Preparation And Photothermal Conversion Performance Of Boron Nitride/Polypyrrole Composites

With the continuous development of modern processes,the energy loss is constantly intensified,at the same time,the massive use of fossil fuels leads to severe environmental damage.To achieve self-sufficiency,meet the growing global energy demand,and respond to the threat of environmental impacts and climate change caused by greenhouse gases,it is essential to make the transition to a sustainable development-based society.Developing and utilizing sustainable energy technologies to reduce the consumption of traditional energy is an urgent need.Solar energy as an environmentally friendly,renewable energy has been widely concerned.The utilization of photothermal materials is essential to improve the solar photothermal conversion efficiency.In this paper,to improve the photothermal conversion efficiency of solar energy,boron nitride with high thermal conductivity is combined with polypyrrole with high absorption performance for full spectrum to prepare a composite with high photothermal conversion ability.In this paper,sheet-and rod-shaped hexagonal boron nitride(h-BN)were used as thermal conductive materials,and ferric chloride(FeCl₃)was used as oxidant to load polypyrrole(PPy)nanoparticles on the surface of h-BN to obtain a series of h-BN/PPy composites by varying the content of pyrrole monomer.The composition components of the composites were determined by using infrared spectroscopy(FT-IR)and X-ray powder diffraction(XRD).Scanning electron microscopy(SEM)and thermogravimetric analysis(TGA)were used to explore the loading amount of polypyrrole nanoparticles on the surface of boron nitride with different morphology,and the reasons for the difference of loading amount were analyzed.The h-BN/PPy composites were dispersed in solvent(glycol-water)to fabricate into nanofluids,and the stability of the composites in solvent was investigated using UV-Vis spectroscopy.The best stable material was selected among the composites with the same morphology for the photothermal conversion experiments.The 0.05 wt%sheet-shaped composite nanofluids exhibited 36.09%higher photothermal conversion efficiency than the solvent under xenon lamp irradiation at 2 k W m^-2,and the photothermal conversion efficiency of the rod-shaped composite nanofluids is41.35%higher than that of the solvent at the same concentration.Therefore,a series of hybrid membranes containing different contents of boron nitride were obtained by physically doping the rod-shaped composites with photothermal conversion property with PVA-1799.The photothermal conversion ability of these five hybrid membranes was investigated by placing them in seawater with salt content of 3.5 wt%.The results showed that all five hybrid membranes exhibited higher evaporation rate and photothermal conversion efficiency of seawater under simulated sunlight irradiation at 1 k W m^-2.To examine the photothermal stability and salt corrosion resistance of the hybrid membranes,50 photothermal cycles were performed on the hybrid membranes with the highest photothermal conversion ability.The evaporation rate of seawater was always maintained between 1.10-1.20 kg m^-2h^-1during cycling,and the photothermal conversion efficiency only fluctuated between 76%-83%.This indicates that the hybrid membranes have high photothermal stability and salt corrosion resistance.The composites prepared in this paper as well as the hybrid membranes all exhibit good photothermal conversion ability and have some promising applications in the field of solar photothermal conversion.