Sovik Das, Swati Das, Makarand M. Ghangrekar

Process Biochemistry • 2020

Pier‐Luc Tremblay, Neda Faraghiparapari, Tian Zhang

Catalysts • 2019

Microbial electrosynthesis (MES) is a process where bacteria acquire electrons from a cathode to convert CO2 into multicarbon compounds or methane. In MES with Sporomusa ovata as the microbial catalyst, cathode potential has often been used as a benchmark to determine whether electron uptake is hydrogen-dependent. In this study, H2 was detected by a microsensor in proximity to the cathode. With a sterile fresh medium, H2 was produced at a potential of −700 mV versus Ag/AgCl, whereas H2 was detected at −500 mV versus Ag/AgCl with cell-free spent medium from a S. ovata culture. Furthermore, H2 evolution rates were increased with potentials lower than −500 mV in the presence of cell-free spent medium in the cathode chamber. Nickel and cobalt were detected at the cathode surface after exposure to the spent medium, suggesting a possible participation of these catalytic metals in the observed faster hydrogen evolution. The results presented here show that S. ovata-induced alterations of the cathodic electrolytes of a MES reactor reduced the electrical energy required for hydrogen evolution. These observations also indicated that, even at higher cathode potentials, at least a part of the electrons coming from the electrode are transferred to S. ovata via H2 during MES.

Jeannine C. Mayr, Jan‐Hendrik Grosch, Lena Hartmann et al.

ChemSusChem • 2019

Chiral alcohols constitute important building blocks that can be produced enantioselectively by using nicotinamide adenine dinucleotide (phosphate) [NAD(P)H]-dependent oxidoreductases. For NAD(P)H regeneration, electricity delivers the cheapest reduction equivalents. Enzymatic electrosynthesis suffers from cofactor and enzyme instability, whereas microbial electrosynthesis (MES) exploits whole cells. Here, we demonstrate MES by using resting Escherichia coli as biocatalytic chassis for a production platform towards fine chemicals through electric power. This chassis was exemplified for the synthesis of chiral alcohols by using a NADPH-dependent alcohol dehydrogenase from Lactobacillus brevis for synthesis of (R)-1-phenylethanol from acetophenone. The E. coli strain and growth conditions affected the performance. Maximum yields of (39.4±5.7) % at a coulombic efficiency of (50.5±6.0) % with enantiomeric excess >99 % was demonstrated at a rate of (83.5±13.9) μm h -1 , confirming the potential of MES for synthesis of high-value compounds.

Gunda Mohanakrishna, Ibrahim M. Abu Reesh, Karolien Vanbroekhoven et al.

The Science of The Total Environment • 2020

Paniz Izadi, Jean‐Marie Fontmorin, Alexiane Godain et al.

npj Biofilms and Microbiomes • 2020

Cathode-driven applications of bio-electrochemical systems (BESs) have the potential to transform CO 2 into value-added chemicals using microorganisms. However, their commercialisation is limited as biocathodes in BESs are characterised by slow start-up and low efficiency. Understanding biosynthesis pathways, electron transfer mechanisms and the effect of operational variables on microbial electrosynthesis (MES) is of fundamental importance to advance these applications of a system that has the capacity to convert CO 2 to organics and is potentially sustainable. In this work, we demonstrate that cathodic potential and inorganic carbon source are keys for the development of a dense and conductive biofilm that ensures high efficiency in the overall system. Applying the cathodic potential of -1.0 V vs. Ag/AgCl and providing only gaseous CO 2 in our system, a dense biofilm dominated by Acetobacterium (ca. 50% of biofilm) was formed. The superior biofilm density was significantly correlated with a higher production yield of organic chemicals, particularly acetate. Together, a significant decrease in the H 2 evolution overpotential (by 200 mV) and abundant nifH genes within the biofilm were observed. This can only be mechanistically explained if intracellular hydrogen production with direct electron uptake from the cathode via nitrogenase within bacterial cells is occurring in addition to the commonly observed extracellular H 2 production. Indeed, the enzymatic activity within the biofilm accelerated the electron transfer. This was evidenced by an increase in the coulombic efficiency (ca. 69%) and a 10-fold decrease in the charge transfer resistance. This is the first report of such a significant decrease in the charge resistance via the development of a highly conductive biofilm during MES. The results highlight the fundamental importance of maintaining a highly active autotrophic Acetobacterium population through feeding CO 2 in gaseous form, which its dominance in the biocathode leads to a higher efficiency of the system.

