Developing efficient and cost-effective bifunctional catalytic electrodes is of great importance to water splitting. In this study, hybrid Ni/Ni­(OH)2-coated NiCo2O4 nanorods were grown on Ni foam (NF) by a facile growth–conversion–epitaxy approach. The epitaxial decoration of Ni/Ni­(OH)2 composite could increase the intrinsic activity of NiCo2O4/NF and enhance the charge-transfer rate. This self-standing hierarchical nanohybrid with unique surface chemistry and interface engineering exhibits an excellent electrocatalytic performance. The optimized Ni/Ni­(OH)2-NiCo2O4/NF only requires overpotentials of 53 and 235 mV to reach a current density of 10 mA cm–2 for HER and OER, respectively. The electrolyzer achieved 10 mA cm–2 at a low cell voltage of 1.51 V for water splitting. This work offers a new perspective for rationally designing electrocatalytic materials by surface decoration.

Crystal structures and chemical states can be reconstructed by inducing the positioning growth of metal sulfide, which is an efficient strategy to enhance the oxygen evolution activity of an anode. In this paper, polysulfide (Poly(S-r-DIB))induced S-doped hierarchical heterostructures Ni 3 S 2 /NiCo 2 S 4 were successfully grown on nickel foam (Ni 3 S 2 /NiCo 2 S 4 /NF) by an in situ solvothermal sulfuration reaction using polysulfide as the sulfur source. The unique hierarchical heterostructure and strong electron interaction in Ni 3 S 2 @NiCo 2 S 4 /NF increased the catalytic activity area and provided more mass transfer channels for electron transfer to facilitate water splitting. As-prepared Ni 3 S 2 /NiCo 2 S 4 / NF exhibits excellent electrocatalytic activity for oxygen evolution reaction (OER) with an ultralow overpotential of 330 mV to reach 100 mA cm −2 and a small Tafel slope of 67.6 mV dec −1 , which is superior to most reported nickel-based sulfide electrocatalysts. This study provides not only a new method for the design of hierarchical nanomaterials but also an efficient strategy to design efficient OER electrocatalysts by an in situ polysulfide confinement method.

As the climate warms and energy scarcity becomes increasingly severe, the search for greener and more sustainable energy sources has attracted widespread attention. This hierarchical dandelion-like structure catalyst exhibits excellent hydrogen evolution properties.