Defective and ultrathin NiFe LDH nanosheets decorated on V-doped Ni3S2 nanorod arrays: a 3D core–shell electrocatalyst for efficient water oxidation

Water electrolysis utilizing renewable electricity power is a promising technology to produce green hydrogen energy on a large scale. However, this energy conversion technology is seriously hindered by the high activation barrier of the oxygen evolution reaction (OER), which requires highly active and robust electrocatalysts. Herein, we have developed a novel three-dimensional (3D) core–shell OER electrocatalyst, in which defective and ultrathin NiFe layered double hydroxide (NiFe LDH) nanosheets are rationally decorated on V-doped Ni3S2 nanorod arrays supported on Ni foam (V-Ni3S2@NiFe LDH). The highly conductive V-doped Ni3S2 nanorod cores ensure rapid charge transfer, and the ultrathin NiFe LDH nanosheets with rich defects offer numerous exposed active sites, together with the unique 3D core–shell nanostructures that benefit electrolyte diffusion and gas products releasing, thus our hierarchical catalyst is distinguished by very low overpotentials of 209 and 286 mV to obtain current densities of 10 and 100 mA cm−2, respectively, for OER in 1 M KOH. Impressively, when this 3D core–shell catalyst is paired with V-doped Ni3S2 nanorod arrays for overall water splitting, an outstanding two-electrode electrolyzer is achieved, which only requires 1.55 V to deliver a current density of 10 mA cm−2 in 1 M KOH, even superior to the benchmark of RuO2(+)//Pt(−). Our work provides a novel and effective strategy to rationally design efficient 3D hierarchical catalysts for energy conversion and storage.