Tuning Reaction Pathways of Electrochemical Conversion of CO₂ by Growing Pd Shells on Ag Nanocubes

The electrochemical carbon dioxide reduction reaction (CO₂RR) has been studied on Ag, Pd, Ag@Pd_1-2L nanocubes using a combination of in situ characterization and density functional theory calculations. By manipulating the deposition and diffusion rates of Pd atoms on Ag nanocubes, Ag@Pd core-shell nanocubes with a shell thickness of 1-2 atomic layers have been successfully synthesized for CO₂RR. Pd nanocubes produce CO with high selectivity due to the transformation of Pd to Pd hydride (PdH) during CO₂RR. In contrast, PdH formation becomes more difficult in Ag@Pd_1-2L core-shell nanocubes, which inhibits CO production from the *HOCO intermediate and thus tunes the reaction pathway toward HCOOH. Ag nanocubes exhibit high selectivity toward H₂, and there is no phase transition during CO₂RR. The results demonstrate that the CO₂RR reaction pathways can be manipulated through engineering the surface structure of Pd-based catalysts by allowing or preventing the formation of PdH.