Characterization of CuO–ZnO catalysts by X‐ray photoelectron spectroscopy: Precursors, calcined and reduced samples

Abstract

X-ray photoelectron spectroscopy was applied to chracterize CuO-ZnO catalysts (Cu/Zn ataomic ratio ≥1) prepared by thermal decomposition at 350°C in air of hydroxycarbonate precursors obtained by the coprecipitation method at constant pH. For the precursors, the surface Cu/Zn atomic ratios have, within experimental error, the same values as that obtained by chemical analysis. This shows both a homogeneous dispersion of zinc in the zincian-malachite solid solutions for the samples Cu/Zn=92/8, 85/15 and 77/23, and a good interdispersion of the zincian-malachit and aurichalcite phases in the 67/33 and 50/50 samples. In our calcined samples we find a strong interaction between the small oxide particules but no evidence of Cu2+/ZnO and Zn2+/CuO solid solutions. In the catalysts with low zinc loading, the ZnO phase (amorphous or with particles of a size <40 angstrom) tends to cover the CuO particles. The catalysts with high zinc loading present the differential charging phenomenon due to the peculiar morphological situation of CuO and ZnO particles, as shown by the XPS measurements of samples supported on a biased sample holder. The reduction in situ underH2 at 135 and 200°C of these catalysts shows that Cu and Cu+ (Cu2O-like) species are formed

Physico-Chemical and Catalytic Properties of Mesoporous CuO-ZrO2 Catalysts

“…Therefore, the low energy XPS peak observed at 932.2 eV could be assigned to Cu + species which are interacted with ZrO2. It is interesting to note that Moretti et al [42] assigned lower BE values for interactive Cu species and they Deconvolution of Cu 2p 3/2 XP peaks suggests the presence of two kinds of Cu species in their chemical environments. From the curve fitting, the binding energies (BE) of the two Cu 2p 3/2 components at two different BE (932.2 eV and 935.2 eV) were obtained.…”

“…Therefore, the low energy XPS peak observed at 932.2 eV could be assigned to Cu + species which are interacted with ZrO 2 . It is interesting to note that Moretti et al [42] assigned lower BE values for interactive Cu species and they explained that the reason for that is the formation of more covalent Cu-O bond due to strong interaction between CuO and ZnO. These observations lead to the fact that CuO and ZrO 2 in CuZr samples are not a physical mixture, but a chemical interaction existed between them.…”

Efficient Conversion of Maltose into Sorbitol over Magnetic Catalyst in Extremely Low Acid

“…The binding energies (BE) of Cu 2p 3/2 and 2p 1/2 were around 932.3 and 953.2 eV, respectively, which were very close to that of Cu 0 . Note that the binding energies of metallic Cu are around 932.6 and 953.8 eV (Moretti et al 1989;Strohmeier et al 1985). For the Ni element, the obtained binding energies were around 852.8 and 869.9 eV, demonstrating the presence of Ni 2p 3/2 and 2p 1/2 , respectively.…”

An XPS study of the reduction process of CuO–ZnO–Al2O3 catalysts obtained from hydroxycarbonate precursors

“…Details about the XPS apparatus, sample handling and data analysis are reported elsewhere. 4 Briefly, the samples were gently ground in an agate mortar to expose clean surfaces and then pressed in a grooved tantalum sample holder that can be heated resistively. In order to avoid X-ray-induced reduction of the Cu(II) species, the Al anode was operated at low power (12 KV and 10 mA).…”

“…3 We have previously studied by XPS the reduction process of the binary CuO/ZnO system. 4 In this work, we extend our XPS study to the ternary CuO/ZnO/Al 2 O 3 catalysts, investigating in particular the Ł Correspondence to: G. Moretti, Department of Chemistry, University of Rome 'La Sapienza', Piazzale A. Moro 5, 00185 Roma, Italy. E-mail: giuliano.moretti@uniroma1.it effect of the aluminium-containing phase(s) in the reduction process of CuO and in the stabilization of the Cu metal particles.…”