Preparation And Properties Of Bismuth Sulfide Composites For Solar Steam Generation

With the rapid expansion of industry and the rapid growth of population,many countries and regions are faced with the shortage of freshwater resources.Therefore,it is urgent to develop low-consumption,clean and sustainable freshwater production technologies.Solar energy is inexhaustible,and sea water is abundant on the earth.Therefore,applying solar energy to obtaining fresh water from seawater is expected to solve the problem of fresh water shortage.The industrialized solar desalination technologies usually require photovoltaic equipment or solar collectors in the production of freshwater.The freshwater yield is quite considerable,but there are still some limitations in large-scale application.For example,the existence of fossil fuels consumption and environmental pollution or complex and precise equipment of huge desalination system make it difficult to put it into extensive application.In order to achieve high efficient freshwater production with low energy consumption and low emissions,researchers have developed a new type of solar steam generation technology.This technology utilizes photothermal effect of photothermal conversion materials to heat water,and can achieve high efficient solar steam generation and obtain freshwater without relying on any solar collectors,showing great application potential in freshwater production.However,it is still a huge challenge to explore low cost photothermal conversion materials and high efficient solar steam generation devices for large-scale application of this technology.Based on the existing researches,this thesis prepared bismuth sulfide semiconductor materials with flower-like graded structure by simple solvent thermal method.To design and prepare efficient solar steam generation devices,systematically investigated the light absorption characteristics,photothermal conversion properties and solar steam generation properties of several different bismuth sulfide composites.The main tasks are as follows:1.Investigation on the preparation and solar steam generation performance of bismuth sulfide polyvinylidene fluoride membranes(BPM):Bismuth sulfide semiconductor materials with flower-like graded structure were synthesized by solvent-thermal method,and then BPM photothermal conversion membranes were obtained by phase conversion.The BPM photothermal conversion membranes were combined with PS foam wrapped in non-woven fabric to construct solar steam generation devices.Under the illumination intensity of 1 k W m^-2,the BPM membranes achieved a water evaporation rate of 1.364 kg m^-2 h^-1,with water evaporation efficiency of 74.1%,7.5 times that of pure water.Additionally,the results of 20cycles of stability test demonstrate good water evaporation stability of this solar steam generation device,providing a new idea for the realization of high efficient solar steam generation.2.Investigation on the preparation and solar steam generation performance of bismuth sulfide/polyvinylidene fluoride composites based on polyurethane sponges(BPP):Bismuth sulfide was assembled into polyurethane sponges(PU)by phase conversion method to obtain BPP photothermal conversion sponges.This BPP evaporation sponges can achieve efficient solar steam generation without relying on the support of external insulation materials.The photothermal conversion BPP sponges can achieve 97%light absorption in the 200-2000 nm spectrum.Under the illumination intensity of 1 k W m^-2,the BPP sponges achieved a water evaporation rate of 1.66 kg m^-2 h^-1 with a water evaporation efficiency of 92.9%.Additionally,the results of 20 cycles of stability test demonstrate good water evaporation stability of this solar steam generation device.Besides,this photothermal BPP sponges exhibit excellent chemical and mechanical stability,which is expected to promote the large-scale application of solar steam generation technology in the field of freshwater production.