Ru Nanocluster-Anchored CoMoO_4–<i>x</i> Nanoflowers for Efficient Hydrogen Evolution Reaction

Designing an affordable catalyst for the hydrogen evolution reaction (HER) in alkaline media remains a major challenge. In this study, we synthesized a Ru-CoMoO4–x/NF catalyst modified with ruthenium nanoclusters (Ru NCs) and oxygen vacancies (Ovs), using nickel foam (NF) as the substrate. X-ray photoelectron spectroscopy (XPS) analysis showed that introducing Ru nanoclusters effectively modified the catalyst’s electronic structure. A carefully controlled concentration of oxygen vacancies enhanced the catalyst’s stability, reduced electrochemical impedance, and promoted hydrogen evolution kinetics, thereby improving the intrinsic activity of Ru-CoMoO4–x/NF. In an alkaline freshwater medium, Ru-CoMoO4–x/NF displayed a low overpotential of 20 mV to achieve a current density of −10 mA cm–2, with a Tafel slope of 41.54 mV dec–1. The catalyst maintained stable performance with minimal degradation after 100 h in constant voltage tests and 180 h in multistep constant current tests. Moreover, in an overall water-splitting system, Ru-CoMoO4–x/NF∥Ru-CoMoO4–x/NF required only 1.606 V to drive −50 mA cm–2. This work presents a viable approach to enhancing the HER electrocatalytic performance of nonprecious metal oxides through the synergistic effects of Ru NCs and Ovs.