36 Electrocatalysis and the splitting of water
Mn2O3
E-dep.
0,250,300,350,400,45
100
10
1
0,1
Ni0.78Fe0.22(OH)2
Ni0.95Fe0.05(OH)2
h/V
jgeo/mA.cm-2
Pr0.5Ba0.5CoO3- d#
Fe0.3Co0.3Ni0.3Ox
½μmRuO2-Ni
BSCF#Co3O4NP
SputteredMnOx
Ni0.9Fe0.1Ox
Ir/C
SputteredRuOxRuOAlkaline2(100)#
Figure 2.11: Overview plot of recent experiments with OER catalysts tested in
alkaline media. Ni0:78Fe0:22(OH)2 is from 149, Fe0:3Co0:3Ni3Ox is from 144, RuO2-
Ni is from 104, Pr0:5Ba0:5CoO3�� is from 140, Ni0:95Fe0:05(OH)2 is from 147,
Ni0:9Fe0:1Ox is from 150, Ir/C is from 151, BSCF is from 139, RuO2(100) is from
122, Co3O4 is from 152 and Mn2O3 E-dep is from 151. Sputtered RuOx and MnOx
is from this project. # denotes that the surface area is evaluated from particle size
analysis instead of geometric.
catalytically active 138.
Some of the rst manganese based OER catalysts to be reported were made with
thermal decomposition, inspired by the success of DSAsr, by Morita et al. in
1977-79 158160. It was concluded that both -MnO2 and -Mn2O3, on either
Ti or Pt, and their mixtures could be used as anodes for oxygen evolution, even
though they were inferior to RuO2 based electrodes. The electrodes were tested
in both acid and alkaline electrolytes. Ti substrates yielded better adhesion for
the catalyst, while using a Pt substrate resulted in better conductivity. It was
further speculated that oxygen vacancies in the catalyst layer provide the necessary
conductivity, which decreases upon prolonged oxidation of the electrode
due to an increase of oxygen content. This eect could be responsible for a slow
deactivation of the catalyst activity when measured at high current density or
potential over time. The existence of various Mn oxides (MnO, Mn3O4, Mn2O3,
MnO2 and several dierent crystalline phases) has also lead to studies on the
inuence of the initial oxide on the OER activity, so-called structure-activity