leading to hindered oxygen transport and covers the electrochemically active sites in the CL thereby rendering reduced catalytic activity. The CL flooding therefore plays a crucial role in the overall PEFC performance limitation. In order to elucidate the primary mechanisms of liquid water removal out of the CL, the factors affecting CL flooding and to discern the role and contribution of CL flooding on the overall PEFC voltage loss, a CL flooding model has been developed. The flooding model is based on a simplified structure-wettability representation of the PEFC CL and a physical description of water and heat balance along with electrochemical performance analysis. The model shows that the evaporation mechanism, depending upon the cell operating temperature and the GDL thermal conductivity, plays a crucial role in the CL flooding behavior and the cell performance.

Aswini Vellingiri, Young Eun Song, Ganapathiraman Munussami et al.

Journal of Chemical Technology & Biotechnology • 2018

Abstract BACKGROUND The c‐type cytochrome of the CymA of Shewanella oneidensis MR‐1 is essential for the anaerobic respiration of Shewanella sp . and transfers electrons from the inner membrane to various terminal electron acceptors, such as soluble redox shuttles and insoluble metal oxides. CymA is believed to be a passage to the outer membrane for dissipating the respiratory electron to the carbon electrode in a microbial fuel cell (MFC) with simultaneous electricity generation. While the deletion and heterologous expression of cymA in Escherichia coli have been studied, there are no reports of the overexpression and its effects on the corresponding bioelectrochemical performance in a MFC. RESULTS The cymA gene was overexpressed in Shewanella oneidensis MR‐1, and its upregulation was examined under aerobic, anaerobic, and MFC operating conditions by a reverse transcription‐polymerase chain reaction (RT‐PCR). Overexpression of the CymA protein was confirmed by sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS‐PAGE). The MFCs inoculated with the engineered strains of MR‐1 achieved a higher maximum power of 0.13 mW and specific growth rate of 0.087 h −1 than those of the wild type MR‐1 (0.11 mW and 0.043 h −1 , respectively). The higher electrochemical activity of the mutant strains demonstrated by cyclic voltammetry and linear sweep voltammetry, indicates that more respiratory electrons can be transferred to the electrodes through overexpression of the cymA gene of MR‐1 in a MFC. CONCLUSION Overexpression of CymA improves the bioelectrochemical performance of MFCs. This suggests that metabolic engineering of a membrane‐associated redox protein, such as CymA, can further improve electricity generation of MFCs and produce an electrochemically enhanced bioprocess. © 2018 Society of Chemical Industry

Denis Bona, Dennis E. Curtin, Francesco Pedrazzo et al.

Journal of Fuel Cell Science and Technology • 2013

Carbon black based electrodes are generally recognized as state of the art for PEM fuel cell technology due to the high performance achieved with a relatively low Pt content. However, the catalyst carbon support is prone to carbon oxidation. This leads to a loss of the catalyst area and overall performance, along with a higher mass transport loss due to an increased flooding tendency. This phenomenon is particularly severe when the fuel cell experiences repetitive start-stop cycles. Therefore, specific countermeasures against catalyst layer carbon oxidation are required, especially for automotive and backup power applications, where the startup/shutdown rate is considerably high. The authors evaluated a basic design that uses a stack shunt. A properly modified control protocol, which includes the stack shunt, is able to avoid high cathode potential peaks, which are known to accelerate catalyst carbon support corrosion and its negative effects. During two separate durability tests, one adopting the shunt design and another using nonprotected shutdown, a 24-cell stack was subjected to continuous starts and stops for several months and its performance constantly monitored. The results show that when the shunt is used, there is a 37% reduction in the voltage degradation rate for each startup/shutdown cycle and a two-fold increase in the number of startup/shutdown cycles before an individual cell reached the specified “end of life” voltage criteria. Furthermore, ex situ FE-SEM analysis revealed cathode catalyst layer thinning, which is an indication that the emerging degradation mechanism is the catalyst support carbon corrosion, as expected. This provides further support that the constant voltage degradation rate typically experienced in PEMFCs can be primarily attributed to the catalyst support carbon corrosion rate. The proposed shunt protocol is very cost effective and does not require any substantial changes in the system. For this reason, its adoption is recommended as a viable method to decrease the catalyst support carbon corrosion rate and extend the operating life of the PEMFC stack.

