Enhancing CO 2 -reduction methanogenesis in microbial electrosynthesis: Role of oxygen-containing groups on carbon-based cathodes

Microbial electrosynthesis is a promising technology that recovers energy from wastewater while converting CO into CH . Constructing a biocathode with both strong H -mediated and direct electron transfer capacities is crucial for efficient startup and long-term stable CH production. This study found that introducing carboxyl groups onto the cathode effectively enhanced both electron transfer pathways, improving the reduction rate and coulombic efficiency of CH production and increasing the CH yield by 2-3 times. Carboxyl groups decreased the overpotential for H evolution and increased current density, thereby enhancing H -mediated electron transfer. Additionally, carboxyl groups increased the relative abundance of Methanosaeta by 3%-10%, doubled the protein content in extracellular polymeric substances, and boosted the expression of cytochrome c-related genes, thereby enhancing direct electron transfer capacity. These findings present a novel and efficient approach for constructing a stable, high-performance biocathode, contributing to energy recovery and CO fixation.