Selectivity and catalytic performance of Pdx@Pty/C nanoparticles for methanol electrooxidation

Abstract

The catalytic performance of catalysts in specific oxidation reactions strongly depends on their composition and structure. In this study, we synthesized and evaluated the catalytic activity of Pdx@Pty/C core-shell nanoparticles (with x:y molar ratios of 0.2:0.8, 0.3:0.7, and 0.4:0.6) for methanol electrooxidation, aiming to investigate the influence of Pd incorporation in the core of the structure. XRD measurements revealed minor distortions in the Pt lattice parameters of all core-shell catalysts compared to Pt/C catalysts. The nanoparticles exhibited good dispersion on the carbon support, with spherical shapes and small particle sizes (3–3.5 nm). The core-shell nanoparticles are formed by a Pd-Pt-rich core and a Pt shell. Electrochemical characterizations revealed that core-shell catalysts displayed improved catalytic properties compared to Pt/C catalysts, which is due to electronic and geometric effects in the Pt structure resulting from the core-shell morphology. The Pd0.3@Pt0.7/C catalyst achieved the highest catalytic activity, presenting the lowest onset potential and the highest current densities for methanol oxidation. In situ FTIR data revealed that core-shell catalysts start CO2 production at significantly lower potentials than the Pt/C catalyst (about 500 mV lower) and achieved the highest production of this product across the potential range. Among the core-shell catalysts, Pd0.4@Pt0.6/C is the most selective material for CO2 production. These findings indicate enhanced selectivity of the catalysts, likely resulting from synergistic modifications facilitated by a higher Pd content, enabling the conversion of methanol and intermediate species on the catalyst surface.