d‐Band Optimized Hydrogen Adsorption and Dynamic Reconstruction‐Accelerated Oxygen Evolution on RuS ₂ /(FeNi)S _1.03 Heterointerfaces for Water/Seawater Splitting

Abstract Designing efficient bifunctional electrocatalysts for the kinetically divergent hydrogen and oxygen evolution reactions (HER/OER) is challenging due to their conflicting interfacial requirements. Herein, precisely engineered RuS ₂ /(FeNi)S _1.03 heterointerfaces are constructed via homogeneous chelation‐coupled in situ sulfidation, enabling distinct interfacial mechanisms that independently enhance HER and OER. For HER, the RuS ₂ component exclusively optimizes HER through static electronic modulation, where interfacial electron transfer at RuS ₂ /(FeNi)S _1.03 interface downshifts the Ru d‐band center to −1.99 eV and weakens hydrogen adsorption ( 0.51 eV). This yields superior HER activity with an overpotential of 270 mV@ at 50 mA cm ⁻² . Conversely, for OER, the (FeNi)S _1.03 phase undergoes dynamic reconstruction, transforming into an OER‐catalytically active Fe‐NiO oxide with stable RuS ₂ (RuS ₂ /Fe‐NiO interfaces) that reduce intermediate energy barriers and delivers an overpotential of 300 mV at 50 mA cm ⁻² . This dual‐interface synergy enables outstanding bifunctional performance with low cell voltages (1.68 V alkaline water; 1.76 V seawater) and industrial stability (>250 h at 1000 mA cm ^{− 2} ), resolving the mechanistic conflict in bifunctional catalyst design.