Ni3S2 nanorods growing directly on Ni foam for all-solid-state asymmetric supercapacitor and efficient overall water splitting

Transition metal compounds are attractive for their significant applications in supercapacitors and as non-noble metal catalysts for electrochemical water splitting. Herein, we develop Ni3S2 nanorods growing directly on Ni foam, which act as multifunctional additive-free Ni3S2@Ni electrode for supercapacitor and overall water splitting. Based on PVA-KOH gel electrolyte, the assembled all-solid-state Ni3S2@Ni//AC asymmetric supercapacitor delivers a high areal energy density of 0.52 mWh cm−2 at an areal power density of 9.02 mW cm−2, and exhibits an excellent cycling stability with a capacitance retention ratio of 89% after 10000 GCD cycles at a current density of 30 mA cm−2. For hydrogen evolution reaction and oxygen evolution reaction in 1 M KOH, Ni3S2@Ni electrode achieves a benchmark of 10 mA cm−2 at overpotentials of 82 mV and 310 mV, respectively. Furthermore, the assembled Ni3S2@Ni||Ni3S2@Ni electrolyzer for overall water splitting attains a current density of 10 mA cm−2 at 1.61 V. The in-situ synthesis of Ni3S2@Ni electrode enriches the applications of additive-free transition metal compounds in high-performance energy storage devices and efficient electrocatalysis.