One-step gas phase sulfided NiFe coating as self-supporting electrode for high efficiency oxygen evolution reaction

The development of cost-effective oxygen evolution reaction (OER) electrocatalytic electrodes is one of the essential means of applying green hydrogen energy. Due to the complex steps in the anodic OER, the high overpotential hinders the kinetics of water splitting. In this paper, the sulfided NiFe coating was innovatively designed as a self-supporting OER electrode by high-velocity oxygen fuel (HVOF) spraying coupled with one-step gas phase sulfuration. The thickness of the NiFe coating is approximately 20 μm. After the sulfuration treatment, the surface of the NiFe coating is remolded into a uniform rock sugar-like structure, and simultaneously forms new NiS and Ni3S4 phases. The sulfided NiFe coating electrode shows relatively low overpotentials of 220 mV and 253 mV at the current density of 10 mA cm−2 and 100 mA cm−2, respectively, and the Tafel slope is as low as 28.6 mV dec−1. The excellent electrocatalytic activity is mainly attributed to the synergistic effect of sulfides, the adsorption of OH− by the Ni3+ in alkaline electrolyte, and the acceleration of O2 separation by the S2− through promoting the cleavage of O–O bonds. In addition, the sulfided NiFe coating electrode also has a small charge transfer resistance, and the potential stability is as high as 98.1% in the 70 h stability test. Therefore, the development of sulfided transition metal coating electrodes can provide a new idea for the large-scale industrialization of water splitting.