| In the field of photocatalytic hydrogen production and as a molecular catalyst in the electrocatalytic reduction of CO2,porphyrin plays an important role.Photocatalytic hydrogen production isan apparatus which water will be converted to H2 using semiconductor absorption of solar.The semiconductor are wide band-gap,which only used ultraviolet and near ultraviolet light.Dye sensitization is an important means of extending the spectral response of semiconductors.Porphyrins have a planar conjugated structure,which ehibit intense spectral response bands in the visible light and possess good chemical,photo-,and thermal stability,tunable structure.Therefore,the porphyrin can be used in the photocatalysis as dyes.In addition,metalloporphyrins become the most promising catalysthas a strong ability for electrocatalytic reduction of CO2.The main contents and conclusions obtained are summarized as follows:1.A series of asymmetric zinc porphyrin?ZnPy?derivatives bearing different external substituents were synthesized and used to sensitize Pt-loaded graphitic carbon nitride?Pt/g-C3N4?for photocatalytic H2 production.Among which,ZnPy-1 has one benzoic acidand three phenyls as peripheralsubstituents,while ZnPy-2,ZnPy-3,and ZnPy-4 contain one benzoic acid and three pseudo-pyridineswith different N-atom positions.ZnPy-4-sensitized Pt/g-C3N4?ZnPy-4-Pt/g-C3N4?exhibits the best average H2 production activity of 524 ?mol h-1 with an extremely high turnover number?TON?of 11089 h-1,which is much higher than that?328?mol h-1?of ZnPy-2-Pt/g-C3N4 with a TON of 6942 h-1.The different N-atom positions in the pseudo-pyridines result in different interaction of the ZnPy dyes with the sacrificial reagent,which then strongly influences the photoactivity for H2 production.The present results demonstrate the molecular engineering aspect of ZnPy dyes in which the fine tuning of molecular structures is crucial for improving the photocatalytic H2production activity over the dye-sensitized semiconductor.2.Asymmetric ZnPy-5 and ZnPy-6 porphyrins containing pyrimidine groups as peripheral substituents were designed and synthesized in order to continue to explore the influence of the number of N in the peripheral substituents on the photocatalytic hydrogen production system.ZnPy-6-sensitized Pt/g-C3N4?ZnPy-4-Pt/g-C3N4?exhibits the best average H2 production activity of 524 ?mol h-1 with an extremely high turnover number?TON?of 12381 h-1 during ZnPy-1\?ZnPy-6,which is much higher than that?418?mol h-1?of ZnPy-5-Pt/g-C3N4 with a TON of 8845 h-1.ZnPy-6in the peripheral substituents containing two nitrogens can be more effective and sacrifice agent AA combination to promote the recovery of dyes,and another heteroatom pyrimidine group can better increase the ability of excited state electron transfer.Even in the same position,porphyrins containing two nitrogen atom pyrimidine groups exhibit better hydrogen production relative to porphyrins containing a nitrogen atom pyridine group.Therefore,through the second and third chapters,it is proved that the position and the number of nitrogen atoms in the peripheral substituents have a great influence on the photocatalytic hydrogen production performance.3.In order to further explore the application of nitrogen-containing substituted porphyrins,the design and application of perovalent iron-doped FeP2PyP as a molecular catalyst in the electrocatalytic reduction of CO2 was designed.The results show that FeT2PyP exhibits three distinct redox peaks in N2 atmosphere with tetrabutylhexafluorophosphate?TBANPF6?as supporting electrolyte,and Fe?/?0.54 V,Fen?/??-1.42V?and Fe1/0?-2.01V??vs.Ag/Ag+?,the Fe1/0 reduction peak current value is increased by 3 times in the atmosphere of CO2 relative to the inert N2 atmosphere,The test showed significant electrocatalytic activity.In the N2 atmosphere,the peak current value and the scanning speed show a linear relationship of ip??v1/2?,indicating that the molecular catalyst is controlled by mass transfer and exhibits a quasi-reversible process. |
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