Draft version
DRAFT
In-situ investigation of Au-MnOx thin films with
improved activity for the oxygen evolution
reaction
Rasmus Frydendal,a Linsey Seitz,b Dimosthenis Sokaras,c Tsu-Chien Weng,c Dennis Nordlund,c Ib Chorkendorff,a
Ifan E.L. Stephens, a Thomas F. Jaramillo,b,c
a Center for Individual Nanoparticle Functionality, Department of Physics, Building 312, Technical University of
Denmark, DK-2800 Kgs. Lyngby, Denmark
b Department of Chemical Engineering, Stanford University, Stanford, California 94305, United States
c SLAC National Accelerator Laboratory, 2575 Sand Hill Road, Menlo Park, California 94025, United States
Abstract
The electrochemical splitting of water holds great potential as a method for producing clean fuels by storing
electricity from intermittent energy sources. The efficiency of such a process would be greatly facilitated by
incorporating more active catalysts based on abundant materials for the oxygen evolution reaction.
Manganese oxides are promising as catalysts for this reaction. Recent reports show that their activity can be
drastically enhanced when modified with gold. Herein, we investigate highly active mixed Au-MnOx thin films
for the oxygen evolution reaction, which perform more than five times better than the pure MnOx. These films
are thoroughly characterized with in-situ X-ray Absorption, which reveal that Mn assumes a higher oxidation
state under reaction conditions when Au is present. At the same time, the magnitude of the enhancement is
correlated to the size of the Au domains where larger domains are the most beneficial. These observations
serve as a solid starting point for better understanding of the beneficial interaction between gold and
manganese oxide.
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