Formation of Nickel Sulfide Nanoframes from Metal-Organic Frameworks with Enhanced Pseudocapacitive and Electrocatalytic Properties

Nanoframe-like hollow structures with unique threedimensional (3D) open architecture hold great promise for various applications. Current research efforts mainly focus on frame-like noble metals and metal oxides. However, metal sulfides with frame-like nanostructures have been rarely reported. Starting from metal-organic frameworks (MOFs), we demonstrate a novel structure-induced anisotropic chemical etching/anion exchange method to transform Ni-Co Prussian blue analogue (PBA) nanocubes into NiS nanoframes with tunable size. The reaction between Ni-Co PBA nanocube templates and Na2S in solution leads to the formation of welldefined NiS nanoframes. The different reactivity between the edges and the plane surface of the Ni-Co PBA nanocubes is found to be the key factor for the formation of NiS nanoframes. Benefitting from their structural merits including 3D open structure, small size of primary nanoparticles, high specific surface area, and good structural robustness, the as-derived NiS nanoframes manifest excellent electrochemical performance for electrochemical capacitors and hydrogen evolution reaction in alkaline electrolyte.