Amorphous NiFe layered double hydroxide nanosheets decorated on 3D nickel phosphide nanoarrays: a hierarchical core-shell electrocatalyst for efficient oxygen evolution

The rational design of efficient and earth-abundant electrocatalysts for the oxygen evolution reaction (OER) plays a paramount role in hydrogen production by water electrolysis. Here we report a 3D hierarchical core-shell nanostructured OER electrocatalyst, in which amorphous NiFe layered double hydroxide (LDH) nanosheets are decorated on 3D conductive nickel phosphide nanoarrays. The integrated 3D core-shell electrode simultaneously offers excellent electrical conductivity for fast electron transfer, a large surface area with numerous active edge sites, and a hierarchical nanostructure for rapid release of gas bubbles, thus contributing to outstanding catalytic performance: low overpotentials (197, 243, and 283 mV for current densities of 10, 100, and 300 mA cm(-2), respectively), a small Tafel slope (46.6 mV dec(-1)), and superior stability, which are better than those of almost all reported LDH-based OER catalysts. When this hybrid catalyst is combined with nickel phosphide for overall water splitting, the two-electrode cell achieves current densities of 10 mA cm(-2) at 1.52 V and 100 mA cm(-2) at 1.68 V in alkaline media, which are even superior to those of benchmark IrO2 and Pt. This work paves an effective approach to design 3D hierarchical hybrid electrocatalysts for energy conversion and storage.