Wu Longxia, Wang Zhengming, Xiong Feng, Sun Guanghui, Chai Peng, Zhang Zhen, Xu Hong, Fu Cong, Huang Weixin
Hefei National Laboratory for Physical Sciences at Microscale, Key Laboratory of Surface and Interface Chemistry and Energy Catalysis of Anhui Higher Education Institutes, CAS Key Laboratory of Materials for Energy Conversion, Department of Chemical Physics, University of Science and Technology of China, Jinzhai Road 96, Hefei 230026, China.
J Chem Phys. 2020 Jan 31;152(4):044702. doi: 10.1063/1.5135945.
Surface chemistry and photochemistry of small molecules on the rutile TiO(001) and TiO(011)-(2 × 1) surfaces were studied by low energy electron diffraction, thermal desorption spectroscopy, and x-ray photoelectron spectroscopy. It was found that the TiO(001) surface mainly exhibits the defects of Ti interstitials in the near-surface region, while the TiO(011)-(2 × 1) surface mainly exhibits the defects of double-oxygen vacancies. The defect structures of TiO surfaces strongly affect their adsorption and thermal/photodesorption behaviors. On the TiO(001) surface, CHOH and HO dissociatively adsorb at the surface Ti sites near Ti interstitials; O molecularly adsorbs at the surface Ti sites adjacent to Ti interstitials, forming photoactive O species that undergoes a hole-mediated photodesorption process; CO adsorbs at the nearest surface Ti sites close to the Ti interstitials, but CO does not, and the resulting CO species is photoactive; and both CO and CO species adsorbed at the normal Ti sites are photoinactive. On the TiO(011)-(2 × 1) surface, O adsorbs only at the double-oxygen vacancy sites, and the resulting O species dissociates to form two oxygen atoms to refill in the oxygen vacancies upon heating; CO adsorbs at the double-oxygen vacancy sites, but CO does not, and the resulting CO species is photoactive; and both CO and CO species adsorbed at the surface Ti sites are photoinactive. These results broaden the fundamental understandings of the chemistry and photochemistry of TiO surfaces, and the established structure-reactivity relation of small molecules on TiO surfaces is useful in probing complex structures of TiO powder catalysts.
通过低能电子衍射、热脱附光谱和X射线光电子能谱研究了小分子在金红石型TiO(001)和TiO(011)-(2×1)表面的表面化学和光化学。研究发现，TiO(001)表面在近表面区域主要表现为Ti间隙缺陷，而TiO(011)-(2×1)表面主要表现为双氧空位缺陷。TiO表面的缺陷结构强烈影响其吸附和热/光脱附行为。在TiO(001)表面，CHOH和HO在靠近Ti间隙的表面Ti位点发生解离吸附；O分子吸附在与Ti间隙相邻的表面Ti位点，形成光活性O物种，该物种经历空穴介导的光脱附过程；CO吸附在靠近Ti间隙的最近表面Ti位点，但CO不吸附，生成的CO物种具有光活性；吸附在正常Ti位点的CO和CO物种均无光活性。在TiO(011)-(2×1)表面，O仅吸附在双氧空位位点，加热时生成的O物种解离形成两个氧原子以填充氧空位；CO吸附在双氧空位位点，但CO不吸附，生成的CO物种具有光活性；吸附在表面Ti位点的CO和CO物种均无光活性。这些结果拓宽了对TiO表面化学和光化学的基本认识，所建立的TiO表面小分子结构-反应性关系有助于探究TiO粉末催化剂的复杂结构。
