Prepartion Of Tri-Azo-graphene Hybrids For Photothermal Storage

The azobenzene?azo?chromophone can conduct a photoinduced configuration transformation from a low-energy stable trans-isomer to the high-energy metastable cis-isomer by absorbing specific wavelength rays.And the cis-configuration of azo is spontaneous to reverse to the trans-isomer because of its low thermodynamic stability.Besides the external stimuli?such as light,heating,etc.?could accelerate this shift.Due to the characteristics,azo have a great research prospects in the solar energy storage materials.We can take advantage of these properties of azo to store light energy in chemical bonds and to achieve the energy controlled release by adjusting the extrinsic stimuli.As an energy storage material,it has good reversibility,environmental protection and recycling performance.The inevitable azobenzene and its derivatives have the disadvantages of short half-life,low energy density and poor regulation.In response to these problems,the designed tri-Azo derivatives were synthesized by diazo coupling and amide reaction.Due to its special structure,tri-Azo has the large intramolecular interaction and huge steric hindrance.Taken the reduced graphene oxide?rGO?as a template,grafting the tri-Azo to graphene and improving the grafting density by repeating the diazotization 1-4 times.The tri-Azo exhibit the close-packed and ordered structure,which is conducive to the H-bond between the tri-Azo and greatly improve its?_1/2/2 and energy density.The modified Hunmers method was used to prepare graphene oxide?GO?and to prepare the rGO with good conjugation structure and good dispersibility the sodium borohydride was applied as a reducing agent to control the degree of reduction of GO by controlling the reaction temperature and time.The graft density of the material was calculated by thermogravimetric analyisis?TGA?and X-ray photoelectron spectroscopy?XPS?and the energy densities at different graft densities were measured by differential scanning calorimetry?DSC?and UV-Vis absorption spectra.It can be seen that when the grafting rate is 1/68,the tri-Azo/rGO reached the maximum energy density of 150.3 Wh/kg,and the maximum power density of 3036.6W/kg.UV-Vis absorption spectra and DSC were used to track the isomerization and exotherm of solvents,powders,and films at different heating rates.It was found that the accelerated heating rate facilitates the rapid release of heat but makes the storage heat cannot be fully utilized.The energy density of film relative to the solution and powder is low,but it has a higher application value.Through the infrared thermography track the exothermic process and thermochromic paste visualization demonstrated that the heat of tri-Azo/rGO was given out.Furthermore,the temperature difference?TD?was formed and the DT of over 7?for 40 min when the temperature was above 80?.