Electrons Stored In Amorphous TiO₂ With Light Radiation And Its Application

Nowadays,the energy consumption is raising,with the demand for energy significantly rising as well.Therefore,people are starting to focus on the solar energy which is rich in the world.Because solar energy cannot be directly applied to production,we must convert solar energy into other forms of energy.For example,solar energy was converted into electricity in solar cells,and solar energy was also converted into chemical energy in semiconductor photocatalytic technology,etc.The process of the conversion of solar energy often involve light carrier generation and directional transmission,especially for the process of photocatalytic,where the photogenerated electron and hole pairs are separated and transferred for the reaction.Therefore,in the process of solar energy utilization,the photogenerated carrier serve as the"intermediate"of energy conversion,which play an important role in the conversion of solar energy to other energy.Recently,researchers have begun to focus on the storage of bare carriers,such as the storage of photogenerated electrons.A series of chemical reactions are carried out in the dark by storing photoelectrons temporarily in the material system and then releasing in the dark state.It is possible to avoid the occurrence of the reverse reaction by temporarily storing the photogenerated electrons in the material system.What^’s more,the subsequent reaction could occur in the dark state,thus expanding the range of solar energy utilization.In the study of storing the photogenerated electrons,heteropoly acid（HPA）,nano-particle metal oxides（TiO₂,ZnO,etc.）and amorphous oxides have been found to possess the properties of storing the photogenerated electrons.And in the process of research,it is found that when material possesses the electrons stored in the light,it will display three distinct characteristics:first,the liquid full of electrons is blue;secondly,the liquid has obvious absorption peaks at 400-800nm in UV-Vis spectrum;thirdly,the active site of storing electrons can be detected by ESR.According to the above three characteristics,it is found that amorphous TiO₂ has the properties of optical storage electron.A series of studies were carried out to investigate the properties of storing the photogenerated electrons and the application of the electrons in production of H₂ and hydrogenation of cinnamaldehyde.The main results were as follows:（1）With ethylene glycol titanium（TG）as the precursor,and through a simple light radiation,we prepared amorphous TiO₂ possessing porous structure.Further,with the ethylene glycol as hole trapping agent,we found that amorphous TiO₂ possess the properties of storing the photogenerated electrons under anaerobic conditions.By using K₂Cr₂O₇ solution as the titrant,the amount of photoelectron stored in 20 mg of TiO₂was measured as 22.6μmol after 1 h light radiation.In addition,when different alcohols were used as cavitation agents,ethylene glycol was found to be the best hole capture agent for the storage of photogenerated electrons.（2）After study,we found that protons were also stored on the amorphous TiO₂,for the sake of the stability of the electrons stored on the amorphous TiO₂.And H₂ was produced with the catalysis of MoS₂ by proton-coupled electron transfer（PCET）to the surface of MoS₂.The conversion rate of electrons stored on the amorphous TiO₂ to H₂is as high as 80%,and the efficiency remain unchanged with the increment of electrons stored on the amorphous TiO₂.（3）The stored electrons can also reduce cinnamaldehyde to benzenepropanal in ethanol,and the conversion rate of cinnamaldehyde is up to 94.7%,and the conversion rate of the stored electrons is 72.3%.Moreover,after adding water to the solvent,cinnamyl alcohol would appear as the product of the reduction process,and the addition of KOH can accelerate the reduction rate of cinnamaldehyde,also improving the selectivity of cinnamic alcohol.