Harnessing the synergy of metallic Ru and CoNi alloy through chemical vapor deposition: Designing ternary RuCoNi catalysts for enhanced hydrogen evolution in acidic media

Metal alloys composed of noble and transition metals are effective catalysts for accelerating the kinetics of the hydrogen evolution reaction (HER) during water electrolysis. In this study, metallic ruthenium (Ru), binary cobalt-nickel (CoNi), and ternary ruthenium-cobalt-nickel (RuCoNi) alloy thin films are fabricated on a graphite sheet substrate using a chemical vapor deposition technique to evaluate their HER performance in an acidic medium. The RuCoNi catalyst, with its interconnected faceted microstructure and strong chemical interactions between Ru and CoNi, demonstrates enhanced electronic conductivity and superior HER performance. The optimal RuCoNi alloy achieves a current density of 10 mA cm⁻² at an overpotential of 45 mV and an extraordinary current density of 1000 mA cm⁻² at 165 mV, accompanied by a low Tafel slope of 42.5 mV dec⁻¹, while maintaining consistent performance over 24 h of continuous operation. Density functional theory supports the experimental results, indicating that the ternary RuCoNi exhibits a smaller Gibbs free energy value of −0.45 eV compared to the individual Ru (−0.5 eV) and binary CoNi (−0.6 eV) catalysts, thereby supporting its enhanced HER activity. This study emphasizes the effectiveness of a simple deposition strategy for creating stable, high-performance thin-film electrocatalysts for large-scale industrial applications.