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

• The H 2 /O 2 recombination activity of Pt 3 Pd , PtPd, Pt 7 Pd , and PtPd 3 alloys is not well understood, prompting this study. • The study examined surface stability, reaction intermediates, and catalytic activity of Pd-Pt alloys' dominant surface facet. • O* + H* → OH* is more favourable on Pd, Pt 3 Pd, and Pt 7 Pd (111) surfaces than Pt (111), but slightly less active for H 2 O* formation. • Gibbs free energy shows *OH formation is the rate-determining step; Pt 3 Pd and Pt 7 Pd (111) perform best for H 2 /O 2 recombination. Choosing an appropriate H 2 /O 2 recombination catalyst is crucial for enhancing efficiency in hydrogen technologies. This study used density functional theory calculations to investigate Pt x Pd 1–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, H 2 O) formed on the catalyst surfaces for the H 2 /O 2 recombination reaction was analysed. Catalytic activity of pristine Pd (111) and PtPd 3 , PtPd, Pt 3 Pd, and Pt 7 Pd (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 PtPd 3 (111) surfaces, while weaker adsorption occurred on Pt 7 Pd (111) surfaces. Lower activation energies were observed on Pt 7 Pd (111) and Pt 3 Pd (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 PtPd 3 (111) surfaces due to strong surface absorption of reaction intermediates. Overall, Pt 3 Pd (111) and Pt 7 Pd (111) surfaces are promising alternative catalysts for H 2 /O 2 recombination, especially in the rate-determining *OH formation step.