Study On The Synthesis Of New Dyes And Their Applications In DSSCS And CO₂ Reduction

To date,ten terawatts?TW?per year of energy is consumed,and the consumption will increase to 30 TW at 2050.The extra 20 TW of non-CO₂ energy would be compensated by renewable energy to stabilize the concentration of carbon dioxide in the atmosphere.Therefore,a series of research on renewable energy sources has been launched because of seeking the balance between the increasing energy demanding and climate changes during the last decades.Solar energy is regarded as the most prospective energy resource on account of inexhaustibility and Zero-Pollution character.Photoelectric conversion and photochemical conversion are the main forms of solar energy utilization.Dye-sensitized solar cells?DSSCs?,regarded as one of the most promising next-generation solar cells,have attracted intense investigation because of their high solar light-to-electricity conversion efficiency,colorful and decorative nature,their low-cost production,ease of fabrication.In addition,the alliance application of carbon dioxide reduction and sensitized TiO₂ to obtain high-energy compounds was solar photochemical transformation.In the light conversion system,the sensitizer absorbs sunlight and causes the initial electron transfer reaction,which is the key part of the whole system.It is very important for the solar energy conversion to synthesize the choiceness sensitizers.In this paper,the new photosensitizers were synthesized,and then applied in the artificial utilization of solar energy.?1?A series of symmetric SalenZn based dyes with triphenylamine derivatives as the donor,benzoic acid as the acceptor,and coplanar Salen complexes as the spacer have been designed and synthesized for dye-sensitized solar cells.When the tail length of the alkyl substituents is increased from C-0 to C-8 on the donor part,the efficiency of ts DSSC augments evidently.It is found that the incorporation of biscarboxyl groups nstead of the single carboxyl group as anchoring groups induces a remarkableenhancement of the electron injection efficiency from the excited dyes to the TiO₂ semiconductor while generates higher electron density and voltage.?2?For the sensitizers,it is necessary to synthesize the asymmetric Salen type compound in order to ensure the direction of electron transfer in molecular inner.Unsymmetric SalenZn complexes have been designed,synthesized,and wellcharacterized.The performances of their sensitized solar cells have been investigated by optical,photovoltaic,and electrochemical methods.The D-?-A dyes with asymmetrical structures can obtain a unidirectional flow of electrons as well as a good electrnic coupling between the dye and TiO₂.?3?Porphyrin and its derivatives are widely found in biological and energy transfer related to the important organelle.In the previous work,the porphyrin zinc was used in the dye sensitized solar cell by the bionic chlorophyll II.The performances of their sensitized solar cells have been investigated by optical,photovoltaic,and electrochemical methods.The photoelectric conversion efficiency of the solar cells sensitized by the dye with salicylic acid as an anchoring group demonstrated an obvious enhancement when compared with that sensitized by the dye with carboxylic acid as an anchoring group.The density functional theory calculations and the electrochemical impedance spectroscopies revealed that tridentate binding modes could increase the efficiency of electron injection from dyes to the TiO₂ nanoparticles by more electron transmission channel.?4?Aritifical photosynthesis is another way of solar energy utilization.It would manipula solar energy and greenhouse gas degradation to achieve a unified implementation.In this chapter,we constructed an artificial photosynthetic system to be the coupling of water splitting and CO₂ reduction.Through a photoanode CoPi/W:BiVO4 as PSII and a photocathode of NRx@TiO₂ functionalized by Nile reds via covalent linkage or Pd/NRx@TiO₂ with additional palladium nanoparticle as PSI,simulation of leaves photosynthesis system,carbon dioxide is reduced to carbon-based fuels.Methanol and oxygen are the products that can be detected in liquid and gas phase.The main active species in this artificial photosynthesis system are proved by EPR to be hydroxy radicals releasing O₂ gas via H2O₂.Moreover,the carbon source of methanol is validated by 13CO₂ labeling experiment;the 18O₂ is determined by GC-MS coming from H2O18.