PPy-coated SrTiO3-Bi composite biomass hydrogel evaporator for highly efficient seawater desalination and volatile organic compound removal

PPy/SrTiO 3 -Bi composites let biomass hydrogel evaporators combine photothermal conversion with photocatalytic degradation. • Adsorption interception coupled with photocatalytic degradation gives the evaporator excellent VOC removal efficiency. • The evaporator achieves a VOC removal efficiency of up to 99.3% under one-sun irradiation. • Under the same illumination condition, a high-water evaporation rate of 3.13 kg m −2  h −1 is also obtained. • This evaporator exhibits excellent salt resistance and water purification capabilities. Solar-driven interfacial evaporation technology has become an important approach to addressing the global water crisis due to its advantages such as being green and sustainable. However, due to the inherent volatility of volatile organic compounds (VOCs), the technology still faces severe challenges in removing VOCs from distilled water. In this paper, a biomass-based hydrogel evaporator (PSBH) integrating solar steam generation and photocatalytic degradation was constructed by immobilizing polypyrrole (PPy)-coated SrTiO 3 -Bi composites into an acrylamide (AM)/Kapok fibres composite hydrogel network via a one-pot method. This evaporator can effectively remove phenol (a typical VOC) that is volatilized along with water vapor, while achieving efficient solar-powered water evaporation. The introduction of kapok fibres endows AM hydrogels with superior structural stability and water transport efficiency, while reducing the energy required for the evaporation process, thereby enhancing the overall water transport and evaporation performance. PPy-coated SrTiO 3 -Bi composites achieve photothermal-photocatalytic synergy. The introduction of semimetal Bi nanoparticles enhances visible-light absorption and promotes spatial charge separation through its dual functional role as an electron trap and a plasmonic hot-electron donor, imparting excellent photocatalytic activity and photothermal conversion efficiency. Under 1 sun illumination, the interfacial evaporation rate can reach 3.13 kg m −2  h −1 . Meanwhile, the removal efficiency of a typical VOC (phenol) reaches 99.3%, enabling the simultaneous achievement of highly efficient seawater desalination and VOC removal. It is worth noting that the evaporation rate of this evaporator can still reach 2.22 kg m −2  h −1 in 20 wt% salt solution concentration, showing excellent environmental tolerance. This design offers a feasible strategy for multifunctional photothermal materials and a novel solution to VOCs pollution in solar interfacial evaporation. Download: Download high-res image (209KB) Download: Download full-size image