Au-manganese oxide nanostructures by a plasma-assisted process as electrocatalysts for oxygen evolution: a chemico-physical investigation

Earth-abundant and eco-friendly manganese oxides are promising platforms for the oxygen evolution reaction (OER) in water electrolysis. Herein, a versatile and potentially scalable route to gold-decorated manganese oxide-based OER electrocatalysts is reported. In particular, MnxOy (MnO2, Mn2O3) host matrices are grown on conductive glasses by plasma assisted-chemical vapor deposition (PA-CVD), and subsequently functionalized with gold nanoparticles (guest) as OER activators by radio frequency (RF)-sputtering. The final selective obtainment of MnO2- or Mn2O3-based systems is then enabled by annealing under oxidizing or inert atmosphere, respectively. A detailed material characterization evidences the formation of high-purity MnxOy dendritic nanostructures with an open morphology and an efficient guest dispersion into the host matrices. The tailoring of MnxOy phase composition and host-guest interactions has a remarkable influence on OER activity yielding, for the best performing Au/Mn2O3 system, a current density of ca. 5 mA cm-2 at 1.65 V versus the reversible hydrogen electrode (RHE) and an overpotential close to 300 mV at 1 mA cm-2. Such results, comparing favorably with literature data on manganese oxide-based materials, highlight the importance of compositional control, as well as of surface and interface engineering, to develop low-cost and efficient anode nanocatalysts for water splitting applications.