In situ synthetic H2 on composite cathode surface for CH4 production from CO2 in microbial electrosyntshesis

Abstract

Microbial electrosynthesis (MES) is an innovative technology that employs microbes to synthesize chemicals by reducing CO2.This study explores the CH4 production performance at different cathodic reduction potentials in MES. In this study, in situ H2 production on the surface of composite electrode was realized by regulating cathode potential. Pathway for H2-mediated CH4 synthesis was the main synthesis pathway, but it was susceptible to interfere from the external environment (such as cathode potential, pH). The optimal CH4 production potential was −1.0 V vs Ag/AgCl, meanwhile the CH4 synthesis rate was 58 ± 0.4 mLm−2d−1 and the CE was 67 ± 0.5%. Excessively high reduction potentials (−1.4 V vs Ag/AgCl) reduce the activity of microbial populations at the cathode. Synergistic interactions between H2-producing bacteria (Hydrogenophaga, Clostridium, Enterobacter, and Escherichia coli) and Hydrogenotrophic methanogens (Methanobacterium and Methanomassiliicocus) promoted efficient synthesis of CH4. These insights provide new perspectives on reactor operation, thus contributing to the efficiency of MES.