Optimizing the Surface Coordination of Pd‐Cu Nanoalloy Through Chemical Ordering to Enhance Hydrogenation Selectivity

ABSTRACT Precise control of chemical ordering in bimetallic nanocatalysts offers a route to decouple activity and selectivity in acetylene hydrogenation, but direct atomic‐scale evidence linking surface order to catalytic performance is scarce. Here, we tune Pd‐Cu nanoalloys from chemically disordered to highly ordered states by composition control and targeted H 2 thermal treatment. Under near‐industrial conditions, all catalysts reach full acetylene conversion between 100°C and 120°C, whereas the ethylene selectivity enhances with the chemical ordering increasing. By combining synchrotron X‐ray absorption fine structure (XAFS) with X‐ray total scattering and reverse Monte Carlo (RMC) simulation, three‐dimensional atomic models are reconstructed to quantitatively map surface coordination. Compared with the chemically disordered Pd‐Cu nanocatalyst, the highly ordered PdCu shows an increase in average surface Pd‐Cu coordination and an expansion of mean surface Pd‐Pd separations. These structural features weaken ethylene binding and suppress re‐adsorption, rationalizing the enhanced selectivity. Our study provides direct atomic‐scale evidence connecting chemical order to catalytic selectivity and opens the way for guiding the precise design of bimetal nanocatalysts.