Understanding interactions between manganese oxide and gold that lead to enhanced activity for electrocatalytic water oxidation

To develop active nonprecious metal-based electrocatalysts for the oxygen evolution reaction (OER), a limiting reaction in several emerging renewable energy technologies, a deeper understanding of the activity of the first row transition metal oxides is needed. Previous studies of these catalysts have reported conflicting results on the influence of noble metal supports on the OER activity of the transition metal oxides. Our study aims to clarify the interactions between a transition metal oxide catalyst and its metal support in turning over this reaction. To achieve this goal, we examine a catalytic system comprising nanoparticulate Au, a common electrocatalytic support, and nanoparticulate MnO_x, a promising OER catalyst. We conclusively demonstrate that adding Au to MnO_x significantly enhances OER activity relative to MnO_x in the absence of Au, producing an order of magnitude higher turnover frequency (TOF) than the TOF of the best pure MnO_x catalysts reported to date. We also provide evidence that it is a local rather than bulk interaction between Au and MnO_x that leads to the observed enhancement in the OER activity. Engineering improvements in nonprecious metal-based catalysts by the addition of Au or other noble metals could still represent a scalable catalyst as even trace amounts of Au are shown to lead a significant enhancement in the OER activity of MnO_x.