Electrochemical Synthesis and Optimization of Co-Ni-Mn Catalyst for Oxygen Evolution Reaction

Aside from the high energy consumption of the modern society, the burning of fossil fuels has led to an environmental crisis that demands sustainable and carbon-free energy sources. Green hydrogen production, especially via water electrolysis, is a promising technology for the energetic transition. First-row transition metal-based electrocatalysts are promising due to their cost-effectiveness and abundance. Many approaches are described to improve the OER activity and stability of the electrocatalysts, one that has recently gained great attention is the combination of different elements. Trimetallic oxides based on Mn-Co-Ni have emerged as promising electrocatalysts for OER and has shown superior efficiency over the bimetallic and monometallic analogs. Herein, films of Mn-Co-Ni oxides were prepared by electrodeposition, via chronoamperometry, and subsequently activated by electrochemical activation by cyclic voltammetry (CV). The Mn-Ni-Co films were characterized by X-ray diffraction, Raman spectroscopy, scanning and transmission electron microscopy, and atomic force microscopy. Electrochemical characterization involved CV and electrochemical impedance spectroscopy. The electrodeposited Mn-Ni-Co hybrid films exhibited lower overpotential compared to benchmark catalysts and all individual oxide films. The Mn-Ni-Co film shows low overpotential of 430 mV at 25 mA cm⁻² and a Tafel slope 104 mV dec⁻¹, respectively. The high activity of the trimetallic film was attributed to the lower electron transfer resistance, high electrochemical active surface area, high intrinsic activity, in comparison to the monometallic films. Furthermore, the film was stable up to 2 h at a density current of 100 mA cm⁻² and provided a high Faradaic efficiency. In conclusion, the Mn-Ni-Co electrocatalysts prepared by electrodeposition and activated electrochemically are promising materials to promote the water splitting for green hydrogen production.