ABSTRACT

The enhancement of surface acidity for tungsten-doped CeTiO_x was investigated through electronic structure. Tungsten doping increased the ratio of Ce³⁺ from 12.0% to 29.6%, which was confirmed by XPS. The doped tungsten was present as W⁵⁺ in a ratio of 71.5%. In O K-edge XAS spectra, increase in $I_{e_g}/I_{t_{2g}}$ indicated the formation of oxygen vacancies through tungsten doping. The decrease in W 5d-e_g peak intensity demonstrated the occupation of the W 5d orbital by electrons formed at the oxygen vacancies. The enrichment of W⁵⁺ was owing to transfer of electrons to 5d-e_g orbital of tungsten rather than to cerium ions. The acid sites were analysed using FTIR and NH₃-TPD. The peak intensity of Brønsted acid sites and amount of NH₃ desorption increased from 66.2 to 136.1 µmol g⁻¹ with tungsten doping. The doped tungsten formed Brønsted acid sites and led to enhanced surface acidity and catalytic activity.

摘要

通过电子结构研究了钨掺杂的 CeTiO _x表面酸性的增强。钨掺杂使 Ce ³⁺的比例从 12.0% 增加到 29.6%，XPS 证实了这一点。掺杂钨以71.5%的比例作为W ⁵⁺存在。在 O K边缘 XAS 光谱中，增加${\mathrm{一世}}_{{\mathrm{电子}}_G}/{\mathrm{一世}}_{{吨}_{2G}}$表明通过钨掺杂形成氧空位。W 5d-e _g峰强度的降低表明在氧空位处形成的电子占据了W 5d 轨道。W ⁵⁺的富集是由于电子转移到钨的5d-e _g轨道而不是铈离子。使用FTIR和NH ₃ -TPD分析酸性位点。随着钨掺杂，Brønsted 酸位的峰值强度和NH ₃解吸量从66.2 增加到136.1 µmol g ^-1。掺杂的钨形成了布朗斯台德酸位点并导致增强的表面酸性和催化活性。