84 Towards a stable and inexpensive catalyst for OER in acid
a)Mn2pintestedsample
Mn2pinas-prepared
sample
670665660655650645640
10000
8000
6000
4000
2000
0
670665660655650645640
10000
0
8000
6000
4000
2000
BindingEnergy/eV
470465460455
3000
2500
2000
1500
1000
500
0
470465460455
3000
2500
2000
1500
500
0
1000
b)
Counts
Counts
c)d)
BindingEnergy/eV
Counts
Ti2pinas-prepared
sample
BindingEnergy/eV
Ti2pintestedsample
Counts
BindingEnergy/eV
Figure 5.6: XPS measurements of the Mn2p and Ti2p peaks for Ti-MnO2 lms.
a) Mn2p for the as-prepared sample. b) Mn2p for the tested sample. c) Ti2p for the
as-prepared sample. d) Ti2p for the tested sample. These peaks were intergrated and
used for quantication of the Ti content.
attached to aluminium stubs for the microscope stage. Since these substrates
consist of a thin gold lm on electronically insulating quartz it is critical to
ensure that the lm has optimal electronic contact to the stub. To avoid charging
eects from the electron beam, silver paste was used to glue the samples to the
stubs and only a small area of thin lm was left visible. In gure 5.7a-d images
of the surfaces can be seen.
The surface of an as-prepared MnO2 thin lm consists of small, elongated, platelike
structures in the size of approximately 10-20 nm, as shown in gure 5.7a.
At the same time the structures seem densely packed and are not likely to
contribute to a high roughness factor compared to electrodeposited samples or
electrodes prepared by thermal decomposition 45, 151. In gure 5.7b the surface
of a tested MnO2 lm is shown and, compared to the as-prepared sample,
there are only minor dierences. The structures seem slightly more elongated
and possibly a bit less densely packed. However, no dramatic changes has been
induced from the electrochemical test. In gure 5.7c an as-prepared Ti-MnO2
lm can be seen, which again looks very similar to the pure MnO2 lm. The
same plate-like features are visible. Finally, in gure 5.7d, a tested Ti-MnO2