Design Of Photothermal Conversion PEDOT:PSS Hydrogel For Solar Water Purification

As a new type of water purification technology,solar-driven water purification uses sunlight as a clean and renewable energy to directly heat sewage for separation and purification,which can be used in sewage purification,seawater desalination and other fields.The construction of solar water purification interface photothermal conversion materials can effectively avoid energy loss,greatly improve the water evaporation rate,and achieve the actual demand for efficient water purification Therefore,how to construct high-efficiency has become one of the key challenges in the fields of sewage treatment and seawater desalination.The rational design of high-performance photothermal conversion materials is a key factor restricting the practical application of photothermal conversion materials.Although the past decade has witnessed rapid growth in light-to-thermal conversion materials,the corresponding limitations are still needed to solve.In contrast,poly（3,4-ethylenedioxythiophene）（PEDOT）doped with polystyrene sulfonate（PSS）exhibits excellent long-term stability and hydrophilicity,effectively ensuring that PEDOT:PSS has the excellent photothermal conversion performance and fast water transport,which makes PEDOT:PSS conjugated polymers promising for efficient and long-term stable solar water purification.Based on the above problems and materials,in this paper,poly（3,4-ethylenedioxythiophene）:polystyrene sulfonate（PEDOT:PSS）as light absorber is designed and fabricated into a series of photothermal conversion materials,such as PEDOT:PSS hydrogel with excellent light absorption ability,PEDOT:PSS-PAAm hydrogel with fast water transport ability,and long-term stable PEDOT:PSS-PVA hydrogel.We systematically study its optical properties,heat management,evaporation performance and evaporation stability and other properties,and reveal the structure-property correlation law of materials;screen out materials with excellent performance for water purification and durability tests in actual scenarios.at the same time,design and build solar water purification device for steam collection.These aim to provide theoretical guidance and technical support for research and large-scale application promotion.The specific research contents and results are as follows:1.Innovatively introduce PEDOT:PSS hydrogel into the field of solar water purification,achieving a breakthrough in the field of PEDOT conjugated polymer solar water purification.PEDOT:PSS is deposited on the surface of the wood substrate,and swelled after drying and annealing to obtain a PEDOT:PSS hydrogel photothermal conversion material with excellent light absorption ability.The surface morphology,optical properties,heat distribution,water transport performance,evaporation performance,purification capacity,and long-term stability,while exploring the structure-activity relationship between the structure and properties of materials.It is found that the PEDOT:PSS hydrogel photothermal conversion material show a strong light absorbance of 99.8%in the range of 250-2500 nm.The evaporation rate under a standard sun irradiation reaches 1.46 kg m^-2 h^-1,and its energy efficiency is as high as75.76%(better than most current photothermal conversion materials in wood systems,which the evaporation rate is<1.2 kg m^-2 h^-1.Energy efficiency<70%).By comparing the metal ions in the simulated seawater and simulated sewage before and after purification,the PEDOT:PSS hydrogel photothermal conversion material has achieved obvious purification effects,and the purified water can meet the safe drinking water standards of WHO and EPA.Meanwhile,even after 10 days of simulation testing,the energy efficiency remained stable at 70.32%.We successfully achieve the introduction of PEDOT:PSS hydrogel as a photothermal conversion material into the field of solar water purification,while achieving excellent light absorption,fast water transport,efficient water evaporation,and outstanding energy efficiency for solar water purification.2.The PEDOT:PSS-PAAm hydrogel with a double network structure is designed by chemical cross-linking,and the performance improvement of PEDOT-based conjugated polymer hydrogel photothermal conversion materials in the field of solar water purification is realized.PEDOT:PSS-PAAm hydrogels with dual network structure are obtained by chemical crosslinking with PEDOT:PSS as the photothermal network and PAAm as the water transport network.The surface morphology,optical properties,heat distribution,water transport performance,evaporation performance,purification ability and long-term stability are systematically characterized and tested,and the structure-activity relationship between the structure and properties of the materials is explored.The results show that the PEDOT:PSS-PAAm hydrogel has a high light absorption of～99.8%in a wide wavelength range of250-2500 nm,meanwhile,the water transport rate（V）of the PEDOT:PSS-PAAm hydrogel is up to～0.74 g min^-1 outperforms all previous hydrogel photothermal conversion materials(water transport rate<0.65 g min^-1).Under a standard sun irradiation it shows extraordinary energy efficiency～97.2%and high evaporation rate～2.15 kg m^-2 h^-1(better than most current photothermal conversion materials of hydrogel systems,evaporation rate<2.0 kg m^-2 h^-1,energy efficiency<90%).By comparing the salinity,metal ions,and organic pollutants in the simulated seawater and simulated sewage before and after purification,the purified water obtained by PEDOT:PSS-PAAm hydrogel photothermal conversion material can also meet the drinking water standards of WHO and EPA,as well as complete removal of organic contaminants from water.Furthermore,the PEDOT:PSS-PAAm dual network hydrogel exhibits good durability and environmental stability,achieving an excellent energy efficiency of～94.8%within 30 days.The combination of the excellent PEDOT:PSS-PAAm hydrogel photothermal conversion material and the self-developed solar steam generation equipment realizes efficient solar water purification,which lays a solid foundation for the practical application of hydrogel materials in the field of solar water purification.3.The PEDOT:PSS-PVA hydrogel with a micro-phase semi-separated structure is designed by the physical and chemical cross-linking method,and the large-scale development and practical application of PEDOT-based conjugated polymer hydrogel in the field of solar water purification are realized.The PEDOT:PSS nanofiber network is fully mixed with the PVA sol,so that the PSS microphase in the PEDOT:PSS nanofiber is partially miscible with the PVA phase,and finally a PEDOT:PSS-PVA hydrogel with a microphase semi-separated structure is formed.The surface morphology,optical properties,heat distribution,water transport properties,evaporation properties,purification capacity,long-term stability,and large-scale manufacturing and applications are systematically characterized and tested.The results show that the PEDOT:PSS-PVA hydrogel is demonstrated to exhibit a broad light absorption of～99.7%in the wavelength range of 250-2500 nm,with an unprecedented high energy efficiency of～98.0%and fast water evaporation of 2.84 kg m^-2 h^-1 under a standard sun irradiation(better than most current photothermal conversion materials of hydrogel systems,evaporation rate<2.0 kg m^-2 h^-1,energy efficiency<90%).Meanwhile,the PEDOT:PSS-PVA microphase semi-separated hydrogel still maintains a high evaporation rate of～2.71 kg m^-2 h^-1 and a stable energy efficiency of～93.3%in the 60-day practical application test.It exhibits excellent mechanical strength,long-term stability and durability（better than the long-term stability of most current photothermal conversion materials,long-term operating time<200 h,and energy efficiency<90%）.A self-contained PEDOT:PSS-PVA hydrogel photothermal conversion hydrogel material with a size of 500 mm×500 mm×5 mm is fabricated and assembled and used with a self-designed solar water purification device.We demonstrate that this device combines the material can effectively carry out seawater desalination and direct wastewater purification.To sum up,in this paper,three PEDOT:PSS conjugated polymer hydrogel photothermal conversion materials are designed,and the preparation and various kinds of hydrogel photothermal conversion materials are realized by controlling the structure.The performance test revealed the relationship between the structure and properties of the material,and provided valuable theoretical guidance for the further design of efficient photothermal conversion materials.At the same time,the large-scale fabrication of photothermal conversion materials is achieved and a variety of devices for solar water purification are designed,laying a solid foundation for the development of portable devices that are widely used in large-scale freshwater production and household or emergency needs.