Synergistic Interfacial Effect of Ru/Co3O4 Heterojunctions for Boosting Overall Water Splitting

Abstract Low‐cost bifunctional electrocatalysts capable of efficiently driving the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) are needed for the growth of a green hydrogen economy. Herein, a Ru/Co 3 O 4 heterojunction catalyst rich in oxygen vacancies (V O ) and supported on carbon cloth (RCO‐V O @CC) is prepared via a solid phase reaction (SPR) strategy. A RuO 2 /Co 9 S 8 @CC precursor (ROC@CC) is first prepared by loading Co 9 S 8 nanosheets onto CC, following the addition of RuO 2 nanoparticles (NPs). After the SPR process in an Ar atmosphere, Ru/Co 3 O 4 heterojunctions with abundant V O are formed on the CC. The compositionally optimized RCO‐V O @CC electrocatalyst with a Ru content of 0.55 wt.% exhibits very low overpotential values of 11 and 253 mV at 10 mA cm −2 for HER and OER, respectively, in 1 m KOH. Further, a low cell voltage of only 1.49 V is required to achieve a current density of 10 mA cm −2 . Density functional theoretical calculations verify that the outstanding bifunctional electrocatalytic performance originates from synergistic charge transfer between Ru metal and V O ‐rich Co 3 O 4 . This work reports a novel approach toward a high‐efficiency HER/OER electrocatalyst for energy storage and conversion.