Preparation Of Polypyrrole-based Composites And Solar Photothermal And Electrochemical Properties

Solar-driven water evaporation technology directly converts solar energy into heat energy,heats seawater or sewage to evaporate and escape,and collects clean water after condensation.It is one of the effective methods to deal with the current shortage of water resources.The technology has been widely used in seawater desalination,sewage treatment and other water treatment fields.However,the application of solar-driven water evaporation technology combined with other fields still needs to be further explored and studied.Supercapacitors have attracted much attention characterized by high power density,high flexibility,light weight,and easy operation,but the electrochemical performance of the supercapacitor still needs to be optimized for practical applications.In views of these problems,the paper innovatively combines the solar-driven water evaporation technology and the field of electrochemical energy storage by utilizing the similar materials and structures of solar evaporators and supercapacitors,increasing the potential added value of solar evaporators and broadening the application range of solar-driven water evaporation technology.Besides,it also provides a feasible channel for improving the electrochemical performance of supercapacitors.The main research contents of the paper are as follows:The conditions of base materials,dopants,polymerization time and pyrrole amounts were optimized.The polypyrrole/filter paper with the electrochemical best performance（PPy-200）was obtained by chemical oxidative polymerization.When the polypyrrole/filter paper was used as a single electrode,a high specific capacitance of 4150 m A cm^-2 at 1 m A cm^-2had been achieved by PPy-200.Moreover,it showed a capacitance retention of 71.16%after 4000 cycles.The symmetric aqueous capacitor was composed of two PPy-200 as electrode materials and 1 M H₂SO₄ as electrolyte.The specific capacitance of the aqueous capacitor was 492.66 m F cm^-2 at 1 m A cm^-2,and the capacitance retention rate was 78.05%after 4000 cycles.At a power density of 0.35 m W cm^-2,it can deliver an energy density of33.6μWh cm^-2.The gel supercapacitor（polypyrrole/filter paper and polyvinyl alcohol/polyethylene glycol/sulfuric acid composite,PP-PPy-200）was prepared by freeze-drying,exhibiting a specific capacitance of 121.09 m F cm^-2 at 1 m A cm^-2.Utilizing the high absorbance of polypyrrole and the high wettability of filter paper,the gel supercapacitor can be used as evaporator for photothermal interface evaporation.The results showed that the evaporation rate of PP-PPy-200 can reach 1.94 kg m^-2h^-1 under one solar illumination and after 50cycles,which is better than that of PPy-200(1.54 kg m^-2h^-1).In addition,they also have good application prospects in dye removal and seawater desalination.PP-PPy-200 both have excellent electrochemical performance and solar photothermal conversion performance.Therefore,the electrochemical performance of PP-PPy-200 was improved by utilizing the dual-functional characteristics of the sample and combining solar-driven water evaporation technology with the supercapacitor.Under one solar illumination,the capacitance of PP-PPy-200 can reach 175.60 m F cm^-2 at 2 m A cm^-2,which can increase to 2.55 times than that without illumination.The solar-thermal interface evaporation technology can significantly improve the capacitance of PP-PPy-200.Its specific capacitance can reach 2.55 times than that of the original.The surface temperature of PP-PPy-200 was increased under illumination,making the water evaporation and capillary absorption synchronously.Besides,it increased the ionic migration speed and conductivity of the gel electrolyte,and thus enhancing the electrochemical performance of the supercapacitor.