Local-strain-induced CO adsorption geometries and electrochemical reduction pathway shift.

Unravelling the influence of strain and geometric effects on the electrochemical reduction of carbon dioxide (CORR) on Cu-based (or Pd-based) alloys remains challenging due to complex local microenvironment variables. Herein, we employ two PdCu alloys (nanoparticles and nanodendrites) to demonstrate how CORR selectivity can shift from CO to HCOO. Despite sharing consistent phases, exposed crystal facets, and overall oxidative states, these alloys exhibit different local strain profiles due to their distinct geometries. By integrating experimental data, spectroscopy, and density functional theory calculations, we revealed that CO prefers adsorption on tensile-strained areas with carbon-side geometry, following a *COOH-to-CO pathway. Conversely, on some compressive-strained regions induced by the dendrite-like morphology, CO adopts an oxygen-side geometry, favoring an *OCHO-to-HCOO pathway due to the downshift of the -band center. Notably, our findings elucidate a dominant *OCHO-to-HCOO pathway in catalysts when featuring both adsorption geometries. This research provides a comprehensive model for local environment of bimetallic alloys, and establishes a clear relationship between the CORR pathway shift and variation in local strain environments of PdCu alloys.