An interactive study of catalyst and mechanism for electrochemical CO2 reduction to formate on Pd surfaces

Electrochemical CO2 reduction reaction to formate (CO2RRTF) on Pd-based surfaces merits very low overpotentials, yet is challenged with identification of a high-performance catalyst and validation of the reaction pathway. In this work, an interactive study of catalyst and mechanism is presented to address the above bottleneck. On one hand, inspired by preliminary mechanistic understanding of HCOOH <-> CO2 interconversion at Pd surfaces, a Bi-modified Pd/C with the known high performance towards formic acid dehydrogenation (FAD) is elected as the prototype candidate catalyst for CO2RRTF, exhibiting indeed significantly higher activity, selectivity, durability and extended working potentials. On the other hand, the CO2 chemical hydrogenation mechanism is clarified with monodentate formate being the key intermediate for CO2RRTF on Pd surfaces, by applying isotope labeled ATR-SEIRAS measurement and kinetic analysis in conjunction with DFT calculations. The research paradigm facilitates locating efficient catalysts and advancing mechanistic study for CO2RRTF on Pd surfaces and beyond.