Surfactant-assisted synthesis of nickel sulfide as bi-functional catalyst for water splitting application

Different catalysts have been designed and synthesized using various approaches for efficient water splitting. This study uses a surfactant-assisted hydrothermal approach to synthesize different morphologies and phases of nickel sulfide. The synthesized materials were characterized by FTIR, XRD, and SEM. The relation between shape, size, phases of nickel sulfide, and their electrocatalytic behavior were studied. The catalyst with rod-shaped geometry showed good catalytic activity towards hydrogen evolution reaction (HER) with a Tafel slope of 123 mV dec-1 and an overpotential of 62.4 mV at a current density of 10 mA cm- 2. The other sample with a tlake shape appearance showed commendable activity towards oxygen evolution reaction (OER) with an overpotential of 287 mV at the current density of 40 mA cm-2 and a Tafel slope of 118.4 mV dec-1. This material could effectively drive water splitting into H2 and O2 at a voltage of 1.32 V in a two-electrode configuration, and long-term stability was verified for 50 h with a small loss in the current density. This environment-friendly method opens up a new way to synthesize nickel sulfide and elaborates the relation between morphology and electrocatalytic behavior.