CdS quantum dots with sulfur defects for photoreforming plastics into valuable chemicals coupled with hydrogen production

Abstract

Photocatalytic reforming of plastics, involving converting plastics into valuable chemicals while producing hydrogen from water, is a promising green technology with sustainability potential. However, designing catalysts with optimized structures to further enhance efficiency remained a major challenge. In this study, a series of CdS Quantum dots (QDs) with different sulfur defect concentrations were synthesized by a one-step solvothermal method by adjusting the type of sulfur precursors. In the absence of co-catalysts, the optimal CdS-NS photocatalyst achieved reforming of polyethylene terephthalate (PET) into formate with 870 μmol g⁻¹ h⁻¹ and acetate esters with 90 μmol g⁻¹ h⁻¹, while the hydrogen production rate reached 1771 μmol g⁻¹ h⁻¹. EPR spectra and other analyses confirmed the presence of abundant sulfur defects in the prepared CdS QDs and further demonstrated that the concentration of sulfur defects was closely related to photocatalytic performance. Suitable sulfur defects effectively modulated the electronic and band structure of CdS QDs, enhanced the oxidation capacity of photogenerated holes, reduced the recombination rate of charge carriers, and ultimately improved photocatalytic activity. This work provided an effective approach for designing efficient photocatalysts for the high-value recycling of plastic waste to achieve carbon neutrality.