Enhancing Oxygen\nEvolution Reaction Performance with\nrGO/CoNi-Prussian Blue-Derived Oxyhydroxide Nanocomposite Electrocatalyst:\nA Strategic Synthetic Approach

Electrochemical water splitting is a promising approach\nin the\ndevelopment of renewable energy technologies, providing an alternative\nto fossil fuels. It has attracted considerable attention in recent\nyears. The benchmark materials used in water splitting are precious\nmetals that are expensive and scarce. Therefore, this work proposes\na strategic electrochemical synthesis of a reduced graphene oxide\nand cobalt–nickel hexacyanoferrate (rGO/CoNiHCF)-derived composite\n(rGO/CoNiPBd-OOH) to achieve optimized OER performance. The optimum\nrGO/CoNiHCF was fabricated with the Co:Ni precursors in a 3:1 ratio\nwith a ferricyanide solution of pH = 1.0. Using an alkaline electrochemical\ntreatment, the well-distributed globular particles of CoNiHCF over\nrGO sheets were converted into layered frameworks of metallic (oxy)hydroxide\nspecies, giving the final rGO/CoNiPBd-OOH nanocomposite. This nanocomposite\npresented favorable kinetic activity resulting in a Tafel slope of\n33 mV dec<sup>–1</sup>, while rGO, CoNiPBd-OOH, and RuO<sub>2</sub> exhibited slopes of 80, 47, and 51 mV dec<sup>–1</sup>, respectively. Although the benchmark RuO<sub>2</sub> electrocatalyst\nshowed a lower overpotential (240 mV dec<sup>–1</sup>) at a\ncurrent density of 10 mA cm<sup>–2</sup>, the rGO/CoNiPBd-OOH\nperformed well with an overpotential of 346 mV, combined with superior\nstability compared to CoNiPBd-OOH and RuO<sub>2</sub>, maintaining\na current density of 10 mA cm<sup>–2</sup> for 15 h with an\noverpotential loss of 6.92%. This work successfully presents an “all-electrochemical”\nsynthesis of a rGO/CoNiHCF-derived material with remarkable electrocatalytic\nactivity for OER assisted by a strategic preparation methodology,\nwhich helped to understand the influence of synthetic parameters and\nchoose their conditions to achieve the optimum OER performance.