Chapter 5
Towards a stable and
inexpensive catalyst for
OER in acid
Sustainable production of hydrogen with electrolyzers has the potential to alleviate
issues with uctuating power supply from renewable sources, such as
wind and solar power. As described in the introduction, Polymer Electrolyte
Membrane cells, PEM, are particularly attractive due to their compact and simple
design, fast start up and unmatched ionic conductivity. However, a major
drawback is the extensive use of noble metal based catalysts for the oxygen
electrode, the anode. For the hydrogen electrode, the search for non-precious
materials has been a thriving research eld for years with a large variety of
interesting materials being identied as alternatives to platinum 57, 210. This
is not the case for the anode where, currently, there are no alternatives to precious
metal oxides in acidic media. Furthermore, the loading of Ir constitutes
a much larger issue compared to the extremely low loading of Pt used on the
hydrogen electrode 41. Most new and active catalysts that are active for OER
in alkaline environment are based on Ni, Fe and Co. These transition metals
are unfortunately not stable as solid phases in acidic environment 138. Conversely,
MnO2, an intensely studied material due to its abundance and role in
Photosystem II 155, 161, is stable as a solid phase in acidic pH from 1.3 to 1.7
VRHE 138. This potential range is important for water oxidation as it spans
the range where an anode in an electrolyzer would operate. Although active,
MnO2 requires a signicant overpotential to drive the oxygen evolution reaction