Band filling mediated D-band center shift in palladium hydride to improve hydrogen evolution electrocatalysis

While hydrogen serves as a pivotal energy carrier for the global clean energy transition, its sustainable production hinges on the strategic design of electrocatalysts that can maximize noble-metal efficiency to overcome current cost and performance barriers. Here, the synergistic integration of the FeNi-C support effect and hydrogen insertion in PdH x significantly enhances acidic HER performance, achieving a low overpotential of 40.8 mV at −10 mA cm −2 and a J 0,geo of 0.774 mA cm −2 (32% higher than commercial Pt/C). This synergy is driven by a consistent electronic redistribution: Bader charge analysis reveals the NC shell reservoir captures −5.66 e from the depleted FeNi core (+5.88 e) to mediate a −0.22 e gain at the PdH x surface. In parallel, XPS analysis during the Pd/FeNi-C to PdH x /FeNi-C transition confirms metallic depletion (Fe 0 : 41.1% → 13.4%; Ni 0 : 19.0% → 11.0%) and hydride enrichment (Pd-H: 33.1% → 53.9%). Furthermore, XAS the adsorption edge energy (E 0 ) shifts confirm a stepwise electronic evolution from the baseline (FeNi-C/Pd-foil) through the intermediate Pd/FeNi-C to final PdH x /FeNi-C, verifying progressive core oxidation (Fe: 7115.7 → 7117.5 → 7117.7 eV; Ni: 8336 → 8337.5 → 8340.2 eV) and surface reduction (Pd: 24350 → 24,349.7 → 24,349.2 eV). Collectively, these modulations downshift the Pd d-band center to −2.51 eV, which, coupled with a ~3.5-fold higher ECSA (89.3 cm 2 for PdH x /FeNi-C vs. 25.6 cm 2 for PdH x /C) and reduced R ct (18.81 Ω for PdH x /FeNi-C vs. 40.21 Ω for PdH x /C), establishes a robust framework for high-performance noble-metal electrocatalysts. • Remote band-filling through a FeNi-C core-shell support allows precise control of the Pd electronic state via an active electron-donation pathway • The synergy between FeNi-C-mediated band filling and interstitial hydrogen insertion lowers the Pd d-band center to –2.51 eV, enhancing hydrogen adsorption and desorption kinetics • PdHx/FeNi-C demonstrates excellent acidic HER performance with a low overpotential of 40.8 mV at –10 mA cm -2 in 0.5 M H 2 SO 4 , exceeding the commercial 20% Pt/C benchmark • PdH x /FeNi-C delivers a high geometric exchange current density (J 0,geo ) of 0.774 mA cm -2 , which is approximately 32% higher than that of commercial Pt/C