Multiheterostructure Electrocatalyst Engineered by In Situ Growth of NiS 2 /ReS 2 Interface on 2D MOF‐Derived CoS 2 Nanoarrays for Enhanced Electrocatalytic Water Splitting

Developing bifunctional electrocatalysts in alkaline water splitting remains a significant challenge for hydrogen production. Herein, a novel hierarchical electrocatalyst by coupling rhenium disulfide/nickel sulfide heterostructure with the two‐dimensional metal‐organic framework‐derived CoS 2 nanoarrays (CoS 2 @ReNiS) is designed. The hierarchical structure provides abundant active sites, and heterogeneous interfaces can facilitate electron transfer. The surface electronic structure is optimized by coupling multiple metal sulfides, and the interfacial interaction is favorable to enhancing catalytic activity. As confirmed by microscopic and spectroscopic analysis, the interfacial engineering between multiple metal sulfides creates defect‐rich active sites and modulates local electronic environment to enhance catalytic activity, and the boosted catalytic activity and catalytic mechanism are elucidated by the theoretical calculation. Only 85 and 256 mV of overpotential are required for CoS 2 @ReNiS during the hydrogen and oxygen evolution reactions in alkaline electrolytes at 10 mA cm −2 . Small Tafel slopes and low charge transfer resistance display the rapid reaction kinetics. For the symmetric CoS 2 @ReNiS || CoS 2 @ReNiS electrolyzer, the voltage is only 1.57 V at 10 mA cm −2 , maintaining outstanding catalytic stability for 24 h. This work demonstrates an effectiveness of multicomponent heterostructure design and interface engineering strategies for developing advanced bifunctional electrocatalysts for water splitting.