Carbon Recycling through Catalysis: Direct CO2-to-CH4 Conversion as a Pathway to Sustainable Fuels

Abstract

Among the distinct value-added products of the catalyst-mediated CO2 reduction reaction (CO2RR), CH4 stands out as a superior energy carrier on account of its superior combustion heat. However, designing the highly active and selective catalytic system presents an ongoing challenge to circumvent C-C coupling that results in multi-carbon products during CO2 methanation. Consequently, substantial strategic initiatives have been pursued to enhance catalytic activity for proficient CO2 methanation, including structural modulation, catalyst composition, surface modification employing single-site catalysts, defect engineering, cocatalysts, elemental doping, optimising operating conditions, and so on. This present review addresses diverse perceptions and strategies regarding thermocatalytic, electrocatalytic, and photocatalytic hydrogenation of CO2 to CH4, utilizing renewable energy sources as embraced by the scientific fraternity from onset to cutting-edge progress. Furthermore, this review highlights the catalytic mechanisms, kinetics, and the roles of active components, supports, and promoters for CO2 methanation. In addition, the feasibility and economic potential of compressed natural gas (CNG) production through CO2 methanation are critically examined, emphasizing its cost-effectiveness and scalability for large-scale implementation. Finally, this review ruminates on a comprehensive roadmap for advancing catalyst design and optimizing processes to enable economically sustainable CNG production.