Surface atomic composition of fresh and used samples by XPS analysis.

Sample	Fresh				Used
	Ce/Zr	M/(Ce + Zr)	K/(Ce + Zr)	Ce3+/Ce4+	Ce/Zr	M/(Ce + Zr)	K/(Ce + Zr)	Ce3+/Ce4+
CeZr	1.84			0.24	2.80			0.30
Fe-CeZr	2.46	0.31		0.31	1.93	0.28		0.73
Mn-CeZr	2.29	0.32		0.59	1.36	0.26		0.44
Cu-CeZr	2.73	0.60		0.70	1.41	0.47		0.39
K-CeZr	2.86		0.15	0.36	2.70		0.06	0.41
K-Fe-CeZr	3.92	0.30	0.06	0.55	2.17	0.40	0.15	0.58
K-Cu-CeZr	2.48	0.08	0.14	0.53	1.43	0.37	0.35	1.01