NiCo₂S₄ porous nanotubes are synthesised by a sacrificial template method based on the Kirkendall effect. The as-prepared NiCo₂S₄ nanotube electrode shows a specific capacitance of 1093 F g⁻¹ at a current density of 0.2 A g⁻¹ (933 F g⁻¹ at 1 A g⁻¹).

Designing low-cost and highly efficient bifunctional electrocatalysts for compatible integration with the hydrogen evolution reaction (HER) and the oxygen evolution reaction (OER) for overall water splitting is critical but challenging. Herein, mutually beneficial Co₃O₄@MoS₂ heterostructures were adopted to efficiently balance both HER and OER performance by improving the sluggish kinetics. These heterostructures synergistically favoured the reduction of the energy barrier of the initial water dissociation step and optimization of the subsequent H adsorption/desorption for MoS₂ in alkaline HER. Moreover, the adsorption of oxygen intermediates was enhanced for Co₃O₄ in the OER process. As a result, the Co₃O₄@MoS₂ heterostructures showed excellent overall water splitting performance with a low overpotential and Tafel slope.