Siddharth Gadkari, Behzad Haji Mirza Beigi, Nabin Aryal et al.

RSC Advances • 2021

Microbial electrosynthesis (MES) is an innovative technology for electricity driven microbial reduction of carbon dioxide (CO 2 ) to useful multi-carbon compounds. This study assesses the cradle-to-gate environmental burdens associated with acetic acid (AA) production via MES using graphene functionalized carbon felt cathode. The analysis shows that, though the environmental impact for the production of the functionalized cathode is substantially higher when compared to carbon felt with no modification, the improved productivity of the process helps in reducing the overall impact. It is also shown that, while energy used for extraction of AA is the key environmental hotspot, ion-exchange membrane and reactor medium (catholyte & anolyte) are other important contributors. A sensitivity analysis, describing four different scenarios, considering either continuous or fed-batch operation, is also described. Results show that even if MES productivity can be theoretically increased to match the highest space time yield reported for acetogenic bacteria in a continuous gas fermenter (148 g L -1 d -1 ), the environmental impact of AA produced using MES systems would still be significantly higher than that produced using a fossil-based process. Use of fed-batch operation and renewable (solar) energy sources do help in reducing the impact, however, the low production rates and overall high energy requirement makes large-scale implementation of such systems impractical. The analysis suggests a minimum threshold production rate of 4100 g m -2 d -1 , that needs to be achieved, before MES could be seen as a sustainable alternative to fossil-based AA production.

Haixia Liu, Tian‐shun Song, Kangqing Fei et al.

Bioresources and Bioprocessing • 2018

The conversion of CO2 into high value-added products has a very important environmental and economic significance. Microbial electrosynthesis (MES) is a promising technology, which adopts a bioelectrochemical system to transform CO2 into organic chemicals. In this study, Clostridium scatologenes ATCC 25775T, an anaerobic acetogenic bacterium, demonstrated its utility as a biocatalyst in a MES system, for the first time. With the cathodic potential of the MES system decreased from − 0.6 to − 1.2 V (vs. Ag/AgCl), the current density of the MES, and the production of organic chemicals, increased. Combining the genetic analysis and the results of the wet lab experiments, we believe C. scatologenes may accept electrons directly from the cathode to reduce CO2 into organic compounds at a potential of − 0.6 V. The acetic and butyric acid reached a maximum value of 0.03 and 0.01 g/L, respectively, and the maximum value of total coulombic efficiency was about 84%, at the potential of − 0.6 V. With the decrease in cathodic potentials, both direct electron transfer and exogenous electron shuttle, H2 might be adopted for the C. scatologenes MES system. At a potential of − 1.2 V, acetic acid, butyric acid and ethanol were detected in the cathodic chamber, with their maximum values increasing to 0.44, 0.085 and 0.015 g/L, respectively. However, due to the low H2 utilization rate by the C. scatologenes planktonic cell, the total coulombic efficiency of the MES system dropped to 37.8%. Clostridium scatologenes is an acetogenic bacterium which may fix CO2 through the Wood–Ljungdahl pathway. Under H2 fermentation, C. scatologenes may reduce CO2 to acetic acid, butyric acid and ethanol. It can also be used as the biocatalyst in MES systems.

Sylvia Gildemyn, Kristof Verbeeck, Robbe Jansen et al.

Bioresource Technology • 2016

Jörg S. Deutzmann, Frauke Kracke, Wenyu Gu et al.

