Visible light-driven dual photoelectrode microbial electrosynthesis using BiVO4-RuO2-IrO2 on Ti mesh photoanode and ZIF-67/g-C3N4 on carbon felt photocathode for the efficient reduction of CO2 into acetate

Microbial electrosynthesis (MES) systems integrated with solar energy (photoelectrode-assisted MES) represent an attractive method for the fixation of CO2 through microbial electrochemical processes. In this study, BiVO4-RuO2-IrO2/Ti with long-term stability and corrosion resistance was used as photoanode through the electrophoretic deposition of BiVO4 on RuO2-IrO2/Ti mesh, significantly reducing the charge recombination rate and enhancing the oxygen evolution reaction (OER) ability. Simultaneously, the ZIF-67/g-C3N4 photocathode can significantly increase CO2 absorption and hydrogen production by enhancing electron–hole separation ability under visible light. Consequently, the MES system with the BiVO4-RuO2-IrO2/Ti anode and ZIF-67/g-C3N4 photocathode obtained an acetate yield of 0.46 g/L/d at −0.9 V versus Ag/AgCl within 14 days. This value was 4.6 times that under dark conditions. The solar-to-acetate conversion efficiency was determined to be 1.52%. Furthermore, the MES with dual photoelectrode still obtained an acetate yield of 0.09 g/L/d at −0.6 V versus Ag/AgCl. These results showed that the MES with the BiVO4-RuO2-IrO2/Ti photoanode and ZIF-67/g-C3N4 photocathode reduced OER overpotential, increased electron transport rate, and improved CO2 supply for the simultaneous supplementation of substrates and electrons in MES. This work provides a new strategy for constructing efficient photoelectrodes in MES to achieve highly efficient chemical generation for CO2 transformation under solar light.