Chapter 4
Benchmarking the stability
of OER catalysts
The development of new catalysts for the oxygen evolution could have a signi-
cant impact on the eciency and commercialization of electrolyzers. Therefore,
a lot of eort is put into identifying active mixed oxides with novel structures or
stoichiometries. However, in the testing of these catalysts the stability is typically
evaluated on the basis of stable electrochemical performance for a short
period of time. This type of screening rules out instantaneous dissolution of the
catalyst but does not ensure lifetime beyond the hours tested. In fact, for a
given catalyst with a slow dissolution rate during operation there is no way to
know beforehand whether the dissolution will result in better or worse performance
until a signicantly lower amount of active surface area is reached. To
truly gauge the lifetime of a newly identied catalyst one is left with choosing
between long term testing or directly measuring the rate of mass loss. Long
term testing is often tedious and in this chapter it will be shown how to directly
measure the rate of mass loss using short term tests 137. The results presented
here are also the basis of the appended paper I, where measurements on RuO2
are included.
4.1 Characterization of thin lms
The investigated samples are manganese oxide thin lms deposited with the
sputter deposition technique described in section 3.1.1. Specically, these lms
are grown to be 40 nm thick, in a 5 mTorr atmosphere consisting of argon