16 Introduction
Chapter 3 encompasses experimental methods that have been used throughout
this work. A small introduction to each method will be given along with
how it has been employed here.
Chapter 4 represents the rst main project. In the eld of oxygen evolution
new catalysts are reported rapidly but there is often a lack of tests dedicated
to investigating mass loss processes. The aim of this chapter is to highlight the
importance of stability testing for electrocatalysts. Here a viable test protocol
is presented and used for a MnOx thin lm catalyst.
Chapter 5 introduces a new strategy for stabilization of a non-noble metal
oxygen evolution electrocatalyst. The goal is to operate this catalyst in acidic
environment, where currently only noble metal oxides can be used. As mentioned
earlier in the introduction, the scale up of PEM electrolyzers suers from
the expensive and scarce materials used as catalysts for oxygen evolution. Our
stabilization strategy is based on blocking the sites responsible for dissolution
and this is tested experimentally for titanium modied MnO2, prepared with
reactive sputter deposition.
Chapter 6 addresses activity improvements for gold modied MnO2 as catalyst
for the oxygen evolution reaction. On a conceptual basis, reasons for activity
enhancements reported in the literature are discussed and recent Density
Functional Theory calculations are briey introduced. From an experimental
approach co-deposited Au-MnOx thin lms are characterized electrochemically
and with in-situ X-ray Absorption Spectroscopy. A particular focus is put on
the valency of Mn under reaction conditions when gold is present.
Chapter 7 presents the main conclusions described in the previous chapters
and nally, a small outlook section nalizes this thesis.
The main papers and manuscripts produced during this project are appended
after the bibliography.