Multivalence Charge Transfer in Doped and Codoped Photocatalytic TiO2

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• 作者：Hangjuan Ren ; Pramod Koshy ; Fuyang Cao ; Charles Christopher Sorrell
• 刊名：Inorganic Chemistry
• 出版年：2016
• 出版时间：August 15, 2016
• 年：2016
• 卷：55
• 期：16
• 页码：8071-8081
• 全文大小：674K
• 年卷期：0
• ISSN：1520-510X

文摘

The present work reports data for the mineralogical and chemical properties of anatase thin films individually doped or codoped with chromium and vanadium, fabricated by sol–gel spin coating on glass substrates and annealing at 450 °C for 2 h. X-ray photoelectron spectroscopy data indicated the presence of Ti⁴⁺, Ti³⁺, Cr³⁺, and possibly Cr⁴⁺ in the Cr-doped thin films; Ti⁴⁺, Ti³⁺, V³⁺, V⁴⁺, and possibly V⁵⁺ in the V-doped thin films; and Ti⁴⁺, Ti³⁺, Cr³⁺, Cr⁴⁺, V³⁺, V⁴⁺, and possibly V⁵⁺ in the codoped thin films. While the thermodynamically stable valences Ti⁴⁺, Cr³⁺, and V⁵⁺ would be expected to have formed, the presence of the nonequilibrium valences Ti³⁺, Cr⁴⁺, V³⁺, and V⁴⁺ is considered to have resulted from intervalence charge transfer for the Cr-doped and V-doped systems but from multivalence charge transfer (MVCT) for the codoped system. The latter phenomenon, which is introduced as a new conceptual term, describes the nature of the mutual exchange of electrons during valence changes of both dopant (Cr, V) and matrix (Ti) ions during annealing. In the present case, MVCT appears to be a transient metastable condition that acts during annealing, but subsequent UV irradiation can alter its effects.