Electro-conversion of carbon dioxide (CO₂) to low-carbon methane by bioelectromethanogenesis process in microbial electrolysis cells: The current status and future perspective

Given the aggravated greenhouse effect caused by CO₂ and the current energy shortage, CO₂ capture and reuse has been gaining ever-increasing concerns. Microbial Electrolysis Cells (MECs) has been considered to be a promising alternative to recycle CO₂ bioelectrochemically to low-carbon electrofuels such as CH₄ by combining electroactive microorganisms with electrochemical stimulation, enabling both CO₂ fixation and energy recovery. In spite of the numerous efforts dedicated in this field in recent years, there are still many problems that hinder CO₂ bioelectroconversion technique from the scaling-up and potential industrialization. This review comprehensively summarized the working principles, extracellular electron transfers behaviors, and the critical factors limiting the wide-spread utilization of CO₂ electromethanogenesis. Various characterization and electrochemical testing methods for helping to uncover the underlying mechanisms in CO₂ electromethanogenesis have been introduced. In addition, future research needs for pushing forward the development of MECs technology in real-world CO₂ fixation and recycling were elaborated.