Heterogeneous structure based on MXene-TiO2-Ag with biomass hydrogel for solar desalination and photocatalytic removal of VOCs

Solar interfacial evaporation technology, as an emerging sustainable water purification strategy, provides both an economical and environmentally friendly way to solve water resource problems. However, it still faces certain limitations and challenges in treating polluted wastewater containing volatile organic compounds (VOCs). In this paper, MXene-TiO 2 -Ag composites were embedded into a polyvinyl alcohol (PVA) hydrogel system using kapok fibres as biomass templates, and a bifunctional and environmentally friendly solar evaporation system (MTAH) was successfully constructed for both efficient solar freshwater production and phenol removal (typical VOC). The MTAH evaporator demonstrated excellent evaporation performance with an evaporation rate as high as 3.09 kg m −2  h −1 and a photothermal conversion efficiency as high as 93.16 % under 1 solar light intensity. The self-growth property of TiO 2 on the MXene surface endowed the evaporator with the ability of photocatalytic degradation of pollutants. In addition, the incorporation of trace Ag nanoparticles played positive roles, which not only significantly enhanced the photothermal conversion performance of MXene, but also broadened the light response range of TiO 2 and effectively suppressed the complexation of photogenerated electron-hole pairs. The MTAH evaporator shows an excellent removal rate of 91.84 % for high VOC concentrations (100 ppm phenol), effectively avoiding secondary contamination of the condensate. The finding paved the course for the sustainable and eco-friendly solution for freshwater scarcity.