Density functional theory studies of Pd and PtxPd1–x bimetallic catalysts for the H2/O2 recombination reaction

Abstract

Choosing an appropriate H2/O2 recombination catalyst is crucial for enhancing efficiency in hydrogen technologies. This study used density functional theory calculations to investigate PtxPd1–x (0 ≤ x ≤ 1) alloys with varying slab thicknesses and surface areas. The performance of these alloys and the reaction intermediates (O, H, OH, OH + H, H2O) formed on the catalyst surfaces for the H2/O2 recombination reaction was analysed. Catalytic activity of pristine Pd (111) and PtPd3, PtPd, Pt3Pd, and Pt7Pd (111) alloy surfaces was evaluated using adsorption and reaction energies. Stability was found along the (111) Miller index for all tested alloys. Strong surface adsorption was observed on PtPd (111) and PtPd3 (111) surfaces, while weaker adsorption occurred on Pt7Pd (111) surfaces. Lower activation energies were observed on Pt7Pd (111) and Pt3Pd (111) surfaces for the rate-determining step (O* + H* → *OH), compared to pristine Pd (111). In contrast, the *OH formation step was inhibited on PtPd (111) and PtPd3 (111) surfaces due to strong surface absorption of reaction intermediates. Overall, Pt3Pd (111) and Pt7Pd (111) surfaces are promising alternative catalysts for H2/O2 recombination, especially in the rate-determining *OH formation step.