Application Of Solar-driven Interfacial Evaporation And Photocatalytic Water Splitting Hydrogen Production In Environment And Energy

With the rapid development of economy and society,energy crisis,environmental pollution and other issues come one after another.The exploitation of clean and sustainable energy is extremely urgent.As the largest clean energy,solar energy has the characteristics of low energy density,instability and discontinuance,making it impossible for us to directly develop and use solar energy effectively on a large scale.Based on this,solar-thermal,solar-chemical and other conversion studies is rapidly setting of all over the world.Solar-driven evaporation is a direct solar-thermal energy conversion mode,its efficient conversion efficiency and the huge commercial potential behind it constantly stimulating people's nerves.At present,Solar-driven evaporation is used to drive various important industrial processes,among which the most widely used are water treatment,desalination and water purification.However,the conversion efficiency(30%-45%)of Solar-driven evaporation at low optical concentration still has much room to improve.At the same time,most of the current researches focus on desalination of seawater,relatively less on sewage treatment.Therefore,further optimization of solar-thermal conversion mechanism and more comprehensive and extensive application researches have become the top priority.Similarly,solar-chemical conversion is also considered to be one of the ways to obtain huge benefits from solar energy.Hydrogen(H2),with its clean,high combustion heat value and wide source,has touched people's hearts.Photocatalytic water splitting hydrogen production,as one of the effective methods for H2 production,has many advantages,such as no pollution,low cost,mild reaction conditions and simple operation,compared with the traditional industrial hydrogen production,mostly uneconomical,harsh reaction conditions and secondary pollution.However,efficient and stable photocatalysts and the mechanism of photocatalytic water splitting for hydrogen production still restrict the study and development of solar-hydrogen conversion.Based on the above research and development as well as the existing problems,this paper used the characteristics of solar-driven interfacial evaporation,aiming at the low solar-thermal conversion efficiency of traditional solar-driven evaporation under 1 sun irradiation,designed and constructed a Cu@CuO/CG-aero Janus membrane,which was used to improve the solar-thermal conversion efficiency,and one-step converts sewage into pure water.Then,a new idea of combining solar-driven interfacial evaporation with the photocatalytic water splitting to prepare H2 was put forward.The dual particle-size AuNPs/TiO2 photocatalyst was prepared.The synergetic effect between the two particle-size AuNPs was used to decompose water for H2 production.The specific research contents are as follows:(1)a Cu@CuO/CG-aero Janus membrane combining Cu@CuO foam made from calcined Cu foam with g-C3N4-Graphene oxide-aerogel(CG-aero)film was obtained by using a liquid nitrogen vapor freezing method.It proved that the Janus membrane is a porous structure with steam channel by analyzing its composition and microstructure.The UV-vis diffuse reflectance spectrum shows that it has excellent solar absorption.The study of thermal conductivity shows that it can concentrate the absorbed solar heat on the surface of bulk water,so as to achieve the purpose of efficient water evaporation.The results of HPLC and ICP show that the membrane material can purify dye polluted wastewater and heavy metal ion polluted wastewater,and the purified water can meet the requirements of WHO for drinking water.Similarly,the Janus membrane has a satisfactory purification effect on biological pollutants(bacteria,viruses and parasites)in water.The study of scale formation shows that the Janus membrane has good durability.(2)Dual particle-size AuNPs/TiO2 photocatalyst was synthesized by a two-step method.Triethanolamine was used as sacrificial agent to decompose water for H2 evolution.According to the statistics by using TEM,the size of large and small AuNPs are 45.0±9.8nm and 16.9±5.5 nm respectively.Photocatalytic performance tests show that the H2 escaping rate of dual particle-size AuNPs/TiO2 is 281 times than that of the pure TiO2,which is better than that of the single particle-size AuNPs/TiO2.Both optical and electrochemical properties show that the synergistic effect between large and small AuNPs in dual particle-size AuNPs/TiO2 seems to be attributed to the increase of electron-hole pairs promoted by small AuNPs and the enhancement of electron transfer caused by SPR from large AuNPs.(3)The Gold-Dicyanodiamine-directed(GDC-directed)dual particle-size AuNPs/TiO2 photocatalyst was prepared by a one-step method.In this study,the preparation method of dual particle-size AuNPs/TiO2 was improved while the synergistic effect between binary AuNPs was used.TEM results show that the sizes of large and small AuNPs are 46.3±6.1 nm and 17.3±7.5 nm respectively,which are almost the same as those of the two-step synthesis.The photocatalytic performance shows that the H2 escaping rate of GDC-directed dual particle-size AuNPs/TiO2 is higher than that of two-step synthesis.Optical properties and electrochemical tests show that the binary AuNPs in GDC-directed dual particle-size AuNPs/TiO2 play an important role in the photocatalytic process.