. 2016 May 17;21(5):644. doi: 10.3390/molecules21050644

Table 2.

Surface characteristics (determined by XPS) of Ce-Ln and Cu/Ce-Ln (Ln: Gd, La, Pr, Nd, Sm) materials.

Samples	XPS Atomic Ratios ^a			Relative Concentrations (%) ^c
Samples	Cu/Ce + Ln (0.70) ^b	Ce/Ce + Ln (0.50) ^b	Ln/Ce + Ln (0.50) ^b	Cu⁺	Ce³⁺	O_I	O_I/O_II
CeO₂	-	1	-	-	17.82	50.37	1.01
Cu/CeO₂	0.62	1	-	13.20	18.79	52.02	0.90
Ce-Gd	-	0.04	0.96	-	23.13	19.89	0.25
Cu/Ce-Gd	0.08	0.02	0.98	6.41	18.27	41.14	0.41
Ce-La	-	0.43	0.57	-	20.12	25.34	0.34
Cu/Ce-La	0.29	0.40	0.60	<1	23.53	35.10	0.54
Ce-Pr	-	0.40	0.60	-	20.06	44.93	0.92
Cu/Ce-Pr	0.94	0.59	0.41	^d	20.60	45.01	0.82
Ce-Nd	-	0.21	0.79	-	20.92	27.53	0.37
Cu/Ce-Nd	0.17	0.26	0.74	29.20	22.26	34.30	0.49
Ce-Sm	-	0.34	0.66	-	23.20	28.46	0.40
Cu/Ce-Sm	0.69	0.31	0.69	<1	18.38	41.39	0.63

^a estimated from XPS spectra; ^b calculated from the nominal catalyst composition of 20 wt. % Cu/Ce_0.5Ln_0.5O_1.75; ^c estimated from the integrated areas of the respective XPS peaks; ^d superimposition with the Pr 3d peak.