High-entropy alloys with stable grain boundaries by Pt/Ru atomic site occupation

High-entropy alloys hold immense promise for electrocatalytic water splitting, while they may be accompanied by irreversible dissolution of noble metals during operation, limiting their practical application. In this study, a stable grain boundary face-centered cubic FeCoNiPtRu high-entropy alloy was fabricated by ultrafast carbon thermal shock to synchronously reduce multi-metal precursors. The ultra-fast reversion to high temperature of 1000 °C within 55 ms endowed the high-entropy alloy with a uniform distribution of metal elements, while the stable grain boundaries were formed at the alloy edges during the rapid cooling process at a rate of 10 °C/ms. Notably, the high-entropy alloy possessed a unique nano-confined atomic structure, with EXAFS revealing elongated Pt Pt bonds (2.88 Å) and shortened Ru Ru bonds (2.42 Å), indicative of partial Ru oxidation. DFT calculations suggest that a configuration with Pt at face-centered sites and Ru at corner sites is consistent with these bond length trends and yields a narrowed pseudo-gap and downshifted d-band center. This specific atomic arrangement could enable Pt corner sites to electronically stabilize neighboring Ru atoms, thereby enhancing charge transfer kinetics and oxidation resistance. This enhanced both charge transfer kinetics and oxidation resistance, enabling the catalyst to retain 87% of its initial current density after 25 h of high-current operation at 350 mA cm −2 . The optimized catalyst delivered low overpotentials of 48 mV (hydrogen evolution reaction) and 222 mV (oxygen evolution reaction) at 10 mA cm −2 in 1.0 M KOH, outperforming commercial Pt/C (94 mV) and RuO₂ (547 mV). This research highlighted lattice site engineering as a notable paradigm for designing anti-dissolution multi-metal electrocatalysts for water electrolysis.