Nanostructured MnMoO4 as a trifunctional electrocatalyst for overall water splitting and CO2 reduction

Electrochemical water splitting and CO₂ reduction are important processes to produce hydrogen and low–carbon fuels as renewable energy sources. Here, nanostructured MnMoO₄, prepared by the reflux precipitation method, was investigated as a trifunctional electrocatalyst for overall water splitting and CO₂ reduction reactions. Using a combination of diffuse reflectance spectroscopy and electrochemical impedance spectroscopy results, a direct band gap of 3.05 eV was obtained experimentally for the prepared MnMoO₄. An overpotential of 0.36 V at a current density of 5 mA cm⁻² and a Tafel slope of 58 mV dec⁻¹ were obtained for the oxygen evolution reaction. At a current density of 3 mA cm⁻², overpotentials of 0.39 V and 0.58 V were achieved in the absence and presence of CO₂ bubbling into a 0.1 M KOH solution, respectively, emphasizing the poisoning effect of CO₂ reduction intermediates for the hydrogen evolution reaction. Based on the obtained results, MnMoO₄ could be a promising electrocatalyst for water splitting and CO₂ reduction reactions.