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.