Bifunctional Electrocatalyst Enhanced Synergistically by MoS2/Ni3S2 Heterojunctions and Au Nanoparticles for Large-Current-Density Overall Water Splitting

Developing transition metal based overall water splitting (OWS) electrocatalysts with high efficiency, low-cost, large current density, and long-term stability is crucial for industrial electrolysis of water, but remains a major challenge. In this study, a hierarchical electrocatalyst with MoS₂/Ni₃S₂ heterojunctions and a tiny amount of Au nanoparticles grown on nickel foam (MoS₂/Ni₃S₂-Au@NF) has been developed by a one-step hydrothermal method. The heterojunctions and Au nanoparticle decoration induce the electron-rich interfaces in the catalyst, which facilitate the synergistic adsorption of both OER and HER intermediates. As a result, MoS₂/Ni₃S₂-Au@NF possesses an excellent bifunctional electrocatalytic performance in 1 M KOH with low HER overpotential (78 mV@10 mA cm⁻², 253 mV@500 mA cm⁻²), low OER overpotential (261 mV@50 mA cm⁻², 435 mV@500 mA cm⁻²), and outstanding cyclical stability and continuous stability, which are superior than typical benchmarks of Pt/C and RuO₂. An electrolyzer assembled with the self-supported MoS₂/Ni₃S₂-Au@NF electrode also displays excellent OWS activity and stability with a current density beyond 100 mA cm⁻². This experiment is responding a potential alternative non-precious metal electrocatalyst for OWS at industrial settings, and thus promotes the real-world application of hydrogen energy conversions.