This Ph.D. thesis presents work on non-noble metal oxide catalysts for the
oxygen evolution reaction, OER. This reaction is currently a bottleneck in electrolyzer
technologies, which are promising for energy storage purposes. In particular,
Polymer Electrolyte Membrane, PEM, cells are attractive for decentralised
hydrogen stations. PEM electrolyzers rely on scarce noble metals to
achieve high eciency and durability, which limits the scalability of the technology.
Finding new catalysts for OER is therefore a thriving research eld with
new materials being reported frequently.
However, many of these new reports include little information about stability,
which is evaluated solely from short term electrochemical testing. The rst
part of this project was therefore dedicated to designing a meaningful stability
protocol. Manganese oxide thin lms were prepared with sputter deposition and
the stability was evaluated with Electrochemical Quartz Crystal Microbalance
measurements combined with Inductively Coupled Plasma - Mass Spectrometry.
The results showed that a stable electrochemical performance can be achieved,
while a constant mass loss is occurring. The proposed protocol can guide future
research eorts in evaluating novel materials for the OER.
Unfortunately, most non-noble metal based OER catalysts reported to this
date work in alkaline solutions, where cheap NiFe electrodes are already utilized
in commercial systems. For acidic media, relevant for the acidic membrane in
PEM electrolyzers, there is a lack of strategies aimed at designing catalysts
without noble metals. It turns out that MnO2 is a stable material in the OER
relevant potential range in acid. In this project, MnO2 thin lms were therefore
prepared to evaluate their usefulness for PEM electrolyzers. Anodic dissolution
of MnO2 was found to be an issue and a strategy is presented for stabilizing the
surface. From density functional theory calculations it was found that titanium
could segregate to surface sites prone to dissolution. Thus, MnO2 thin lms
were modied with titanium using a reactive co-sputtering method and tested
in acid. The results indicate that the stability could be improved with more