An Efficient Bifunctional Ru/RuO 2 Heterojunction Catalyst for Acidic Overall Water Splitting

ABSTRACT A bifunctional Ru/RuO 2 heterojunction catalyst (Ru/RuO 2 ‐0.5) was constructed by a calcination‐reduction for acidic overall water splitting. Interface engineering induces directional electron transfer across Ru/RuO 2 heterointerfaces, optimizing the electronic structure of active sites. Exceptional bifunctional catalytic capability is exhibited by the as‐prepared catalyst within 0.5 M H 2 SO 4 acidic media. To achieve a current density of 10 mA cm −2 , the hydrogen evolution reaction (HER) demands an ultralow overpotential of 60.4 mV, while the oxygen evolution reaction (OER) requires only 165 mV., with excellent stability over 24 h. In a two‐electrode electrolyzer, achieves 10 mA cm −2 with a cell voltage of only1.48 V, surpassing the commercial Pt/C‖RuO 2 benchmark (1.61 V). This work holds significant implications for the advancement of green hydrogen production technologies.