Enhanced Interactions between Gold and MnO₂ Nanowires for Water Oxidation: A Comparison of Different Chemical and Physical Preparation Methods

Abstract

Oxygen evolution reaction (OER) has been considered as the bottleneck step in water electrolysis to simultaneously produce hydrogen and oxygen. The earth abundant first-row metal oxides such as manganese oxide have been found very active after anchoring nanoparticular noble metals such as Au, Pd and Pt onto its surface. Recent reports have demonstrated that Au can increase the turnover frequency (TOF) of MnOx more than 10 times for the OER due to the unique local interaction between Au and MnOx. Here, we conducted a detailed comparative study of different preparation methods on the OER activity of Au/MnO2 nanocomposites, including physical sputtering (PS), deposition–precipitation with urea (DPU), DP with NaOH (DPN) and deposition–reduction (DR) with NaBH4. Through carefully controlling the preparation conditions, we find chemical preparation methods (i.e., DPU and DPN) can achieve uniform growth of monodispersed Au nanoparticles on MnO2 nanowires (Au/MnO2) same as sputtering; moreover, the as-prepared Au–MnO2 by DPU and DPN shows stronger interaction than that by sputtering, thereby achieving higher OER performance. Delicate chemical valence change and conductivity improvement induced by such interaction are further quantified by conventional XPS, resistivity and impedance measurements.