Crystalline-Amorphous Ni₃Se₄-Ni Hydroxide Heterostructure as an Efficient Electrocatalyst for Oxidation Evolution Reaction

Developing low-cost Ni-based amorphous/crystalline composites with well-defined nanostructures is expected to achieve a highly efficient oxygen evolution reaction(OER) by exposing more active sites and enhancing the electrical conductivity, but it still remains a synthetic challenge. Here, a crystalline/amorphous composite composed of crystalline Ni₃Se₄ and amorphous Ni hydroxide with a multi-layered bowl-shaped nanostructure was synthesized by a simple one-step solvothermal method. By regulating the concentration of sulfate ions in the reaction solution, the single-layered nanosheets achieve a transformation into a multi-layered structure with more exposed active sites. In addition, the crystalline-amorphous heterostructure allows regulation of the interfacial electronic structures, and the decoration of Ni₃Se₄ can effectively enhance the electrical conductivity of composites. Benefiting from the interfacial synergy between Ni₃Se₄ and Ni hydroxide, the as-optimized Ni₃Se₄/Ni hydroxide as an OER catalyst displayed superior electrocatalytic activity with a low overpotential of 285 mV at a current density of 10 mA/cm², a small Tafel slope of 68.3 mV/dec and remarkable stability in alkaline solution. This work offers a novel and effective method for the design of functional crystalline/amorphous composites for energy conversion and storage.[Figure not available: see fulltext.]