A review on electrochemical conversion of CO2 to CO: Ag-based electrocatalyst and cell configuration for industrial application

The current review discusses the recent advances in Ag-based electrocatalysts for electrocatalytic conversion of CO2 to CO. The comparable electrocatalytic activity, stability, and lower cost of the Ag-based catalysts with that of Au- and Pd-based catalysts make the former commercially more viable for the electrochemical CO2 conversion to CO. The challenges associated with the electrochemical CO production are discussed. The impacts of the surface composition, surface area, particle size, porosity, lattice edge, crystal plane, and the defects on the catalytic activity of the electrocatalyst are also reviewed. CO2 electrolysers, especially the membrane electrode assembly (MEA)-based electrolyser and its constituents, are described. The infrastructure of the gas diffusion electrode (GDE) and development thereof was found critical for the microenvironment of the liquid–gas interface near the catalyst surface in a GDE-based system to sustain a higher activity over a period of time still remains a challenge. Hence, pathways to cautiously produce benchmark GDEs are discoursed. The role of different ion-exchange membranes and the associated challenges are reviewed. In the end, perspectives on catalyst design and the electrochemical CO2 reduction (eCO2R) to CO process are given to assist in further improving the electrocatalytic efficiency.