Photochemical Simple Chemical Reaction Under The Condition Of The Theoretical Calculation Of The Simulation

In the21th century, energy issues are very important. In such a background, a series of new energy plans have been launched. New energy is generally devided into three categories, namely solar, wind and biomass. Solar energy is one of the most promising new energy technologies. The solar energy can be directly converted into electrical energy, namely, photovoltaics. Photovoltaics have very long history, but the basic structure and principles are maintained. Single-layer photovoltaics is simple and stable, but the light conversion efficiency is low. Theoretically limit conversion efficiency of single-layer photovoltaics is33%, while multi-layer photovoltaics is66%. According to the National Renewable Energy Laboratory, the experimental highest conversion efficiency is43.5%. In addition to the traditional photovoltaics, there is another solar cell, called photoelectrochemical cell, which is converting solar energy into chemical energy. Summarily, the basic principles of photovoltaics and photoelectrochemical cell is quite similar. This paper introduces you my theoretical study of photocatalysis. This paper is divided into three parts, the first part is focus on TiO2photocatalytic water splitting (OER); the second one is focus on the morphology and its relationship to OER activity; the third part is the photocatalytic mechanism of the oxidation of alcohols.Mechanism and Activity of Photocatalytic Oxygen Evolution on Titania Anatase in Aqueous Surroundings:Due to its high overpotential and low efficiency, the conversion of water to O2using solar energy remains a bottleneck for photocatalytic water splitting. Here the microscopic mechanisms of the oxygen evolution reaction (OER) on differently structured anatase surfaces in aqueous surroundings, namely,(101),(001), and (102), are determined and compared systematically by combining first-principles density functional theory calculations and a parallel periodic continuum solvation model. We show that OER involves the sequential removal of protons from surface oxidative species, forming surface peroxo and superoxo intermediates. The initiating step, the first proton removal, dictates the high overpotential. Only at an overpotential of0.7V (1.93V vs SHE) does this rate-controlling step become surmountable at room temperature:the free energy change of the step is0.69,0.63, and0.61eV for (101),(102), and (001) surfaces, respectively. We therefore conclude that (i) OER is not sensitive to the local surface structure of anatase and (ii) visible light (<～590nm) is, in principle, capable of driving the photocatatlytic OER on anatase kinetically. By co-doping high-valent elements into the anatase subsurface, we demonstrate that the high overpotential of the OER can be significantly reduced, with extra occupied levels above the valence band.Particle Size, Shape and Activity for Photocatalysis on Titania Anatase Nanoparticles in Aqueous SurroundingsTiO2nanoparticles have been widely utilized in photocatalysis, but the atomic level understanding on their working mechanism falls much short of expectations. In particular, the correlation between the particle structure and the photocatalytic activity is not established yet, although it was observed that the activity is sensitive to the particle size and shape. This work, by investigating a series of TiO2anatase nanoparticles with different size and shape as the photocatalyst for water oxidation, correlates quantitatively the particle size and shape with the photocatalytic activity of the oxygen evolution reaction (OER). Extensive density functional theory (DFT) calculations combined with the periodic continuum solvation model have been utilized to compute the electronic structure of nanoparticles in aqueous solution and provide the reaction energetics for the key elementary reaction. We demonstrate that the equilibriumshape of nanoparticle is sensitive to its size from1to30nm, and the sharp crystals possess much higher activity than the flat crystals in OER, which in combination lead to the morphology dependence of photocatalytic activity. The conventionally regarded quantum size effect is excluded as the major cause. The physical origin for the shape-activity relationship is identified to be the unique spatial separation/localization of the frontier orbitals in the sharp nanoparticles, which benefits the adsorption of the key reaction intermediate (i.e., OH) in OER on the exposed five-coordinated Ti of (101) facet. The theoretical results here provide a firm basis for maximizing photocatalytic activity via nanostructure engineering and are also of significance for understanding photocatalysis on nanomaterials in general.Mechanism and Activity of Photocatalytic Oxidation of Benzyl Alcohol on Titania Anatase:In previous works, we have systematically studied the OER reaction mechanism and the relationship between morphology and photocatalytic reactivity. But these studies are all based on thermodynamics, while the kinetics is ignored. Therefore, our next study is focus on the photocatalytic kinetics. To this end, we chose the photocatalytic oxidation of alcohols as a protype reaction. Experimentally, this process shows a very unique reaction pathway. Our results show that the photocatalytic kinetics is quite dirrerent from other catalysis, e.g. Au, Pt.