Upcycled PET-Derived Carbon Foam Functionalized with Cu3SbS4-Sb2S3 Heterostructures for Efficient Interfacial Solar Desalination.

Solar desalination is an emerging technique to produce fresh water utilizing renewable solar energy. However, the engineering of efficient photothermal material is a significant obstacle. In the present study, a carbon foam is synthesized from the upcycling of waste PET and hydrothermally functionalized with a heterostructure composed of Cu₃SbS₄ and Sb₂S₃. Material characterizations demonstrated the successful decoration of nanochannels on graphitic carbon foam (CF). The analysis of the optical properties in the UV/Vis-NIR spectral range demonstrated excellent absorption properties of 96% for Cu₃SbS₄-Sb₂S₃/CF compared to Sb₂S₃/CF (48%) and CF (68%) in near-IR. Photothermal desalination results reveal the evaporation rate of 2.82 kg m^-2 h^-1 for Cu₃SbS₄-Sb₂S₃/CF compared to  1.4 kg m^-2 h^-1 for Sb₂S₃/CF and  1.58 kg m^-2 h^-1  for CF, with 99% salt removal in condensed water. The formation of the composite leads to a high surface temperature and enhanced evaporation rate. The contact angle analysis confirmed the hydrophilic nature of the material that plays a crucial role in the solar desalination process. These findings elucidate the effective photothermal performance achieved through chalcogenide heterostructure engineering supported on upcycled carbon foam derived from waste PET, demonstrating a practical application aligned with circular economy principles in solar desalination.