Toward the Sabatier Principle‐Guided Design of Low‐Platinum‐Group‐Metal Trimetallic Nanocatalysts for Efficient Hydrogen Evolution and Oxidation Reactions

Abstract The rational design of medium‐entropy low‐platinum‐group‐metal (PGM) trimetallic nanocatalysts for both hydrogen evolution (HER) and hydrogen oxidation reactions (HOR) is reported, guided by the Sabatier principle. By alloying a PGM (Ir, Pt, Pd, Ru, or Rh) with Mo, which strongly binds hydrogen (H*) and hydroxyl (OH*) intermediates, and Cu, which exhibits a weaker binding affinity, catalysts with tunable adsorption properties are developed. An autocatalytic reduction‐mediated synthesis is established, in which PGM atoms facilitate the reduction of more challenging Mo(V) and Cu(II) species at temperatures below 300 °C, as evidenced by hydrogen temperature‐programmed reduction and high‐resolution powder X‐ray diffraction analyses. Crystallization analysis and synchrotron X‐ray absorption spectroscopy (XAS) reveal that Ir‐Mo‐Cu nanocatalysts form an atomically mixed single‐phase, in contrast to the other four PGM‐Mo‐Cu nanocatalysts with poor crystallinity or phase separation. Among them, Ir‐Mo‐Cu nanocatalysts achieve an exceptional HER mass activity, nearly seven times higher than commercial Pt/C, and exhibit excellent HOR mass activity with outstanding durability. Furthermore, density functional theory calculations and operando XAS reveal that the mixing of Ir with Mo and Cu effectively tunes the adsorption strengths of H* and OH*, achieving a balanced interaction that enhances catalytic performance while keeping the noble metal content below 20 at.%.