Solar Steam Generation Based On The Photothermal Effect Of Nanomaterials Absorbing Broad Spectrum:from Designs To Applications,and Beyond

Using broadband solar energy for producing clean water can potentially and effectively solve the water pollution and shortage crisis.With the rapid development of material science and nanotechnology,solar steam generation(Solar Steam Generation,SSG),based on broadspectrum absorption photothermal nanomaterials,is expanding by leaps and bounds.Under low solar power density radiation,the efficiency of SSG remains to be improved;the design of SSG system also needs to be improved;the re-application of the photothermal effect of nanomaterials is also worth exploring.This thesis summarizes the three key factors in the design of SSG systems: photothermal effect,water supply and steam escape,and thermal management;the latest research progress of various highly efficient photothermal nanomaterials,the rational design of water supply and steam escape systems,and reasonable thermal management to minimize heat loss are introduced.On this basis,the main research work carried out by the paper and the results obtained are summarized as follows:1.The solar broad-spectrum absorption copper nanoparticles are fabricated and applied to SSG.Cu nanoparticles(NPs)fabricated simply by a substitution reaction,exhibit a near-unity(97.7%)light absorption,covering a broad incident angle and wavelength range(200–1300 nm)and achieve a high photothermal conversion efficiency of 93%.By coating Cu NPs on a cellulose membrane for the first time,a SSG efficiency up to 73% can be obtained under the low power density radiation of 2 standard sun.In addition,the Cu NPs are recyclable with the high stability being resistant to heat,photoirradiation and corrosion of brine.2.The solar broad-spectrum absorption cheap carbonized kelp is prepared and applied to SSG and seawater desalination.The extremely cheap carbonized kelp with good stability,high solar absorption(93%),porous microstructure,and hydrophilic surface is found for the first time.By further improving the SSG system in Chapter 2,using polystyrene foam for thermal insulation,under a standard solar light radiation,a higher solar-to-steam conversion efficiency(84.8%)can be obtained with an evaporation rate of 1.351 kg·m-2·h-1.3.The photothermal effect of the above nanomaterials is reapplied to generate electric.An emerging solar-thermal-electric conversion system is developed based on combination of photo-thermal and thermal-electric effects.A small prototype device of 40 mm x 40 mm based on Cu NPs@Zn foil can provide an output voltage about 0.20 V under 1 standard sun.