Ni3S2/Co9S8 embedded poor crystallinity NiCo layered double hydroxides hierarchical nanostructures for efficient overall water splitting

Nickel-cobalt bimetallic layered double hydroxides (NiCo LDHs) are potential electrocatalysts with high performance and stability for overall water-splitting. However, its weak conductivity limits its practical applications. Herein, a simple hydrothermal in-situ conversion strategy is employed for constructing the novel heterogeneous electrocatalyst of Ni3S2/Co9S8 embedded poor crystallinity (Pc) NiCo LDH nanosheet arrays grown on the Ni foam (Pc-NiCo LDH/ Ni3S2/Co9S8), which can improve the conductivity via regulating the crystallinity. The crystallinity of NiCo LDH is well regulated by adjusting the amount of sulfur source, and the construction of Ni3S2/Co9S8 heterostructure exposes more active sites, improves the electrical conductivity, enhances the electronic interaction between NiCo LDH and Ni3S2/Co9S8, and significantly promotes the kinetics of water splitting. The optimized Pc-NiCo LDH/Ni3S2/Co9S8 hierarchical structure as both the anode and cathode exhibit the overall water splitting performance with the cell voltage of only 1.744 V to achieve the current density of 50 mA cm-2 in the alkaline media and shows the competitive H2 and O2 production rate of 6.4 and 3.1 μL s-1, respectively, suggesting its potential practical applications. This work provides a novel idea for the design of multiphase composite electrocatalysts applied in water splitting.