Synthesis of isolated Ru–O₃ sites on hexagonal close-packed intermetallic penta-metallene for hydrogen oxidation electrocatalysis

Atomically thin two-dimensional alloys are interesting for electrocatalysis but suffer from poor functional robustness and wide active-site heterogeneity. Here the synthesis of an unconventional hexagonal close-packed-phase intermetallic Pd-based multi-metallene, on which isolated Ru–O₃ atomic sites are homogeneously dispersed, overcomes these obstacles. This structure exhibits excellent hydrogen oxidation reaction (HOR) activity, durability and anti-CO poisoning performance. The mass activity and exchange current density reach 11.5 mA μg⁻¹ and 1.0 mA cm⁻², respectively, showing some of the fastest reaction kinetics reported for Pd-based HOR catalysts. In situ Raman spectroscopy and theoretical investigations confirm that the intensified ligand effect derived from orderly atomic arrangement tends to strengthen the adsorption of hydroxyl and water, while the homogeneous Ru–O₃ sites contribute to weakened binding of HOR-involved intermediates (^*H, ^*OH and ^*H₂O), leading to a favourable reaction pathway. This work demonstrates the importance of high-valence Ru and surface O species in enhancing the synergetic process and water reorganization. (Figure presented.).