In Situ Raman Spectroscopic Studies of Electrochemical CO2 Reduction on Cu-Based Electrodes

The electrochemical CO2 reduction reaction (CO2RR), which utilizes renewable energy to produce carbon-neutral chemicals and fuels, offers a potential pathway toward achieving global carbon neutrality. Cu-based catalysts have gained significant attention in this field due to their unique coupling ability to convert CO2 into multicarbon products, while maintaining high Faradaic efficiency. However, the CO2RR process is complex, involving a multistep proton–electron transfer process that involves intermediates associated with carbon- and oxygen-containing species. Therefore, this work aims to review the recent progress of in situ surface-enhanced Raman spectroscopic (SERS) studies of CO2RR on Cu-based catalysts. The possible reaction mechanism of CO2RR has been first discussed. In situ SERS studies of CO2RR on Cu-based single-crystal electrodes and nanocatalysts with different electronic states, morphologies, and compositions have been reviewed, and various intermediates during CO2RR have been captured to clarify the reaction mechanisms and structure–activity relationships. Moreover, the future opportunities and challenges for CO2RR electrocatalysis are presented. This review will provide fundamental insights for the understanding of CO2RR mechanisms and the design of more efficient, selective, and stable CO2RR catalysts.