2.5 Oxygen Evolution 39
which all dissolve upon reduction, although at a much lower rate compared to
Ru.
Figure 2.13: Figure showing the stability of Ru, Ir, Pt and Au under OER reaction
conditions, from top to bottom respectively. The mass losses are measured with online
Inductively Coupled Plasma-Mass Spectrometry systems and are plotted as function
of time. The potential is indicated with the lines and second axes on the right. In
this way, it is possible to directly correlate the amount of mass lost to the potential
applied to the electrodes. Figure taken from 179.
With such a dissolution prole it is unlikely that Ru can be used in electrolyzers.
Instead Ir appears as the best compromise between activity and stability.
In fact, through annealing procedures it has been shown that IrOx can be even
more stable, reaching a mass loss rate of only 1 pg/cm2/s at approximately 1.75
VRHE 180. For a realistic catalyst loading of 0.15 mg/cm2 41 this corrosion
rate corresponds to just below 5 years of constant operation. However, since