Environmental Science & Technology • 2022

Microbial electrosynthesis (MES) of acetate is a process using electrical energy to reduce CO 2 to acetic acid in an integrated bioelectrochemical system. MES powered by excess renewable electricity produces carbon-neutral acetate while benefitting from inexpensive but intermittent energy sources. Interruptions in electricity supply also cause energy limitation and starvation of the microbial cells performing MES. Here, we studied the effect of intermittent electricity supply on the performance of hydrogen-mediated MES of acetate. Thermoanaerobacter kivui produced acetic acid for more than 4 months from intermittent electricity supplied in 12 h on-off cycles in a semicontinuously-fed MES system. After current interruptions, hydrogen utilization and acetate synthesis rates were severely diminished. They did not recover to the steady-state rates of continuous MES within the 12 h current-on period under most conditions. Accumulating high product (acetate) concentration exacerbated this effect and prolonged recovery. However, supply of a low background current of 1-5% of the maximum current during "off-times" reduced the impact of current interruptions on subsequent MES performance. This study presents sustained MES at a rate of up to 2 mM h -1 acetate at an average concentration of 60-90 mM by a pure thermophilic microbial culture powered by intermittent electricity. We identified product inhibition of accumulating acetic acid as a key challenge to improving the efficiency of intermittently powered MES.

Paniz Izadi, Jean‐Marie Fontmorin, Bernardino Virdis et al.

Applied Energy • 2020

Reduction of CO2 to acetate in microbial electrosynthesis has been widely studied. However, the selective and quantitative production of longer chain chemicals and biofuels is still a bottleneck. Lack of sufficient energy provided by only the cathode electrode in Bio-electrochemical systems during chain elongation is one of the key challenges. It is assumed that additional electron donors than a polarised cathode is required to steer the production towards longer chain of carboxylates than acetate. In this study, formate and ethanol were supplied separately in the reactors fed by CO2 for 45 days in addition to the cathodes poised at −1.0 V vs. Ag/AgCl to investigate their effect on production. Although acetate was still the major product, supplying electron donors directed the production towards more diverse and longer chain organic chemicals than that in presence of the polarised cathode only. Significant improvement in the production of butyrate (×3.8 increase in maximum concentration) and butanol (maximum of 6.8 ± 0.3 mmol C L−1) was observed after supplying formate, while ethanol increased the diversity of the products. Supplying formate and ethanol in reactors for another 30 days under open circuit potential clarified that only ethanol could provide sufficient energy for butyrate production from acetate in the absence of polarised cathode, which reached the highest butyrate concentration of 19.1 ± 2.3 mmol C L−1. Formate was only consumed in presence of polarised cathode. It is proposed in our study that production of C4 products in presence of only cathodic electrode or cathodic electrode and formate could be associated to initial reduction of acetate to ethanol, consumed for production of C4 products through acetate. Trace levels of caproate and hexanol were detected in both reactors supplied with formate and ethanol only in the presence of polarised cathode.

Shihao Tian, Haoqi Wang, Zhiwei Dong et al.

Biotechnology for Biofuels • 2019

Coupling a HER catalyst to a cathode of MES system is a promising strategy for improving MES efficiency.

Yinbo Xiang, Guangli Liu, Renduo Zhang et al.

Bioresource Technology • 2017

Suman Bajracharya, Bart van den Burg, Karolien Vanbroekhoven et al.

Electrochimica Acta • 2017

Shuwei Li, Sakuntala Mutyala, Young Eun Song et al.

Bioresource Technology • 2020

Haiping Luo, Jiaxin Qi, Meizhou Zhou et al.

Bioresource Technology • 2020

Jun Li, Zhuo Li, Shuai Xiao et al.

Journal of CO2 Utilization • 2019

Nabin Aryal, Lulu Wan, Marc H. Overgaard et al.

