Hydration of Rutile TiO2: Thermodynamics and Effects on n- and p-Type Electronic Conduction

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• 作者：Skjalg Erdal ; Camilla Kongshaug ; Tor S. Bjø ; rheim ; Niina Jalarvo ; Reidar Haugsrud ; Truls Norby
• 刊名：Journal of Physical Chemistry C
• 出版年：2010
• 出版时间：May 20, 2010
• 年：2010
• 卷：114
• 期：19
• 页码：9139-9145
• 全文大小：207K
• 年卷期：v.114,no.19(May 20, 2010)
• ISSN：1932-7455

文摘

The bulk conductivity of polycrystalline 1 mol-% Fe-doped rutile TiO₂ has been measured as a function of p_H2O and temperature under oxidizing and reducing conditions. From the p_H2O-dependency of the conductivity, it is concluded that protons are significant positive defects and, furthermore, that mixed p-type electronic and protonic, and n-type electronic conduction dominate under oxidizing and reducing conditions, respectively. H₂O/D₂O isotope exchange confirmed that protons are significant charge carriers under wet oxidizing conditions below approximately 600 °C. Thermodynamic parameters for the hydration reaction were obtained by modeling the experimental p_H2O and temperature dependencies, assuming that the acceptor dopant (Fe³⁺) is charge compensated by protons and oxygen vacancies, and from ab initio density functional theory (DFT) calculations. The experimental data yield standard enthalpy changes of hydration of −130 ± 16 kJ/mol, whereas the calculated values are somewhat more negative; −155 to −162 kJ/mol. Based on such favorable thermodynamics of hydration, it is concluded that protons will be the dominating positive defect in TiO₂ under most conditions of practical interest.