Electrochemical reduction of NOx - DTU Orbit

4 DRIFT study of NOx adsorption on CGO10 impregnated with K2O or BaO
4.4.1 Evolution of surface species over CGO10
When the CGO10 powder sample is exposed to NO (1000 ppm) and O2 (10%), the most
pronounced features of the IR spectra over the entire temperature range from 500 °C to 300 °C,
are two groups of peaks located around 1600 cm -1 and 1200 cm -1 , see Figure 9 and Figure 10. In
between these two features a broad negative peak is observed. This negative peak becomes more
and more negative when the temperature decreases, indicating that adsorbed species are
removed during the experiment. In addition to these peaks several smaller peaks, both negative
and positive, are observed in the range 1900-4000 cm -1 . In general, the peak intensities increases
with decreasing temperature, which indicates that the adsorbed species are more readily
adsorbed at lower temperatures. Some peaks, which are not observed at 500 °C, become visible at
lower temperatures, see Figure 10, which indicates there is a change in the type of adsorbed
species with temperature. With respect to the time dependence of the peaks, no new peaks
appear after the first minute of exposure at each temperature; however the peak intensity tends
to increase with time, most pronounced for the measurement at 500 °C.
Absorbance
1.4
1.2
1.0
0.8
0.6
0.4
0.2
0.0
4000
300 °C
350 °C
400 °C
450 °C
500 °C
3500
3000
Wavenumber [cm-1]
Figure 9. DRIFT spectra recorded on non-impregnated CGO sample in 1000 ppm NO + 10% O2 at
300-500 °C.
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