Bioelectrochemistry • 2019

Xenia Christodoulou, Sharon B. Velasquez‐Orta

Environmental Science & Technology • 2016

Microbial electrosynthesis (MES) and anaerobic fermentation (AF) are two biological processes capable of reducing CO 2 , CO, and water into acetic acid, an essential industrial reagent. In this study, we evaluated investment and production costs of acetic acid via MES and AF, and compared them to industrial chemical processes: methanol carbonylation and ethane direct oxidation. Production and investment costs were found high-priced for MES (1.44 £/kg, 1770 £/t) and AF (4.14 £/kg, 1598 £/t) because of variable and fixed costs and low production yields (100 t/y) compared to methanol carbonylation (0.26 £/kg, 261 £/t) and ethane direct oxidation (0.11 £/kg, 258 £/t). However, integrating AF with MES would reduce the release of CO 2 , double production rates (200 t/y), and decrease investment costs by 9% (1366 £/t). This resulted into setting the production costs at 0.24 £/kg which is currently market competitive (0.48 £/kg). This economically feasible bioprocess produced molar flow rates of 4550 mol per day from MES and AF independently. Our findings offer a bright opportunity toward the use and scale-up of MES and AF for an economically viable acetic acid production process.

Wenfang Cai, Kai Cui, Zhuangzhuang Liu et al.

Chemical Engineering Journal • 2021

Marzuqa Quraishi, Kayinath Wani, Soumya Pandit et al.

Fermentation • 2021

Microbial electrocatalysis reckons on microbes as catalysts for reactions occurring at electrodes. Microbial fuel cells and microbial electrolysis cells are well-known in this context; both prefer the oxidation of organic and inorganic matter for producing electricity. Notably, the synthesis of high energy-density chemicals (fuels) or their precursors by microorganisms using bio-cathode to yield electrical energy is called Microbial Electrosynthesis (MES), giving an exceptionally appealing novel way for producing beneficial products from electricity and wastewater. This review accentuates the concept, importance and opportunities of MES, as an emerging discipline at the nexus of microbiology and electrochemistry. Production of organic compounds from MES is considered as an effective technique for the generation of various beneficial reduced end-products (like acetate and butyrate) as well as in reducing the load of CO2 from the atmosphere to mitigate the harmful effect of greenhouse gases in global warming. Although MES is still an emerging technology, this method is not thoroughly known. The authors have focused on MES, as it is the next transformative, viable alternative technology to decrease the repercussions of surplus carbon dioxide in the environment along with conserving energy.

Yinbo Xiang, Guangli Liu, Renduo Zhang et al.

Bioresource Technology • 2017

Frauke Kracke, Jörg S. Deutzmann, Buddhinie Srimali Jayathilake et al.

Frontiers in Microbiology • 2021

The efficient delivery of electrochemically in situ produced H 2 can be a key advantage of microbial electrosynthesis over traditional gas fermentation. However, the technical details of how to supply large amounts of electric current per volume in a biocompatible manner remain unresolved. Here, we explored for the first time the flexibility of complex 3D-printed custom electrodes to fine tune H 2 delivery during microbial electrosynthesis. Using a model system for H 2 -mediated electromethanogenesis comprised of 3D fabricated carbon aerogel cathodes plated with nickel-molybdenum and Methanococcus maripaludis , we showed that novel 3D-printed cathodes facilitated sustained and efficient electromethanogenesis from electricity and CO 2 at an unprecedented volumetric production rate of 2.2 L CH4 /L catholyte /day and at a coulombic efficiency of 99%. Importantly, our experiments revealed that the efficiency of this process strongly depends on the current density. At identical total current supplied, larger surface area cathodes enabled higher methane production and minimized escape of H 2 . Specifically, low current density (<1 mA/cm 2 ) enabled by high surface area cathodes was found to be critical for fast start-up times of the microbial culture, stable steady state performance, and high coulombic efficiencies. Our data demonstrate that 3D-printing of electrodes presents a promising design tool to mitigate effects of bubble formation and local pH gradients within the boundary layer and, thus, resolve key critical limitations for in situ electron delivery in microbial electrosynthesis.

