Crowding-Out Effect in Synergistic C–C Coupling on PdNi Alloy Nanoparticles Studied by Surface-Enhanced Raman Spectroscopy

The advancement of catalysis has been significantly propelled by the evolution of bimetallic nanocatalysts from their monometallic analogues. Nevertheless, the fundamental understanding of why bimetallic nanocatalysts exhibit superior or distinct performances compared with the corresponding monometallic counterparts remains elusive. In this study, we implement a palladium–nickel (PdNi) bimetallic nanoparticle-catalyzed Sonogashira cross-coupling reaction as a research model, which is a vital reaction for forming carbon–carbon bonds in organic synthesis. By using surface-enhanced Raman spectroscopy (SERS), we find that the exceptional performance of bimetallic nanocatalysts observed in the PdNi-catalyzed reaction results from the positive crowding-out effect of active Pd species. Furthermore, the study shows that the effect is regulated by the doping of Ni, which is also demonstrated by X-ray photoelectron spectroscopy (XPS) results and density functional theory (DFT) calculations. This study enlightens the intricate synergistic mechanism that governs bimetallic catalysis and hence provides a new understanding on the superior performance of bimetallic catalysts over monometallic catalysts.