Fine-tuning of Pd-Rh core-shell catalysts by interstitial hydrogen doping for enhanced methanol oxidation

Metal catalysts play an important role in the catalytic electrochemical processes and optimization of their performance is usually achieved through alloying with other metal atoms. Doping with interstitial hydrogen atoms is a special but effective way to regulate the electronic structure of host catalysts. Herein we demonstrate the intermixing of Pd and Rh atoms during the hydrogen-doping process of Pd@Rh core-shell nanocubes, forming an alloyed surface in Pd@Rh-H. The catalysts show enhanced performance in electrocatalytic methanol oxidation, as compared to commercial Pt/C and are even better than PdH@Rh core-shell nanocubes. The small structural differences between the two hydride catalysts are revealed by X-ray electron spectroscopy and pair distribution function analysis of electron diffraction. The theoretical calculation results show that Rh in Pd@Rh-H contains more negative charges than Rh in PdH@Rh, indicating more effective charge transfer in Pd@Rh-H. The d-band center (ε_d) of the Rh site in Pd@Rh-H shifts up, and the synergy between Rh and Pd optimizes the binding energy of CO and OH, inducing preferential catalytic activity. Our work provides guidance for the synthesis of high-performance catalysts by doping with interstitial atoms, which may provide a new strategy to fine-tune the electronic structure of other bimetallic nanoparticles.