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

Abstract

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.