Preparation And Solar Photothermal Conversion Performance Of Metal Oxide Based Composite Materials

In recent years,the new emerging solar-driven water evaporation technology not only provides a new technical scheme for the efficient utilization of solar energy,but also provides a new way to expand the utilization of solar energy and realize the conversion of solar energy and multiple energy sources.The key of the realization of high efficient solar photothermal conversion is the preparation of photothermal conversion materials with strong absorption in the range of solar spectrum and favourable photothermal conversion ability.Among all solar photothermal materials,the metal oxides materials are considered as one of the most promising materials for high efficiecnt solar-driven water evaporation due to its absorption spectrum matched to solar and adjustable performances.However,becasuse the powdered metal oxide is difficult to be applied to the interface evaporation and the improper design of evaporation device,there are generally low evaporation performance and high cost of metal oxide based photothermal conversion materials.To address these problems,this dissertation innovatively proposes to compound metal oxides with different substrates.By means of the optimization of raw material selection and preparation process,combined with the interface evaporation device,the high-efficiency solar photothermal driven water evaporation under low light intensity is realized.In addition,based on the similar characteristics of solar photothermal conversion materials and super capacitor electrode materials,the innovative proposal of combining super capacitor and solar photothermal interface evaporation enriches the application field of solar photothermal conversion driven water evaporation technology.The main contents of this dissertation are as follows:The Co₃O₄/foam nickel photo thermal conversion material was prepared by hydrothermal calcination two step method.By adjusting the hydrothermal reaction temperature,the Co₃O₄ absorption layer with nano flower and nanowire combination morphology was obtained at 110?,and the maximum absorption rate was 96.27%.Benefited from its good light absorption capacity,the evaporation rate of the composite material can reach 1.226 kg m^-2 h^-1 and the light heat conversion efficiency can reach84.45%under the light intensity of 1 k W m^-2.With the help of the design of the separation of the photothermal conversion layer and the evaporation layer,the high-efficiency solar photothermal conversion can be achieved under the lower light intensity.For example,under the light intensity of 0.25 k W m^-2,the photothermal conversion efficiency can reach95.83%.In addition,the simulated seawater and heavy metal wastewater can be treated by solar evaporation device.The water treated by the system could meet the relevant water standards.Industrial solid waste red mud containing various metal oxides is selected as the raw material for the preparation of photothermal conversion materials,and its composition is regulated by biomass pyrolysis reduction method.Under the heat treatment temperature of600?,the red mud containing Fe₃O₄ phase can be obtained,which can be mixed into polyvinyl alcohol?PVA?/chitosan?CS?matrix,and the red mud containing Fe₃O₄phase/PVA/CS composite freeze-drying gels can be obtained by using the freeze-drying process The results show that the composite freeze-drying gels with red mud treated at600?has the best photo thermal conversion ability when the red mud content is 20%,and its evaporation rate can reach 2.185 kg m^-2h^-1 at 1 k W m^-2.In addition,in the treatment of a variety of water,it is found that the composite freeze-drying gel has a good purification ability for multitype water.Manganese oxide/polypyrrole?PPy?composite paper electrode was prepared by coprecipitation interface-polymerization method.The paper electrode has porous structure,favourable wettability and conductivity.In 2 mol/L Na Cl aqueous solution,the highest specific capacitance is 1676.92 m F cm^-2.At the same time,compared with the blank filter paper and manganese oxide/filter paper,the composite paper electrode also has good photothermal conversion performance.Under the illumination intensity of 1k W m^-2,the evaporation rate can reach 1.355 kg m^-2 h^-1 and the photothermal conversion efficiency can reach 91.88%.Besides,when the quasi-solid state supercapacitor assembled by the manganese oxide/PPy electrode is combined with the solar photothermal interface evaporation device,the specific capacitance of this supercapacitor is about 5 times higher than supercapacitor without solar-driven water evaporation.