Progress in inorganic cathode catalysts for electrochemical conversion of carbon dioxide into formate or formic acid

As a greenhouse gas, carbon dioxide in the atmosphere is one of the key contributors to climate change. Many strategies have been proposed to address this issue, such as CO2 capture and sequestration (CCS) and CO2 utilization (CCU). Electroreduction of CO2 into useful fuels is proving to be a promising technology as it not only consumes CO2 but can also store the redundant electrical energy generated from renewable energy sources (e.g., solar, wind, geothermal, wave, etc.) as chemical energy in the produced chemicals. Among all of products from CO2 electroconversion, formic acid is one of the highest value-added chemicals, which is economically feasible for large-scale applications. This paper summarizes the work on inorganic cathode catalysts for the electrochemical reduction of CO2 to formic acid or formate. The reported metal and oxide cathode catalysts are discussed in detail according to their performance including current density, Faradaic efficiency, and working potentials. In addition, the effects of electrolyte, temperature, and pressure are also analyzed. The electroreduction of CO2 to formic acid or formate is still at an early stage with several key challenges that need to be addressed before commercialization. The major challenges and the future directions for developing new electrocatalysts for the reduction of CO2 to formic acid are discussed in this review.