Efficient coupling of a hierarchical V₂O₅@Ni₃S₂ hybrid nanoarray for pseudocapacitors and hydrogen production

Hierarchical materials are a favourite for energy storage/harvesting technologies, such as supercapacitors and electrically-driven hydrogen production. In this work, we report a robust and highly active nanomaterial for pseudocapacitors and hydrogen production by growing vanadium pentoxide on the surface of nickel sulfide (denoted as V₂O₅@Ni₃S₂). V₂O₅@Ni₃S₂ shows a capacitance of up to 854 F g^-1 at a current density of 1 A g^-1 and good rate capability. The capacitance can retain ca. 60% of the initial specific capacitance even after 1000 cycles at a current density of 1 A g^-1. For the hydrogen evolution reaction (HER), the overpotential of V₂O₅@Ni₃S₂ is around 95 mV at 10 mA cm^-2. The excellent electrochemical performance of the V₂O₅@Ni₃S₂ hybrid is attributed to the synergistic effect between vanadium pentoxide and nickel sulfide for pseudocapacitors, and the V₂O₅@Ni₃S₂ interface and V-S active bonding in the hierarchical structure for the HER. This work demonstrates an effective structure design for supercapacitors with high energy density and for efficient hydrogen production with high catalytic activity by incorporating metal oxide with metal sulfide.