Electrochemical CO 2 reduction on noble metals: parameters, performance, and practical pathways

The electro-chemical CO2 reduction reaction (ECO2RR) coupled with renewable energy, is regarded as a promising approach to fulfil the carbon neutralisation by transforming the CO2 into high-value-added chemicals and fuels. Considerable progress has been attained in the last decade in the creation of membranes, engineering of the electrodes, identification of new potential electrocatalysts, and highly efficient electrolyzers. Carbon monoxide (CO) production via this route is less energy intensive considering its potentially renewable energy-driven production and ease of product separation. Given the wide usage of CO, this review focuses on the recent progress in ECO2RR to CO employing noble metal–base electrocatalysts in different electrochemical cells, focusing on zero-gap electrolyzers. The morphology-tuned electrocatalysts exhibited better activity, which might be due to higher corners and edges available for the reaction. The issues and challenges linked to the gas diffusion electrode (GDE) and the way forward to eliminate them have been presented. It is also noted that the flow channel, electrolyte, and gas flow rate significantly affect the activity and selectivity of the CO2 electrolyzer. In the final analysis, a few remarks about photo-electrocatalysis are mentioned such as a solar cum electrolysis process integration that might be a good alternative from a sustainability perspective.