Research On The Synthesis Of Cyclic Carbonates And Dye-sensitized Solar Cells Using Metallpoprphyins

Energy and environment are the most important problems in this world. At present, due to the depletion of fossil energy and greenhouse gas emissions, the development of environmentally friendly sustainable energy technologies has become the most urgent strategic objectives for the countries in the world. On the one hand, as a major greenhouse gas, the utilization of carbon dioxide has a significant economic and environmental effect. On the other hand, the dye-sensitized solar cells (DSSC) as a new type of low-cost solar photovoltaic devices, has a very broad prospects in the field of renewable energy utilization.Based on this understanding and considering the photosynthesis of plants in nature, it captures not only the carbon dioxide from the atmosphere, but also the solar energy, from the sun. The key of photosynthesis is the core of magnesiumporpyrin in the chlorophyll. Thus, in this thesis, the metalloporphyrins were choosed as our research objects. We investigate its catalytic effect in the synthesis reaction of CO2and epoxies to cyclic carbonate, and use it as photosensitizer to study the photoelectricity performance of DSSC.In the synthesis reaction of cyclic carbonate, a series of new and highly efficient catalyst of5,10,15,20-tetra(4-carboxyphenyl)porphyrinato cobalt salt (TCPPCo(â…¢)X, X=Cl, Br, OAc, CF3OO) were developed to catalyze the coupling reaction of carbon dioxide and propylene oxide. By comparing the different axial counterions and co-catalyst, we systematically studied the role of TCPPCo(â…¢)X in the coupling reaction of carbon dioxide and propylene oxide. Furthermore, it was discovered that the Br(?)nsted acid can accelerate this reaction. A kinetic study demonstrated that the coupling reaction has lower activation energy with additional organic acid than that without organic acid and follows the rule of first order reaction. This promotion can be attributed to the additional activation of epoxide caused by Bronsted acid. In DSSC research, based on the theory of charge transport and interfacial charge transfer and aimed at directional transmission of the electron, and taking into account the integrity of the cell, the research focused on three aspects of dyes, preparation of the photoelectrode and development of electrolyte. A systematic study of dye-sensitized solar cell performance and the intrinsic charge transport mechanism was carried out, which is benefit for the development of efficient dye-sensitized solar cells.In the synthesis of dyes, we synthesized a series of porphyrin dyes with different metal centers and investigated the effect of central metal for the porphyrin dyes. Due to the unique molecular orbital of the Ru and donator effect of axial ligand triphenylphosphine, the cell sensitized by TCPPRu(â…¡)(PPh3)2had a significantly lager IPCE and light current density than the other metal porphyrin dyes, thus had a enhancement in the performance of dye-sensitized solar cell. This part of the work help us to get a deeper understanding on the mechanism of dye molecules in dye-sensitized solar cells and demonstrated the effect of metal centers, conjugation of molecular structure and electronic directional transmission for the dye, in particular demonstrated the role of the axial coordination of the metal center.In electrode preparation, in order to make better use of the advantages of one-dimensional nanostructures in the electronic transmission and consider the adsorption of the dye, we doped one-dimensional TiO2band into TiO2nanoparticles to form composite semiconductor electrode. Comparing to the cell based on single TiO2nanoparticles electrode, this composite electrode cell obtain a better photoelectric performance. Further, by using electrochemical impedance spectroscopy, the effect for the voltage, the electron diffusion coefficient, electron lifetime and charge collection efficiency of cell are discussed in detail with the introduction of one-dimensional TiO2nanoribbons and the results explained the improvement of one-dimensional TiO2nanobelts for the photoelectric properties of the cell, which confirm again that electronic directional transmission is benefit to improve the performance of DSSC.In the development of electrolyte, based on the idea of electronic directional transmission and the work in literature, we added4-tert-butylpyridine (TBP) and1,2-dimethyl-3-propylimidazolium ions (DMPâ…¡) into electrolyte of cell to form blocking layers. These blocking layers can retard the interfacial reaction of the electron in the surface of TiO2semiconductor electrode with I3-ions in the electrolyte without deteriorating the rate of regeneration of the oxidized dyes molecules, which improve the electric collection efficiency of the TiO2electrode resulting a better performance of DSSC. Further, by linear sweep voltammetry and electrochemical impedance test, we confirmed the formation of the molecular barrier, and intrinsically demonstrated the enhancement in photovoltaic performance of dye-sensitized solar cells arise from the formation of blocking layers.