Microbial electrosynthesis of CO₂ to multiple carbon products: Metabolic pathways, key factors, and sustainable prospects

In recent years, CO₂ emission has been a global consensus that it is urgent to reduce CO₂ emissions and realize CO₂ resource utilization. However, current technologies for CO₂ reduction have the problems of high energy input, high operational costs, and a risk of secondary pollution. Microbial electrosynthesis (MES) combines the metabolic activities of microorganisms on electrodes with electrical energy to convert CO₂ into organics. Although MES has the advantages of mild reaction conditions, low operational cost, and potential for high-value-added products, it still confronts obstacles like low electron transfer efficiency, low conversion rate, improper reactor design and operation, etc. Therefore, this paper provided a comprehensive review of MES with CO₂ conversion, aiming to identify the determinants of the process and exploit its future research directions. There are three tasks in this review: Firstly, typical fatty acid and alcohol production (3.5 to 5700 mg L⁻¹ d⁻¹) from MES and their metabolic pathways were introduced elaborately. Secondly, the determining factors of MES, such as reactor configuration, electrode material, cathodic potential (generally −0.8 to −1.2 V vs. Ag/AgCl), and coulombic efficiency (17.6 % to 113.6 %), were comprehensively discussed. Finally, challenges of microbial electrochemical reduction of CO₂ were discussed, and future research directions were proposed.