Au–Manganese Oxide Nanostructures by a Plasma‐Assisted Process as Electrocatalysts for Oxygen Evolution: A Chemico‐Physical Investigation

Abstract 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, Mn_xO_y (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 Mn_xO_y dendritic nanostructures with an open morphology and an efficient guest dispersion into the host matrices. The tailoring of Mn_xO_y 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 ≈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.