Enhancing CH₄ production in microbial electrolysis cells: Optimizing electric field via carbon cathode resistivity

Microbial electrolysis cells (MECs) are increasingly recognized as a promising technology for converting CO₂ to CH₄, offering the dual benefits of energy recovery from organic wastewater and CO₂ emission reduction. A critical aspect of this technology is the enhancement of the electron-accepting capacity of the methanogenic biocathode to improve CH₄ production efficiency. This study demonstrates that adjusting the cathode resistivity is an effective way to control the electric field intensity, thereby enhancing the electron accepting capacity and CH₄ production. By maintaining the electric field intensity within approximately 8.50-10.83 mV·cm^-1, the CH₄ yield was observed to increase by up to two-fold. The improvement in CH₄ production under optimized electric field conditions was attributed to the enhancement of the direct accepting capacity of the biocathode. This enhancement was primarily due to an increase in the relative abundance of Methanosaeta by approximately 10 % and an up to 83.78 % rise in the electron-accepting capacity of the extracellular polymeric substance. These insights offer a new perspective on the operation of methanogenic biocathodes and propose a novel biocathode construction methodology based on these findings, thus contributing to the enhancement of MEC efficiency.