Daniel F. Walczyk, Jaskaran S. Sangra

Journal of Fuel Cell Science and Technology • 2010

The feasibility of an alternative fuel cell architecture, called a ribbon membrane electrode assembly (MEA), is demonstrated for low-temperature polymer electrolyte membrane (PEM) fuel cells used in portable power applications by comparing it to a traditional bipolar “stack” architecture. A ribbon MEA consists of adjacent PEM cells sharing a common gas diffusion layer to allow for lateral electrical current flow and an integral gas-tight, conductive interconnect/seal, where adjacent cells meet to prevent reactant gas leakage. The resulting lateral arrangement of MEAs can be used to supply all MEAs simultaneously instead of individual bipolar plates with flow fields for a stack. A pair of two-cell ribbon MEAs, with and without an interconnect/seal, were designed, prototyped, and sealed by thermal pressing. The MEAs were clamped in a two-piece box fixture to provide reactant gases on the anode and cathode sides, hooked to a fuel cell (FC) test stand and yielded an open circuit voltage (OCV) of 1.43 V with an interconnect/seal and 0.6 V without. A two-cell bipolar stack PEMFC with identical MEA specifications had an OCV of 1.86 V. Polarization curves for the ribbon MEA with interconnect/seal showed the sensitivity of performance to clamping pressure and positioning of the copper current collectors. The ribbon MEA polarization curve was also shifted downward by 0.42 V as compared with that of the traditional stack, and suspected causes (e.g., gas leaking) are attributable to the nonoptimal test fixture design. Hence, the ribbon MEA architecture is shown to be feasible. Future work suggested includes improvements to the test fixture design, development of automated manufacturing capabilities for high volume production, and demonstration of a multicell (>2) ribbon MEA PEMFC design.

Anirban Roy, Frida Roenning, Douglas Aaron et al.