Zaiqiang Wu, Junsong Wang, Jun Liu et al.

Microbial Cell Factories • 2019

The strain T110(pMtrABC, pFccA-CymA, pBTCA) is to our best knowledge the first electroactive microbial cell factory engineered to directly utilize electricity for the production of a specific product. Due to the versatility of the E. coli platform, this pioneering research opens the possibility of engineering various other cell factories to utilize electricity for bioproduction.

Zhiwei Dong, Haoqi Wang, Shihao Tian et al.

Bioresource Technology • 2018

Young Eun Song, Abdelrhman Mohamed, Changman Kim et al.

Chemical Engineering Journal • 2021

Sovik Das, Ludo Diels, Deepak Pant et al.

Journal of The Electrochemical Society • 2020

There has been a considerable increment in the atmospheric CO 2 concentration, which has majorly contributed to the problem of global warming. This issue can be extenuated by effectively developing microbial electrosynthesis (MES) for the sequestration of CO 2 with the concurrent production of biochemical and biofuels. Though the MES technology is in its infancy, it has exhibited enormous potential for sustainable mitigation of CO 2 and bioelectrosynthesis of multi-carbon organic compounds. The problem of storage of excess renewable electrical energy by conventional means can also be alleviated by employing MES, which stores it in the form of C–C bonds of chemicals. This review focuses on the various aspects of MES and recent developments made in this field to overcome its bottlenecks, such as the lower yield of organic compounds, separation of products of higher chain organic compounds, etc. In particular, the microbial catalysts and cathode materials employed in MES have also been emphasized. Keeping in mind the potential of this innovative technology, researchers should focus on improving the yield of MES by developing novel low-cost cathode materials and discovering efficient and robust micro-organisms, which would be a significant step forward towards the further advancement of this technology.

Bin Bian, Manal Alqahtani, Krishna P. Katuri et al.

Journal of Materials Chemistry A • 2018

Nickel porous hollow fibers coated with CNTs acted as both a gas transfer membrane for CO 2 delivery and a cathode for providing electrons to microbial catalysts, achieving improved CO 2 conversion to value-added products in microbial electrosynthesis.

Moumita Roy, Ravineet Yadav, P. Chiranjeevi et al.

Bioresource Technology • 2020

Linpeng Yu, Yong Yuan, Jiahuan Tang et al.

Bioelectrochemistry • 2017

Xiaoli Chen, Yingxiu Cao, Feng Li et al.

ACS Catalysis • 2018

Microbial electrosynthesis (MES) is a promising technology to reduce carbon dioxide using inward electron transfer mechanisms to synthesize value-added chemicals with microorganisms as electrocatalysts and electrons from cathodes as reducing equivalents. To enhance CO2 assimilation in Ralstonia eutropha, a formate dehydrogenase (FDH) assisted MES system was constructed, in which FDH catalyzed the reduction of CO2 to formate in the cathodic chamber. Formate served as the electron carrier to transfer electrons derived from cathodes into R. eutropha. To enable efficient formation of formate from CO2, neutral red (NR) was used to facilitate the extracellular regeneration of NADH, the cofactor of FDH. Meanwhile, NR also played an essential role as electron shuttle to directly deliver electrons from cathodes into R. eutropha to increase the level of intracellular reducing equivalents, thus facilitating the efficiency of MES. On the other hand, the Calvin–Benson–Bassham (CBB) cycle was further engineered by the heterologous expression of the ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) in R. eutropha, which strengthened the CBB pathway for CO2 fixation. Upon application of the cathode potential at −0.6 V (vs Ag/AgCl) in the MES system with the genetically engineered R. eutropha, 485 ± 13 mg/L poly(3-hydroxybutyrate) (PHB) was obtained, which was ∼3 times that synthesized by the control (165 ± 8 mg/L), i.e., the wild-type R. eutropha in the absence of FDH and NR.

