Highly Selective Electroreduction of CO2 to CH4 on Cu–Pd Alloy Catalyst: the Role of Palladium‐Adsorbed Hydrogen Species and Blocking Effect

Electroreduction of CO2 to chemical fuels offers a promising strategy for controlling the global carbon balance and addressing the need for the storage of intermittent renewable energy. In this work, it is demonstrated that tuning adjacent active sites enables the selection of different reaction pathways for generating C1 or C2 products during the electroreduction of CO2. Cu and Cu-Pd alloy catalysts with different atomic ratios are synthesized and investigated to elucidate their different electroreduction selectivities for CO2 electroreduction. Cu catalyst favors the formation of C2 products since the neighboring active Cu sites are beneficial for coupling adjacently adsorbed *CO and *CHO intermediates. Cu alloyed with Pd introduces a blocking effect and increases the intermolecular distance between adjacent adsorbed *CO and *CHO intermediates. Therefore the selectivity for the C2H4 pathway decreas while the CH4 pathway is enhanced. Moreover, the existence of adsorbed *H species on Pd atoms also played a significant role in boosting CO2 electroreduction to CH4 by facilitating the hydrogenation of *CO intermediates. This work reveals the key role of *H species adsorbed on Pd atoms and the blocking effect between active sites for CH4 formation, which is helpful for the design of copper-based catalysts for desired products.