Urea‐Assisted N‐Doping of Nickel Sulfide for Enhanced Oxygen Evolution Reaction Performance

The oxygen evolution reaction (OER) limits the efficiency of electrochemical water splitting, making the development of low‐cost, stable, and efficient catalysts a key challenge. In this work, nickel sulfide (NiS ₂ ) nanostructures are grown on cone‐shaped graphite electrodes and further modified via annealing in the presence of urea or NaH ₂ PO ₂ , introducing N or P element to alter the electronic environment around Ni ²⁺ centers. Comprehensive characterization (XRD, FE‐SEM, EDX, ICP‐AES, XPS, and electrochemical techniques) confirms successful doping. The OER activity follows the trend N‐NiS ₂ > S‐NiS ₂ > P‐NiS ₂ , correlating with the elemental electronegativity order of N > S > P. N‐doped NiS ₂ achieves a low overpotential of 260 mV at 10 mA cm ⁻² and a Tafel slope of 53 mV dec ⁻¹ in 1 M KOH. Urea‐derived ammonia treatment creates a porous, high‐surface‐area architecture that enhances easy mass transport and catalytic efficiency. This simple, scalable strategy presents a cost‐effective route to high‐performance OER electrocatalysts.