Nickel sulphide decorated nitrogen rich ordered mesoporous carbon (NOMC) as an efficient catalyst for the electrocatalytic oxidation of urea in alkaline medium

The urea oxidation reaction (UOR), as a feasible alternative for the slow oxygen evolution reaction (OER), is recognized as an encouraging puissant approach for hydrogen generation through water splitting. The route also offers excellent potential for hydrogen production through wastewater remediation. Here, a simple synthetic strategy has been adopted to embed NiS in a nitrogen-rich stable and activated mesoporous carbon matrix (NOMC) that has been successfully exploited for UOR. The NOMC supported nickel sulfide catalyst with high electrochemically active surface area (ECSA) exhibits a very good response towards the electro-catalytic oxidation of urea in an alkaline medium with a low working oxidation potential (potential corresponding to the current density value of 10 mA/cm2 taken as a standard) of 1.34 V (vs. RHE). The introduction of heteroatom (N) to the mesoporous carbon support and subsequent incorporation of metal sulfide rather than metal oxide or metal hydroxide, as reported previously, is done purposefully to increase the electrocatalytic activity of the catalyst through the synergistic effects of charge density with carbon support. The synergism is further supported by the comparative response in urea oxidation reaction (UOR) for NiS/NOMC catalyst compared to other Ni-based catalysts like Ni(OH)2, NiS, and NiS/CMK-3, which indicates that the activity is highest for NiS/NOMC. The catalyst attains good stability in an alkaline medium. The mesoporous carbon framework (NOMC) with considerably high BET surface area, large pore volume, and interconnected ion diffusion channels accelerate the transport of electrons through the porous surface, which makes NiS/NOMC highly efficient and stable as an electrocatalyst for the oxidation of urea in comparison to its other composite catalysts in alkaline medium.