Igor Vassilev, Frauke Kracke, Stefano Freguia et al.

Chemical Communications • 2019

A microbial electrosynthesis cell comprising two biological cathode chambers sharing the same anode compartment is used to promote the production of C2-C4 carboxylic acids and alcohols from carbon dioxide. Each cathode chamber provides ideal pH conditions to favor acetogenesis/carbon chain elongation (pH = 6.9), and solventogenesis (pH = 4.9), respectively, without the requirement of external acid/base dosing.

Ludovic Jourdin, J. Sousa, Niels van Stralen et al.

Applied Energy • 2020

Microbial electrosynthesis (MES) allows carbon-waste and renewable electricity valorization into industrially-relevant chemicals. MES has received much attention in laboratory-scale research, although a techno-economic-driven roadmap towards validation and large-scale demonstration of the technology is lacking. In this work, two main integrated systems were modelled, centered on (1) MES-from-CO2 and (2) MES from short-chain carboxylates, both for the production of pure, or mixture of, acetate, n–butyrate, and n–caproate. Twenty eight key parameters were identified, and their impact on techno-economic feasibility of the systems assessed. The main capital and operating costs were found to be the anode material cost (59%) and the electricity consumption (up to 69%), respectively. Under current state-of-the-art MES performance and economic conditions, these systems were found non-viable. However, it was demonstrated that sole improvement of MES performance, independent of improvement of non-technological parameters, would result in profitability. In otherwise state-of-the-art conditions, an improved electron selectivity (≥36%) towards n-caproate, especially at the expense of acetate, was showed to result in positive net present values (i.e. profitability; NPV). Cell voltage, faradaic efficiency, and current density also have significant impact on both the capital and operating costs. Variation in electricity cost on overall process feasibility was also investigated, with a cost lower than 0.045 € kWh−1 resulting in positive NPV of the state-of-the-art scenario. Maximum purification costs were also determined to assess the integration of a product’s separation unit, which was showed possible at positive NPV. Finally, we briefly discuss CO2 electroreduction versus MES, and their potential market complementarities.

Victoria Flexer, Ludovic Jourdin

Accounts of Chemical Research • 2020

Carbon-based products are crucial to our society, but their production from fossil-based carbon is unsustainable. Production pathways based on the reuse of CO 2 will achieve ultimate sustainability. Furthermore, the costs of renewable electricity production are decreasing at such a high rate, that electricity is expected to be the main energy carrier from 2040 onward. Electricity-driven novel processes that convert CO 2 into chemicals need to be further developed. Microbial electrosynthesis is a biocathode-driven process in which electroactive microorganisms derive electrons from solid-state electrodes to catalyze the reduction of CO 2 or organics and generate valuable extracellular multicarbon reduced products. Microorganisms can be tuned to high-rate and selective product formation. Optimization and upscaling of microbial electrosynthesis to practical, real life applications is dependent upon performance improvement while maintaining low cost. Extensive biofilm development, enhanced electron transfer rate from solid-state electrodes to microorganisms and increased chemical production rate require optimized microbial consortia, efficient reactor designs, and improved cathode materials. This Account is about the development of different electrode materials purposely designed for improved microbial electrosynthesis: NanoWeb-RVC and EPD-3D. Both types of electrodes are biocompatible, highly conductive three-dimensional hierarchical porous structures. Both chemical vapor deposition (CVD) and electrophoretic deposition were used to grow homogeneous and uniform carbon nanotube layers on the honeycomb structure of reticulated vitreous carbon. The high surface area to volume ratio of these electrodes maximizes the available surface area for biofilm development, i.e., enabling an increased catalyst loading. Simultaneously, the nanostructure makes it possible for a continuous electroactive biofilm to be formed, with increased electron transfer rate and high Coulombic efficiencies. Fully autotrophic biofilms from mixed cultures developed on both types of electrodes rely on CO 2 as the sole carbon source and the solid-state electrode as the unique energy supply. We present first the synthesis and characteristics of the bare electrodes. We then report the outstanding performance indicators of these novel biocathodes: current densities up to -200 A m -2 and acetate production rates up to 1330 g m -2 day -1 , with electron and CO 2 recoveries into acetate being very close to 100% for mature biofilms. The performance indicators are still among the highest reported by either purposely designed or commercially available biocathodes. Finally, we made use of the titration and off-gas analysis sensor (TOGA) to elucidate the electron transfer mechanism in these efficient biocathodes. Planktonic cells in the catholyte were found irrelevant for acetate production. We identified the electron transfer to be mediated by biologically induced H 2 . H 2 is not detected in the headspace of the reactors, unless CO 2 feeding is interrupted or the cathodes sterilized. Thus, the biofilm is extremely efficient in consuming the generated H 2 . Finally, we successfully demonstrated the use of a synthetic biogas mixture as a CO 2 source. We thus proved the potential of microbial electrosynthesis for the simultaneous upgrading of biogas, while fixating CO 2 via the production of acetate.

