2.5 Oxygen Evolution 33
Ru70Ir30NP
0,200,250,300,350,40
100
10
1
0,1
0,01
RuO2NP#
PtIrNSTF,80oC
/V
jgeo/mA.cm-2
Rupc
IrNP
Irpc
RuNP
Acid
Ru60Co40NP
IrO2NP#
SputteredRuO2
Ir-ND/ATO
IrNi3.3NPs
Figure 2.9: Overview plot of recent studies on OER catalysts tested in acidic media.
Ru polycrystalline sample (pc), Ru NP, Ir pc and Pt pc are from 100. PtIr
NanoStructured Thin Film (NSTF) is from 41. Ru70Ir30 NP and Ru60Co40 NP are
from 106. IrNi3:3 is from 134. Ir-ND/ATO (antimony-doped tin oxide) is from 136.
RuO2 NP and IrO2 NP are from 101, where the current is normalised to an area estimated
from particle size analyses, indicated by #. Sputtered RuO2 is from 137,
which is appended as paper I.
2.5.2.1 Progress in alkaline media
A far larger group of materials can withstand the reaction conditions in alkaline
electrolytes. This is quickly realized by scanning through the Pourbaix diagrams
of the elements, where most stable compounds are shown as function of pH and
electrochemical potential 138. A renewed interest in perovskite materials has
been taken by the group of Shao-Horn, who tested a set of oxides with the
aim of nding design principles for activity towards OER 139. Inspired by
the earlier work of Bockris and co-workers 83, they attempted to identify a
suitable bulk property that could relate to the OER activity of a group of
perovskites. They successfully constructed a volcano shaped activity plot based
on the lling of the eg band and identied Ba0:5Sr0:5Co0:8Fe0:2O3��x as a highly
active catalyst. The eg band lling was argued to be a suitable descriptor for
OER due to strong overlap of this particular orbital with the oxygen adsorbate
orbital. Thus, the eg band lling should have a direct implication in the charge
transfer from electrode to adsorbate and inuence the binding strength. An
optimum eg band lling of 1 was proposed. Due to diculties in measuring and