Progress in tracking electrochemical CO2 reduction intermediates over single-atom catalysts using operando ATR-SEIRAS

Owing to the multiple proton-coupled electron transfer steps involved in the electrochemical carbon dioxide reduction reaction (CO₂RR), single-atom catalysts (SACs) are ideal platforms for studying such complex chemical reaction processes. The structural simplicity and homogeneity of SACs facilitate the understanding of the structure-performance relationship and reaction mechanisms of the CO₂RR. Operando attenuated total reflection surface-enhanced infrared absorption spectroscopy (ATR-SEIRAS) is a valuable tool to identify the dynamic intermediate transformation processes in the CO₂RR occurring on SACs and to study the impact of local reaction environments on the CO₂RR performance. This article reviews operando ATR-SEIRAS and its key applications in the SAC-catalyzed CO₂RR. The review briefly introduces the surface enhancement mechanism of electrochemical in situ infrared spectroscopy, formation mechanisms of the C1 and C2 products, function of operando ATR-SEIRAS in investigating the mechanisms of single-/dual-atom catalysts in converting CO₂/CO to C1 and C2 products, and methods of using spectroscopic information to determine the interfacial H₂O and local pH at the electrode. Finally, the review provides perspectives on the future development of operando ATR-SEIRAS.