88 Towards a stable and inexpensive catalyst for OER in acid
Figure 5.10: Mass change over time for MnO2, blue, and Ti-MnO2, red, during two
hour chronoamperometry test at 1.9 VRHE in 0.05 M H2SO4. The change in mass is
based on measuring the frequency change with the EQCM. The shaded areas indicate
1 standard deviation from three independent measurements.
Activityafter1hour
0.05MH2SO4
1,81,9
a)10
8
6
4
2
0
Ti-MnO2
jgeo/mA.cm-2
U-iR/V(vs.RHE)
Ti-MnO2
MnO2
MnO2
1,81,9
-400
-800
0
-1200
-1600
-2000
MnO2
b)
Ti-MnO2
Ti-MnO2
MasslossfromICP-MS
2hourtests
Masschange/ngOxide.cm-2
U-iR/V(vs.RHE)
MnO2
Figure 5.11: a) Activity of MnO2 and Ti-MnO2 supported on Au polycrystalline
disks at 1.8 and 1.9 VRHE measured in 0.05 M sulfuric acid. The activity is compared
as the current density measured one hour into the test. b) Mass losses of MnO2
and Ti-MnO2 at 1.8 and 1.9 VRHE. The mass losses here are based on ICP-MS
measurements before and after each two hour test. For both graphs MnO2 results are
shown in blue and Ti-MnO2 in red. Error bars indicate 1 standard deviation from
three independent measurements.
decreased signicantly more than the 20 %, indicating that a better compromise
between stability and activity can be reached through the Ti modication.
At the same time the XPS measurements showed that there is no enrichment
of Ti in the surface after electrochemical testing. This is important since a