MoS2/NixSy/NF heterojunction catalyst for efficient oxygen evolution reaction†

The development of highly efficient and stable non-noble metal catalysts is crucial for advancing the oxygen evolution reaction (OER). In this study, a flower-branch-like MoS₂/Ni_xS_y/NF heterostructure was synthesized using a one-step hydrothermal method as an effective OER electrocatalyst. X-ray photoelectron spectroscopy (XPS) and high-resolution transmission electron microscopy (HRTEM) confirmed the formation of a heterojunction and nickel's shift to a higher oxidation state. The heterojunction enhanced electronic interactions, enriched active sites, and facilitated electron transfer, while Ni³⁺ promoted OH⁻ adsorption, boosting OER kinetics. Interfacial charge transfer from Ni_xS_y to MoS₂ activates the inert basal planes of MoS₂, enhancing intermediate adsorption. The Ni₃S₂/NiS heterointerface optimizes OER intermediate adsorption energy, significantly improving catalytic activity. This unique structure provides abundant active sites (C_dl = 75.6 mF cm⁻²), enhances charge transfer (R_ct = 2.3 Ω), and reduces the water dissociation barrier, leading to an exceptional Tafel slope of 61 mV dec⁻¹ that outperforms those of single-phase catalysts. Additionally, SO₄²⁻ leaching during the OER may aid the conversion of nickel sulfide to the NiOOH species, further improving performance. The MoS₂/Ni_xS_y/NF catalyst showed a low overpotential of 150 mV at 10 mA cm⁻², indicating excellent activity. It also demonstrated remarkable stability, with negligible decay after 50 hours under alkaline and simulated seawater conditions. This work underscores the importance and the key role of heterojunctions in enhancing electrocatalytic performance for the OER, and offers new insights for designing high-performance OER electrocatalysts.