Porous Hollow Fiber Nickel Electrodes for Effective Supply and Reduction of Carbon Dioxide to Methane through Microbial Electrosynthesis

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.