The intervening barrier to produce hydrogen from water is the frustratingly slow kinetics of the water splitting reaction. In addition, insufficient understanding of the key obstacle of the oxygen evolution reaction (OER) is an obstruction to perceptive design of efficient OER electrocatalysts. In this research, we present synthesis, characterization, and electrochemical evaluation of nickel oxide/nickel sulfide (NiO/NiS) heterostructures and its counterparts nickel oxide (NiO) and nickel sulfide (NiS) as low-cost electrocatalysts for electrochemical water splitting. These electrocatalysts have been characterized using powder X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, and scanning electron microscopy (SEM). The NiO/NiS is found to be highly efficient and stable electrocatalyst, which initiates the OER at an amazingly low potential of 1.42 V (vs RHE). The NiO/NiS electrocatalyst provides a current density of 40 mA cm–2 at 209 mV overpotential for OER in 1.0 M KOH with a Tafel slope of 60 mV dec–1, outperforming its counterparts (NiO and NiS) under same electrochemical conditions. These results are better than those of benchmark Ni-based and even noble metal-based electrocatalysts. The continued oxygen generation for several hours with an applied potential of 1.65 V (vs RHE) reveals the long-term stability and activity of NiO/NiS electrocatalyst toward OER. This development provides an attractive non-noble metal, highly efficient, and stable electrocatalyst toward OER.

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