MOF-Derived CoS₂@NiS-MoS₂ Ternary Composite Heterojunction Electrocatalyst for Efficient Water Splitting

Abstract

Finding efficient, stable, and inexpensive electrocatalysts is the key for water-splitting for developing hydrogen energy technology. The abundant MoS2 has hydrogen evolution activity comparable to that of Pt and is regarded as an efficient alternative for noble-metal-based electrocatalysts; however, it cannot be widely used due to the limitation of less exposed active sites. Herein, we propose a metal–organic framework (MOF)-etching and vulcanization strategy to design CoS2@NiS-MoS2 ternary composite heterostructures on Ti foil. The MOF-derived open framework structure is conducive to electrolyte entry and bubble diffusion, and a large number of nanosheet edges are exposed to greatly increase the number of active sites. Moreover, the heterojunction heterogeneous interface formed by CoS2, NiS, and MoS2 adjusts the local charge distribution and reduces the kinetic barrier during water splitting. In 1 mol/L KOH, the electrocatalyst required only 91 mV overpotential to deliver a current density of 10 mA cm–2 and had a Tafel slope of 53 mV dec–1 and good electrochemical stability. This work highlights the importance of control strategies for surface engineering at multiple scales, which can be used for the exploration of efficient and robust electrocatalysts for large-scale alkaline electrolyzers.