A Facile Route Fabricated Nickel-Nitrogen-Doped Carbon Nanoparticle Based Electrocatalysts for the Oxygen Evolution and Hydrogen Evolution Reactions

The cost-effective hydrogen production via electrolyser depends on the availability of highly efficient, low-cost, and robust OER and HER catalysts. We fabricated Ni−NC and NC electrocatalysts via a simple, cheap, and scalable by direct mixing route followed by carbonization at 900 °C under the N₂ atmosphere. The addition of Ni into NC substantially increases the crystallite size, particle size, and I_D/I_G ratio. The Ni−NC sample exhibits excellent bifunctional OER and HER activities. The overpotentials to achieve (−) 10 mA.cm⁻² current density for the OER were 400 mV and 263 mV for the HER in 0.1 M NaOH electrolyte. The Tafel slope analysis of the Ni−NC sample for the OER (123 mV.dec⁻¹) revealed the hydroxyl-ion discharge is the rate-determining step. In comparison, for the HER (145 mV.dec⁻¹), the Volmer-Heyrovsky pathway is the rate-determining step. The short-term stability test displayed the sustained current density for 10 h at 1.68 V vs. RHE.