Preparation And Application Of Azobenzene/Three-dimensional Carbon Molecular Energy Storage Materials

With the proposal of"carbon peak"and"carbon neutral"goals,the development and utilization of new energy materials has become an inevitable trend in today's social development.Among many new energy materials,molecular energy storage materials,especially photosensitive molecules,have received extensive attention from scientists.Based on their own photoisomerization characteristics,photosensitive molecules can carry out photothermal storage,and the stored energy is only converted between the environment and itself,which is environmentally friendly and clean.However,its disadvantages such as short storage time and poor energy storage performance limit its application in many fields.In view of the above problems,based on template assembly and molecular engineering,three-dimensional carbon nanocomposites were used as templates to prepare azobenzene/three-dimensional carbon molecular energy storage materials with high grafting density by covalent bonding.By enhancing intermolecular interactions(especially hydrogen bonds),steric hindrance and synergy,the energy storage characteristics and service life are regulated.On this basis,polyvinyl alcohol/azobenzene/three-dimensional carbon flexible film was prepared with trace polyvinyl alcohol as the binder,and a photothermal controllable encoder/decoder was designed by combining the flexible film with the best macroscopic heat release effect with the thermochromic dye.The specific work is as follows:(1)Graphene oxide(GO)was prepared by improved Hummers method;Short multiwalled carbon nanotubes(SCNT)were prepared by hydrochloric acid purification and mixed acid oxidation.Three-dimensional carbon nanocomposites(RGO-SCNT)were prepared by solution self-assembly and controlled reduction of sodium borohydride(NaBH₄)with mass ratios of 1:3,1:1 and 3:1.The results showed that RGO-SCNT with different three-dimensional structures with conjugated structure and water dispersibility were successfully prepared.(2)Azobenzene molecule(AZO)with push-pull electronic structure was synthesized by diazonium salt method,and then AZO was covalently grafted onto the surface of RGO-SCNT with different structures by triple diazonium salt free radical method to prepare azobenzene/three-dimensional carbon molecular energy storage material(AZO/RGO-SCNT).X-ray photoelectron spectroscopy showed that the grafting density of AZO/RGO-SCNT_3:1was the highest,with an average of 16 carbon atoms bonding one AZO(1:15.9).Under high grafting density,the photo-thermal storage performance of molecular energy storage materials was improved through intermolecular interaction(especially hydrogen bond),steric hindrance and the synergistic effect of RGO-SCNT.UV-visible absorption spectroscopy and differential scanning calorimetry proved that the three molecular energy storage materials have excellent cycle stability and reversible photothermal storage performance.Among them,AZO/RGO-SCNT_3:1 has the best photothermal storage performance,and its half-life is 892h,which is 3orders of magnitude higher than AZO(6.5h).The energy density is 119.58Wh/kg,which is195.11%higher than AZO.In addition,its power density is 478W/kg.It is expected to be an ideal photothermal storage material due to its excellent photothermal storage performance.(3)On the basis of the above materials,polyvinyl alcohol/azobenzene/three-dimensional carbon flexible film(PVA/AZO/RGO-SCNT)was prepared by solution self-assembly method and self-support method using trace polyvinyl alcohol(PVA)as binder.The results show that all the three kinds of flexible films are flexible.Among them,PVA/AZO/RGO-SCNT_3:1 has the best energy storage performance and macroscopic heat release effect,and its energy density and power density are 63.57Wh/kg-268.6W/kg.Compared with powder,they still maintain 53.16%-56.19%.The maximum temperature difference is 10.8?,and it still maintains good heat release effect at 50?,60?and 70?.Therefore,a photothermal controllable encoder/decoder was designed by combining PVA/AZO/RGO-SCNT_3:1 with thermochromic dye.This encoder/decoder has strong confidentiality and good repeatability,which provides an important reference for the application of molecular energy storage materials in new coding/decoding fields.