Theoretical Study On Physics Key Parameters Of Organic Dyes In Photocatalytic Hydrogen Production

The dyes used in photo-driven catalytic hydrogen production are almost all metal complexes such as ruthenium or iridium,but since these metal elements are rare and the dyes are difficult to synthesize,their development will be limited to some extent.At the same time,organic dyes have attracted wide attention from researchers in recent years due to their low cost,abundant resources and easy synthesis.In a homogeneous light-driven catalytic hydrogen production system,Gueret et al.experimented with a positively charged organic dye?Triazatriangulenium,TATA⁺?,under the same experimental conditions,compared with the benchmark Ru tris-bipyridine.The hydrogen production performance of TATA⁺greatly exceeds the benchmark Ru tris-bipyridine.Because the theoretical calculation of the key parameters of homogeneous light-driven catalytic hydrogen production organic dyes is not accurate enough,some numerical errors are large.In order to obtain theoretical calculation methods that are more in line with the key parameters of the system and more competitive hydrogen-making organic dye molecules,In this thesis,the experimentally synthesized organic dye TATA⁺was studied as follows:?1?In order to obtain a theoretical calculation method that is more compatible with the experimental values,we use the density functional theory?DFT?and time-dependent density functional theory?TDDFT?based on the electrochemical experimental values measured after the organic dye TATA⁺experimental synthesis.The exchange correlation function and basis set used in the optimization of the ground state structure of the organic dye and the calculation of the excited state were tested and screened.Finally,the THCH function and the 6-311G+?d,p?basis set are the most suitable for the experimental values.The overall error is only 1%,which provides a theoretical guarantee for the design of subsequent new organic dye molecules.?2?The novel dye T⁺101-T⁺109 was designed by modifying the side chain ethoxyethanol of the experimentally synthesized TATA⁺dye.Through a series of key parameters of its molecular structure,energy level arrangement,absorption spectrum,redox potential and photoinduced electron transfer free energy,we found that the spectral absorption properties of T⁺103 and T⁺104 dyes were superior,and the reduction potential and photoinduced electron transfer free energy values reached E_red=-1.34 V and?G⁰=-0.77 e V,respectively,which were improved to some extent compared with TATA⁺dyes.The results show that when n-pentylamine and n-heptanol are used as side chains,it will be more beneficial to promote the reduction quenching process,thereby effectively improve the efficiency of photo-driven catalytic hydrogen production.?3?Based on the TATA⁺parent prototype T⁺01 dye,the molecular design of the dye molecular side chain was carried out at the R1 and R2 positions,and obtained a series of organic dyes.By studying their molecular orbital level,absorption spectrum,molar extinction coefficient,photoinduced electron transfer free energy,oxidation potential,and reduction potential,it was finally found that the n-butyl chain in T⁺12 is the best at the R1 and R2 positions.and the maximum absorption peak is 521 nm.The overall coverage of visible light is very good.Compared with TATA⁺,the maximum molar extinction coefficient is increased by 16.1%to 7.735×103 M^-1.cm^-1,and E_red=-1.51 V and?G⁰=-0.93 e V are increased by 24%and 48%,respectively.It is theoretically believed that T⁺12 may be a potentially efficient dye molecule in visible light driven hydrogen production.?4?Based on T⁺12,a series of organic dyes T⁺201-T⁺216 were designed by modifying the triazabenzene ring,among which T⁺205,T⁺210 and T⁺211 may be better visible light driven hydrogen production.The candidate organic dye photosensitizers of the device have E_red values of-1.63,-1.84,and-1.64 V,respectively,and the?G⁰values are-1.31,-2.14,and-1.19 e V,respectively,which is an ideal improvement over T⁺12(E_red=-1.51 V and?G⁰=-0.93 e V).In addition,the maximum absorption peaks of T⁺205 and T⁺210 have a significant red shift compared to T⁺12 and the maximum molar extinction coefficients are 1.0923×10⁴ M^-1.cm^-1 and 1.0317×10⁴M^-1.cm^-1,which is 41.2%and 33.4%higher than T⁺12(7.735×10³ M^-1.cm^-1).