ECS Meeting Abstracts • 2020

Conventional research and diagnostic techniques for fuel cells and electrolyzers, such as polarization curves and EIS measurements, predominantly probe macroscopic performance characteristics. The works of Schuler, et al. [ 1 ] have given a detailed understanding of transport mechanisms inside a polymer electrolyte water electrolyzer (PEWE) by drawing extensively on such ex-situ techniques. However, these techniques cannot be used to probe in-situ behaviors of a PEWE. A need for reliable experimental data that captures in-situ spatial and temporal current distribution is the motivation for the segmented cell used here. Current distribution measurement in PEWEs was performed by Bender et al. [ 2 , 3 ] while Mench and coworkers pioneered the technique in similar flowing electrochemical systems [ 4 , 5 ]; a major innovation was inclusion of a printed-circuit board (PCB) with an array of shunt resistors attached to each segment as shown in Figure 1a. The advantage of this design is that, although the PCB and flow-field are segmented and electronically isolated, the other components of the cell are not. However, this design is subject to error since current can spread laterally through the porous transport layer (PTL) as it passes from the catalyst layer to the segmented flow field. Since activity at the catalyst layer is of great interest, understanding current spread is a critical step to utilizing current distribution measurements. This work focuses on characterizing the lateral current spread through PTLs. Work by Philips, Ulsh, and Bender [ 3 ], showed that the experimental setup could be modified with the help of masks to characterize lateral current spread through the PTL. A set of experiments was thus designed to investigate current spread through the porous transport layer both “inward” and “outward” from a flow field segment. The goal of these experiments is to quantify current spread, allowing correction of its contribution to obfuscating measurement of current generated in the catalyst layer. High current was detected for the PCB segment corresponding to the unmasked area as expected, but substantial current was measured around the exposed area, as well (Figure 1b). If there was zero outward current spread, no current would be measured anywhere away from the single segment area generating current. Figure 1c shows average current density as a function of radial distance from a generating spot; Figure 1d plots normalized current density as a function of radial distance. This set provides calibration for how much current spread laterally outwards as detected at points located away from a current-generating area. Similarly, inward contributions were also mapped. These experiments were also carried out for two types of PTL – Ti-foil-based thin LGDLs [ 6 ] and Ti-based felt PTLs. Preliminary observations indicate that lateral current spread in the Ti-felt-based LGDLs is less than that of the Ti-based foil LGDLs. This work quantifies the lateral current spread seen inside a LGDL and also lays the groundwork to correct current spread recorded in a spatially-resolved current distribution measurement technique. It is part of DOE project #DE-EE0008426 "Developing novel electrodes with ultralow catalyst loading for high-efficiency hydrogen production in proton exchange membrane electrolyzer cells." References Schuler, T., T.J. Schmidt, and F.N. Büchi, Polymer Electrolyte Water Electrolysis: Correlating Performance and Porous Transport Layer Structure: Part II. Electrochemical Performance Analysis. Journal of The Electrochemical Society, 2019. 166 (10): p. F555-F565. Reshetenko, T.V., et al., A segmented cell approach for studying the effects of serpentine flow field parameters on PEMFC current distribution. Electrochimica Acta, 2013. 88 : p. 571-579. Phillips, A., et al., Utilizing a Segmented Fuel Cell to Study the Effects of Electrode Coating Irregularities on PEM Fuel Cell Initial Performance. Fuel Cells, 2017. 17 (3): p. 288-298. Clement, J.T., D.S. Aaron, and M.M. Mench, In Situ Localized Current Distribution Measurements in All-Vanadium Redox Flow Batteries. Journal of The Electrochemical Society, 2015. 163 (1): p. A5220-A5228. Ertugrul, T.Y., et al., In-situ current distribution and mass transport analysis via strip cell architecture for a vanadium redox flow battery. Journal of Power Sources, 2019. 437 : p. 226920. Mo, J., et al., Discovery of true electrochemical reactions for ultrahigh catalyst mass activity in water splitting. Science Advances, 2016. 2 (11): p. e1600690. Figure 1

Denise A. McKahn, Xizhu Zhao

ASME 2012 10th International Conference on Fuel Cell Science, Engineering and Technology • 2012

Numerous applications exist requiring power for small loads (<5W) with minimal mass operating in extreme ambient conditions. Making progress toward reducing stack mass, we investigate the influence of flow field channel depth and endplate compression on cell performance. The best performance was found at endplate compressions of 139 psi, cathode channel depths of 0.032 in and anode channel depths of 0.032 in. The maximum power mass-density achieved with these 4.84 cm2 cells was 16.8 mW/g in a single cell stack. If deployed in a multicell stack, this same performance would translate to a power mass-density of 45.3 mW/g, nearing the performance of off-the-shelf lithium ion batteries (approximately 70 mW/g).

Koichi Matsutani, Katsuichiro Hayakawa, Tomoyuki Tada

Platinum Metals Review • 2010

To investigate the effect of load cycling, platinum (Pt) and platinum-cobalt (PtCo) fuel cell catalysts with different particle sizes were prepared and evaluated for their durability against load cycling. The particle size of the Pt and PtCo catalysts was controlled by changing the catalyst loading and by applying heat treatment. Pt catalysts with particle sizes of 2–3 nm and 4–5 nm and PtCo catalysts with sizes of 3–4 nm, 4–5 nm and 7–8 nm were obtained. A potential sweep from 0.65 V to 1.05 V was applied to the cathode of membrane electrode assemblies (MEAs) prepared with these catalysts,and the degradation of their mass activity and cell voltage were evaluated. As a result of this investigation, it was found that Pt catalysts with particle sizes of 4–5 nm and PtCo catalysts of particle sizes 7–8 nm showed better stability against potential sweep, with the Pt catalysts of sizes 4–5 nm showing the best stability of all the catalysts tested.