Ultra-low iridium-doped NiMo-based sulfides nanoflowers on nickel foam: an effective catalyst for oxygen evolution...

The development of high-performance bifunctional electrocatalysts is crucial for advancing sustainable energy conversion. In the present work, a transition metal sulfide catalyst with excellent activities toward the oxygen evolution reaction (OER) as well as the urea oxidation reaction (UOR) activities was successfully designed by constructing Ir@Ni₃S₂/MoS₂/NF crystalline/amorphous heterostructures. The material demonstrates outstanding electrocatalytic performance: current densities of 10 and 100 mA cm^-2 are realized in the OER process at overpotentials of only 188.6 and 260.9 mV, respectively, while maintaining stability for a duration of 210 h. In the UOR process, current densities of 10 and 100 mA cm^-2 are accomplished at potentials of merely 1.27 V and 1.32 V, respectively, with no deterioration in performance observed over 50 h. This remarkable catalytic behavior stems from the synergistic effect among the metal elements, which significantly accelerates electron transfer and enhances reaction kinetics. Iridium (Ir) doping successfully tailors the electronic structure of the Ni₃S₂/MoS₂ heterojunction, as revealed by density functional theory (DFT) calculations. The incorporation of Ir not only optimizes the adsorption behavior of key oxygen-containing intermediates but also significantly reduces the reaction energy barrier, leading to enhanced OER activity. Additionally, Ir doping creates crystalline/amorphous interfaces rich in unsaturated coordination sites, working synergistically to enhance reactant adsorption. This investigation supplies fundamental understandings of the scheme of bimetallic sulfide-derived catalysts with trace noble metal doping for sustainable hydrogen production.