Rational Design of Ag-Based Catalysts for the Electrochemical CO2 Reduction to CO: A Review

The selective electrochemical CO2 reduction (ECR) to CO in aqueous electrolytes has gained significant interest in recent years due to its capability to mitigate the environmental issues associated with CO2 emission and to convert renewable energy such as wind and solar power into chemical energy as well as its potential to realize the commercial use of CO2. In view of the thermodynamic stability and kinetic inertness of CO2 molecules, the exploitation of active, selective, and stable catalysts for the ECR to CO is crucial to promote the reaction efficiency. Indeed, plenty of electrocatalysts for the selective ECR to CO have been explored, of which Ag is known as the most promising electrocatalyst for large-scale ECR to CO due to several competitive advantages including high catalytic performance, low price, and rich reserves compared with other metal counterparts. To provide useful guidelines for the further development of efficient catalysts for the ECR to CO, a comprehensive summary of the recent progress of Ag-based electrocatalysts is presented in this Review. Different modification strategies of Ag-based electrocatalysts are highlighted, including exposure of crystal facets, tuning of morphology and size, introduction of support materials, alloying with other metals, and surface modification with functional groups. The reaction mechanisms involved in these different modification strategies of Ag-based electrocatalysts are also discussed. Finally, the prospects for the development of next-generation Ag-based electrocatalysts are proposed in an effort to facilitate the industrialization of ECR to CO.