Construction And Properties Of Organic Photothermal Materials Based On Fusion Donor-acceptor Structure

The dilemma of the shortage of fossil energy resources and the scarcity of fresh water resources severely restricts the development of human society.The search for alternative energy to solve the freshwater crisis has aroused extensive attention and research.Solar energy,as a clean and renewable energy,has become a hot topic in human research.In recent years,organic small molecule photothermal materials have shown great application potential in solar hydropower co-generation.However,the low efficiency of solar thermal conversion limits its application.A planar fusion donor-acceptor（D-A）organic photothermal material（DDHT）and solar energy evaporator（DDHT/wood）are designed in this paper.The main research content of this paper is divided into the following three aspects:（1）Construction and physicochemical properties of organic photothermal materials with fused electron donor-acceptor structuresThe unsatisfactory optical stability and narrow optical absorption range limit the application of polycyclicπ-conjugated organic small molecule compounds as photothermal materials Therefore,it is still challenging to develop polycyclicπ-conjugated compounds with wide absorption spectra and good photostability.In this study,a planar donor-acceptor（D-A）organic photothermal material（DDHT）with excellent photothermal properties was designed by fusing a strongly electron-donating arylamine unit and strongly electron-withdrawing quinoxalino[2,3-a]phenazine unit.The D-A structure of the fusion ring not only makes the material through the low energy intramolecular charge transfer transition,resulting in the spectrum redshift,so that the material has a wide absorption spectrum,but also the planar structure and the conjugated plane part has a small steric hindrance,resulting in high efficiencyπ-πstacking between molecules.It has strong face-to-face intermolecularπ-πinteraction and strongly quenched fluorescence through intermolecular energy capture exciton interaction,thus enhancing thermal generation by non-radiative transition.The photothermal conversion efficiency is 58.58%under655 nm laser irradiation and 13.7%under 1.0 k W m^-2 sunlight irradiation,which shows superior photothermal performance.（2）Research on the preparation and performance of solar evaporation system based on DDHTA solar evaporator with good photothermal performance,photothermal stability and fast water transfer was constructed by loading DDHT in natural basswood pieces.DDHT/wood composites exhibit extensive absorption in the 300-950 nm region.The thermal conductivity of DDHT/wood is 0.0550 W m^-1 K^-1,and the temperature of DDHT/wood can reach 53.0℃under1.0 k W m^-2 sunlight irradiation,which indicates that DDHT/wood has a wide range of light absorption,good photothermal conversion performance and thermal insulation ability.In the practical water evaporation application under 1.0 k W m^-2 sunlight irradiation,the evaporation rate is 1.13 kg m^-2 h^-1,and the evaporation efficiency is 78.4%,which can stably evaporate water for a long time.In the real seawater environment,it can be used for long-term stable and effective desalination of seawater,and the desalination effect is remarkable.（3）Research on the integrated properties of DDHT/wood solar evaporatorsBased on the excellent photothermal performance of DDHT,this paper prevents heat energy waste caused by evaporation engineering.DDHT is applied to Seebeck effect based thermoelectric power generation device to produce electric energy.It reached 90.3,145.9 and179.5 m V respectively at 1.0,2.0 and 5.0 k W m^-2 under simulated sunlight.On this basis,this paper designs an integrated synchronous device of water evaporation and thermoelectric conversion,which can produce fresh water and stable electric energy at the same time.Under simulated sunlight of 1.0 k W m^-2,the evaporation rate of water is 0.77 kg m^-2 h^-1,and the efficiency is 52.3%.Using waste heat to generate thermoelectricity,the maximum voltage is 45.6.It has realized the parallel production of water evaporation and power generation,providing a new solution to solve energy shortage and fresh water crisis.