Structural and Phase Engineering of a Hierarchical 2D–2D Nickel MOF/Hydroxide‐Derived Ni0.85Se/NiTe2 Heterointerface for Robust HER, OER, and Overall Water Splitting

Abstract The development of a nonnoble metal‐based cost‐effective, efficient, and durable bifunctional electrocatalyst is crucial to achieving the goal of carbon neutrality. In this study, a structural and interfacial engineering approach is employed to design a 2D–2D hierarchical nickel MOF/nickel hydroxide‐derived nickel selenide/nickel telluride dual‐phase material through a single‐step selenotellurization process. The rational design of highly ordered nanoarchitectures provides well‐defined voids and ample pathways for ion diffusion. Furthermore, hierarchical nickel selenide/nickel telluride works synergistically at heterojunctions, providing a local ion enrichment mechanism for the catalytic process. As a result, Ni 0.85 Se/NiTe 2 @Ni‐NH@CC needs an overpotential of 69 and 240 mV to deliver a current density of 10 mA cm −2 for the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER), respectively, with an outstanding stability observed for over 100 h. Moreover, the Ni 0.85 Se/NiTe 2 @Ni‐NH@CC (+, −) device exhibits excellent overall water‐splitting performance with a cell voltage of 1.50 V at 10 mA cm −2 and can be operated steadily for >100 h at 100 mA cm −2 . Density functional theory (DFT) calculations indicate favorable kinetics for H‐adsorption at the selenotelluride heterojunction, thereby promoting the HER. This work highlights a new approach for designing a unique nanoarchitecture of MOF/hydroxide‐derived selenotelluride heterojunctions for high‐efficiency energy conversion applications.