在电子激发过程中,在TiO2的表面上发生电子介导的CO氧化
1Department of Chemistry, University of Virginia, Charlottesville, Virginia 22904, USA.
Journal of the American Chemical Society
|September 3, 2010
概括
研究电子激发的一氧化碳 (CO) 在二氧化 (TiO2) 上的氧化,这项研究揭示了电子介导CO2生产. 相比之下,孔驱动氧 (O2) 脱吸,澄清了TiO2表面的反应机制.
科学领域:
- 表面化学 表面化学
- 光催化作用的光催化
- 材料科学 材料科学 材料科学
背景情况:
- 了解TiO2表面上吸附的CO的反应机制对于光催化是至关重要的.
- 电子和孔在半导体材料表面反应中的作用尚未完全阐明.
研究的目的:
- 调查电子和孔在TiO2上吸附的CO的电子激发氧化中的不同作用.
- 通过吸附像Cl2或O2.2这样的电子受体来调整表面电子和孔的可用性.
主要方法:
- 使用TiO2(110) 作为模型表面.
- 吸附Cl2或O2以改变表面电子特性.
- 研究在电子刺激下对CO氧化和O2脱吸的影响.
主要成果:
- 电子受体 (Cl2,O2) 的吸附导致带向上曲,增加孔的可用性和减少电子的可用性.
- 在电子激发过程中观察到增强的O2脱吸和压抑的CO2产生.
- 提供了电子介导的二氧化碳产生和孔介导的二氧化碳脱吸的明确证据.
结论:
- 电子激发的CO氧化在TiO2上 ((110) 主要是一种电子介导的过程.
- 在电子刺激下氧气脱吸是一种通过孔介导的过程.
- 这项研究区分了TiO2表面上的不同反应路径的电荷载体动态.
更多相关视频
相关概念视频
01:26Thermal and Photochemical Electrocyclic Reactions: Overview
Electrocyclic reactions are reversible reactions. They involve an intramolecular cyclization or ring-opening of a conjugated polyene. Shown below are two examples of electrocyclic reactions. In the first reaction, the formation of the cyclic product is favored. In contrast, in the second reaction, ring-opening is favored due to the high ring strain associated with cyclobutene formation.
01:26Photochemical Electrocyclic Reactions: Stereochemistry
The absorption of UV–visible light by conjugated systems causes the promotion of an electron from the ground state to the excited state. Consequently, photochemical electrocyclic reactions proceed via the excited-state HOMO rather than the ground-state HOMO. Since the ground- and excited-state HOMOs have different symmetries, the stereochemical outcome of electrocyclic reactions depends on the mode of activation; i.e., thermal or photochemical.
Selection Rules: Photochemical Activation
Selection Rules: Photochemical Activation
01:22Heterogeneous Catalysis
Heterogeneous catalysis involves a catalyst in a different phase from the reactants. It is a process where the catalyst and the reactants are in distinct phases, typically solid and gas or liquid.Most heterogeneous catalysts are metals, metal oxides, or acids. The list includes transition metals like iron (Fe), cobalt (Co), nickel (Ni), palladium (Pd), platinum (Pt), chromium (Cr), manganese (Mn), tungsten (W), silver (Ag), and copper (Cu). These metals possess partially vacant d orbitals that...
01:43Electron Transport Chain: Complex III and IV
During the electron transport chain, electrons from NADH and FADH2 are first transferred to complexes I and II, respectively. These two complexes then transfer the electrons to ubiquinol, which carries them further to complex III. Complex III passes the electrons across the intermembrane space to Cyt c, which carries them further to complex IV. Complex IV donates electrons to oxygen and reduces it to water. As electrons pass through complexes I, III, and IV, the energy released aids the pumping...
01:12Cycloaddition Reactions: MO Requirements for Photochemical Activation
Some cycloaddition reactions are activated by heat, while others are initiated by light. For example, a [2 + 2] cycloaddition between two ethylene molecules occurs only in the presence of light. It is photochemically allowed but thermally forbidden.
01:46Electron Transport Chain: Complex I and II
The mitochondrial electron transport chain (ETC) is the main energy generation system in the eukaryotic cells. However, mitochondria also produce cytotoxic reactive oxygen species (ROS) due to the large electron flow during oxidative phosphorylation. While Complex I is one of the primary sources of superoxide radicals, ROS production by Complex II is uncommon and may only be observed in cancer cells with mutated complexes.
ROS generation is regulated and maintained at moderate levels necessary...
ROS generation is regulated and maintained at moderate levels necessary...