96 Towards a stable and inexpensive catalyst for OER in acid
for alkaline and acid based on the two hour tests at 1.8 and 1.9 VRHE. These
mass loss rates yield a fairly short lifetime for the lms which must be improved
if they are to be used in electrolyzers. Therefore a strategy for stabilization
was presented, including a short summary of a DFT study previously carried
out as a master project. The concept is based on terminating undercoordinated
sites that are likely to dominate in the dissolution process. TiO2 was found
to be a possible termination material, and was tested experimentally. Mixed
Ti-MnO2 lms, with 20 % Ti, were prepared by co-sputtering and characterized
with XPS and electrochemical tests. The mixed lms exhibited slightly lower
activities but also signicantly lower mass losses compared to the pure MnO2.
At 1.9 VRHE the mixed lms sustained 10 % lower current density, while the
mass losses were 40 % lower. Finally, the rate of cathodic dissolution, a very fast
process, was investigated for both mixed Ti-MnO2 and MnO2. The introduction
of Ti led to a more stable surface, which dissolved at around 25-30 mV more
cathodic potentials. The results presented here serve as a rst step towards
inexpensive catalysts for OER in PEM cells. It is not likely that the stability
improvements reached are enough to facilitate the use of Mn based catalysts
but to this author's best knowledge, it is currently the rst viable strategy to
stabilizing an OER catalyst for use in acid. With further optimization of the
preparation technique and a wider search for material combinations it could be
possible to reach the goal of a catalyst that is based on abundant elements.