Preparation Of Photoisomerized Materials Based On Azobenzene And Their Energy Storage Performance

With the emergence of energy crisis,energy storage materials have gradually become a research focus.Due to its excellent photoisomerization characteristics,photoisomerized materials based on azobenzene have good application prospects in molecular solar energy storage.It has become an important content to expand its practical application to study the energy storage characteristics of photoisomerized materials based on azobenzene through various synthesis and analysis methods.However,the low energy capacity and short half-lifetime(or energy storage time)have greatly limitted their utilization in high energy and long-term solar energy storage applications.In this dissertation,high-performance photoisomerized materials have been developed based on molecular engineering and templating,which effectively increase the energy density and energy storage time,and provide experimental and theoretical basis for its further application in the field of energy storage..1.Based on the molecular design,a variety of azobenzene derivatives(AZO-1～AZO-4)were synthesized by the diazonium coupling reaction and the acyl chloride-esterification reaction.UV-visible absorption spectra and thermal weight loss curves show that the AZO-1～AZO-4 have excellent properties,such as photoisomerization characteristics,cycle stability and thermal stability.It was also shown that long carbon chain azobenzenes(AZO-2～AZO-4)have a long half-lifetime(64-147 h).2.Using the concept of molecular engineering,a long-chain azobenzene/tetradecanol composite material was prepared by a simple method.The supercooling degree was introduced into the organic phase change material system and the energy storage could be controlled by light.The results show that the composite has good photoisomerization characteristics.It was found that the morphology of the composite material changed from irregular shape to regular spherical shape through irradiation.By adjusting the doping content of long carbon chain azobenzene in composites and the rate of melting/cooling,the supercooling degree of composite material was further optimized before and after irradiation.When the doping content of the long carbon chain azobenzene is 55 wt%and the cooling rate is 20℃ min-1,the supercooling degree of 7.67℃ is reached,and the liquid phase can be maintained under the crystallization temperature of tetradecanol for 10 h.The result of differential scanning calorimetry shows that the total energy density of the composite materials is 66.51 Wh kg-1,which is 126.79%higher than the isomerization enthalpy of the long carbon chain AZO-3.3.A long carbon azobenzene/dodecanoic acid composite material was prepared,and the effects of adjusting the length of the long carbon chain and doping amount of the azobenzene molecule on the performance were studied.The results show that the composite material has good photoisomerization characteristics,and maintains the liquid phase for 10 h at a temperature below the crystallization temperature of dodecanoic acid,and the all energy density of the composite material reaches 58.51 Wh kg-1,which is 90.51%higher than that of the corresponding long carbon chain azobenzene.In addition,it is found that when the length of the carbon chain is 11 alkyl groups(AZO-2)and the doping content is 55 wt%,the supercooling degree can be as high as 12℃,and the phase transition temperature of the composite material was reduced to 25℃,which is conducive to long-term energy storage at room temperature.4.A push-pull electronic structure azobenzene/single-walled carbon nanotube hybrid material/film was synthesized using direct Friedel-crafts acylation reaction using carbon nanotube template.The results of thermal weight loss and X-ray photoelectron spectroscopy showed that the graft density of the hybrid material reached an average of one azobenzene per 31 carbon atoms(1:31).Under high grafting density,the energy density and half-lifetime of the material can be improved through the binding effect and intermolecular interaction.The results show that the energy density of the hybrid material is 80.7 Wh kg-1,which is 106.9%higher than the energy density of azobenzene molecules,and its half-lifetime is 16 h,which is two orders of magnitude higher than that of azobenzene molecules(150 s).In addition,its power density is 292 W kg-1.Infrared imagers showed that a temperature difference between irradiated and unirradiated films is as high as 10℃.At the same time,the hybrid materials and films maintain excellent cycle stability with almost no attenuation under limited cycles,and are expected to achieve high-energy and long-term solar storage and application.