# Supplementary Material (ESI) for Chemical Communications
# This journal is © The Royal Society of Chemistry 2003
B308321G: Supplementary material: XRD data for the fresh and aged PdCZ samples
Full XRD spectra were measured in the range 20-80°2. Their examination revealed no appreciable
structural difference in the Ce0.68Zr0.32O2 phase in the two aged samples as reported in Table 1. No
evidence for incorporation of Pd in the CZ lattice1 could be found: a cell parameter of 0.5331 nm
corresponding to d(111) = 0.3078 nm can be calculated for Ce0.68Zr0.32O2 upon application of
Vegard law,2,3 which is fully consistent with the experimental data.
Table 1. Structural parameters and particle sizes for the Ce0.68Zr0.32O2 phase.
Sample
PdCZ Aged-ox
PdCZ Aged-Cyc
2 (±0.02)
28.99
29.01
d(111) (nm)
0.3080
0.3078
ps (nm)
16
15
To analyse the nature of the Pd-containing phases, XRD spectra of the PdCZ Fresh, PdCZ AgedOx, and PdCZ Aged-Cyc were collected in the region 35-45° (2) (Fig. 1s). In the inset the results
of fitting of the peaks is shown. Due to the low Pd loading poor signal-to-noise ratio was observed.
No evidence for metallic Pd phase is seen in Fig 1s, spectrum a, suggesting a high Pd dispersion.
However, PdO presents two intense peaks at 31.7 and 45.6° (2 that are superimposed to peaks due
to Ce0.68Zr0.32O2 which would prevent its detection with the present Pd loading.
Upon ageing, evidence for very weak peak/peaks located in the region 35-45° (2) are found (Fig.
1s). Parameters obtained from peak fitting are reported in Table 2, together with the particle sizes as
calculated from the Schrerer formula.
Table 2. Parameters for the peaks reported in Fig. 1s.
d(111) (nm)
ps (nm)
A/Acz(111) x 1000a
2 (±0.02)
38.98
0.2311
30
3.8
39.09
0.2304
42
6.5
40.05
0.2251
18
2.1
a
ratio of integral intensity of the peak to the integrated intensity of the d(111) of the Ce0.68Zr0.32O2
solid solution.
Sample
PdCZ fresh
PdCZ Aged-Ox
PdCZ Aged-Cyc
Metallic Pd presents a peak at d(111) at 40.15° (2), which allows the attribution of the minor peak
observed in Fig. 1s, spectrum c, to the presence of some metal Pd in the PdCZ Aged-Cyc. As for the
peaks observed at 38.98 and 39.09 for, respectively, PdCZ Aged-Ox and PdCZ Aged-Cyc, a
possible attribution of these peaks could be due to the presence of interstitial impurities in the Pd
phase, as previously reported for Pd heated in a hydrocarbon mixture, where the presence of
interstitial carbon caused shift of the d(111) reflection towards lower angles (2) due to lattice
expansion.4 However, the presence of interstitial or substitutional (oxygen in a special position)
oxygen defects would lead to the same modification of the XRD pattern. Consistently with such an
interpretation, PdO and Pd domains were shown to co-exist upon cooling in air of supported Pd
particles due to partial re-oxidation of the metal.5 The absence of Pd particles in the PdCZ Aged-Ox
is, in fact, consistent with different degree of re-oxidation upon cooling of the sample under the
different atmospheres. It should be noted that PdCZ Aged-Ox features somewhat higher surface
concentration of detectable Pd when normalised to Ce0.68Zr0.32O2 phase and particle size compared
to Aged-Cyc.
Therefore, keeping present that both samples were reduced in H2 at 300°C before the catalytic and
other measurements, the present supplementary data confirm a substantial equivalence of the Pd
phase before the activity measurement, even though the different particle sizes do indicate the
occurrence of somewhat higher dispersion of the Pd phase in the PdCZ Aged-Ox compared to
PdCZ Aged-Cyc.
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# Supplementary Material (ESI) for Chemical Communications
# This journal is © The Royal Society of Chemistry 2003
Fig. 1s. Powder XRD patterns of (a) PdCZ fresh, (b) PdCZ Aged-Ox and (c) PdCZ Aged-Cyc
samples.
12
a
10
counts
8
6
4
2
0
35
36
37
38
39
40
41
42
43
44
45

3
b
2.5
counts
2
1.5
counts
1
0.5
0
37
38
39
40
41
42
2theta
35
36
37
38
39
40
41
42
43
44
45

5
4
c
counts
3
2
1
0
counts
38
38.5
39
39.5
40
40.5
41
-1
-2
2theta
35
36
37
38
39
40
41
42
43
44
45

References
1. A. Primavera, A. Trovarelli, C. de Leitenburg, G. Dolcetti and J. Llorca, Stud. Surf. Sci. Catal.
1998, 119, 87.
2. M. Yashima, N. Ishizawa and M. Yoshimura, J. Amer. Ceram. Soc. 1992, 75, 1541.
3. M. Yashima, N. Ishizawa and M. Yoshimura, J. Amer. Ceram. Soc. 1992, 75, 1550.
4. S. B. Ziemecki and J. A. Jones, J. Catal. 1985, 95, 621.
5. A. K. Datye, J. Bravo, T. R. Nelson, P. Atanasova, M. Lyubovsky and L. Pfefferle, Appl. Catal.
A Gen. 2000, 198, 179.
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