Electrochemically embedded heterostructured Ni/NiS anchored onto carbon paper as bifunctional electrocatalysts for urea oxidation and hydrogen evolution reaction

Abstract

Developing high-efficiency, cost-effective, and long-term stable nanostructured catalysts for electrocatalytic water splitting remains one of the most challenging aspects of hydrogen fuel production. Urea electrooxidation reaction (UOR) can produce hydrogen energy from nitrogen-rich wastewater, making it a more sustainable and cheaper source of hydrogen. In this study, we have developed Ni/NiS hybrid structures with cauliflower-like morphology on carbon paper electrodes through the application of dimethylsulfoxide solvents. These electrodes serve as highly efficient and long-lasting electrocatalysts for the hydrogen evolution reactions (HER) and UOR. In particular, the Ni/NiS cauliflower-like morphology is confirmed via X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM). Furthermore, electrochemical characterization of the Ni/NiS@CP catalyst showed a 1.35 V onset potential versus RHE for the UOR in 1.0 M KOH and superior electrocatalytic performance compared to bare Ni@CP. Additionally, the Ni/NiS@CP catalyst also exhibits a low overpotential of 125 mV at 10 mA cm⁻² for HER in 0.5 M H₂SO₄ with excellent durability, which is apparently lower than bare Ni@/CP (397 mV). Based on the results obtained, the synthesized Ni/NiS@CP catalyst may be a promising electrode candidate for handling urea-rich wastewater and generating hydrogen.