Structural and Phase Engineering of a Hierarchical 2D–2D Nickel MOF/Hydroxide‐Derived Ni_0.85Se/NiTe₂ Heterointerface for Robust HER, OER, and Overall Water Splitting

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_0.85Se/NiTe₂@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_0.85Se/NiTe₂@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.