Interfacial Electric Field-Mediated Stabilization of Unsaturated RuO2–x Clusters on MoO3–Ni(OH)2 Heterostructure for Enhanced pH-Universal Hydrogen Evolution

Ru-based clusters represent a class of promising electrocatalysts for pH-universal hydrogen evolution reaction (HER), yet their practical application is hindered by nanoparticle aggregation and strong oxygen affinity, leading to compromising activity and stability. This study proposes a strategy by integrating strong metal–support interactions with a built-in electric field (BIEF), in which the electrostatic interaction facilitates the design of a class of heterostructure catalysts comprising RuO2–x clusters and MoO3 on Ni(OH)2 (RuO2–x/MoO3–Ni(OH)2). Detailed characterizations reveal that the engineered BIEF induces charge redistribution, leading to the enhanced electron density at Ru active sites. This electronic modulation effectively weakens the adsorption of the OH group while substantially boosting catalytic activity and stability. The synthesized RuO2–x/MoO3–Ni(OH)2 achieves low overpotentials of 64, 150, and 83 mV at 100 mA cm–2 in 1.0 M KOH, 1.0 M phosphate-buffered saline (PBS), and 0.5 M H2SO4, respectively. Furthermore, it exhibits robust stability for 150 h at 100 mA cm–2 in an alkaline solution. In an anion exchange membrane water electrolyzer, the catalyst requires only 1.76 V to attain 0.5 A cm–2. This work establishes a pioneering pathway for designing efficient electrocatalysts toward the production of clean energy carriers.