Mélida del Pilar Anzola-Rojas, Marcelo Zaiat, Ernesto Rafael González et al.

Bioresource Technology • 2018

Na Chu, Hao Wen, Qinglian Wu et al.

Engineering • 2021

Microbial electrosynthesis (MES) employs microbial catalysts and electrochemistry to enhance CO2 bioconversion to organics with concurrent waste biorefining capability. The aim of this review is to comprehensively discuss the current state of the art and prospects of medium chain fatty acids (MCFAs) production in MES from CO2 and organic wastes. Fundamental mechanisms and development of MCFAs production via conventional fermentation are introduced as well. Studies on MCFAs production in MES are summarized, highlighting the strategy of multiple-electron donors (EDs). Challenges for MCFAs production in MES from CO2 are presented, and the primary discussions included methanogenesis inhibition, adenosine triphosphate (ATP) limitations of acetogens, and production of limited EDs via solventogenesis. Possible applications of electrochemical approaches to promote the bioconversion of actual waste materials with MCFAs production are analyzed. Finally, future directions are explored, including multi-stage reactions, substrate supply, product extraction, and microbial pathways.

J. Annie Modestra, S. Venkata Mohan

Journal of CO2 Utilization • 2017

Fanying Kong, Hong‐Yu Ren, Spyros G. Pavlostathis et al.

Renewable and Sustainable Energy Reviews • 2020

Raúl Mateos, Adrián Escapa, M. Isabel San-Martín et al.

Journal of Energy Chemistry • 2019

Manal Alqahtani, Krishna P. Katuri, Suman Bajracharya et al.

Advanced Functional Materials • 2018

Abstract Microbial electrochemical reduction of CO 2 gas to value‐added chemical products requires the development of an electrode architecture with a three‐phase interface for efficient mass transport. A hybrid bioinorganic system for CO 2 reduction to CH 4 is developed by coupling a new electrode architecture with enriched methanogenic community. The novel electrode design consists of porous nickel hollow fibers, which act as an inorganic electrocatalyst for hydrogen generation from proton reduction and as a gas‐transfer membrane for direct CO 2 delivery to CO 2 ‐fixing hydrogenotrophic methanogens (biological catalyst) on the cathode through the pores of the hollow fibers. These unique features of the electrode create a suitable environment for the enrichment of methanogens, which utilize the hydrogen as a source of reducing equivalents for the conversion of CO 2 to CH 4 . The performance of the nickel electrode is tested in microbial electrosynthesis cells operated at cathode potential of −1 V versus Ag/AgCl, achieving high faradaic efficiency of 77% for CH 4 . The superior performance of the hybrid bioinorganic system is attributed to the electrode architecture, which provides a three‐phase boundary for gas–liquid reactions, with the reactions supported by the inorganic and biological catalysts.

Gunda Mohanakrishna, Karolien Vanbroekhoven, Deepak Pant

Journal of CO2 Utilization • 2016