Mo15S19/NiS/FeS/Nickel Foam Nanostructured Electrocatalyst for Water Electrolysis

Abstract The development of efficient and low-cost non-noble metal electrocatalysts is crucial for advancing hydrogen production via water electrolysis. Herein, a non-noble metal multi-level heterostructured bifunctional electrocatalyst, Mo15S19/NiS/FeS with typical nanosheet morphology, was in situ constructed on nickel foam (NF) via a stepwise hydrothermal method. The catalyst achieves highly efficient synergistic catalysis for the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). The multiphase architecture integrates the favorable HER characteristics of Mo15S19 with the complementary catalytic contributions of NiS and FeS toward OER, while the intimate heterointerfaces facilitate charge-transfer kinetics. The heterointerfaces enhance charge transfer and maximize the exposure of active sites. The self-supporting NF substrate endows the material with a large specific surface area and efficient mass transfer channels, avoiding activity degradation caused by powder agglomeration. The catalyst with an optimized Ni/Fe molar ratio exhibits excellent bifunctional catalytic activity in 1 M KOH. At a current density of 10 mA cm−2, the HER overpotential is only 20 mV and the OER overpotential is 200 mV, with the total cell voltage reduced to 1.49 V. It can operate continuously and stably for 200 h without significant degradation. In situ Raman spectroscopy confirmed the synergistic activation of multiple components during the catalytic process, as well as strong interfacial bonding between the active components and the NF. Furthermore, the absence of signals for sulfur oxides and metal hydroxyl oxides during the OER process demonstrates the structural stability of the catalyst, with no significant sulfur loss or profound phase transformations. This study provides a promising strategy for the high-efficiency, non-noble bifunctional electrocatalysts for sustainable hydrogen production.