Adsorption–photocatalysis synergistic degradation of ethylene by Ag2S–TiO2–Bi2WO6 immobilized on starch/reduced graphene oxide aerogels under full-spectrum light

Abstract

To address the low quantum efficiency and poor dispersion of powdered photocatalysts in fruit and vegetable preservation, a multifunctional composite aerogel was developed by immobilizing a Z-scheme Ag₂S–TiO₂–Bi₂WO₆ heterojunction onto a three-dimensional starch/reduced graphene oxide (rGO) matrix. Ag₂S quantum dots (QDs), synthesized via γ-ray irradiation reduction, were deposited onto TiO₂–Bi₂WO₆ (TB) to construct the ternary heterojunction. The introduction of Ag₂S QDs extended light absorption into the near-infrared region and facilitated efficient charge separation via the Z-scheme pathway, significantly suppressing high-energy electron–hole recombination and enhancing quantum efficiency. Photocatalytic characterization showed that Ag₂S–TB exhibited reduced electrochemical impedance and lower photoluminescence than TiO₂, Bi₂WO₆, and TB. Under visible light, the ethylene degradation rate constant of Ag₂S–TB reached 9.54 × 10⁻⁴ min⁻¹, representing improvements of 591.30 %, 211.75 %, and 44.11 % over TiO₂, Bi₂WO₆, and TB, respectively. To further improve dispersion and gas–solid contact, Ag₂S–TB was immobilized onto a starch/rGO aerogel. The π–π interactions of rGO enhanced ethylene adsorption, while the porous starch network facilitated ethylene diffusion toward catalytic sites. At optimal loading (3.0 % internal doping, 1.5 % surface), the aerogel achieved a synergistic degradation efficiency of 33.08 % under visible light and 40.75 % under full-spectrum light. This work presents a sustainable, high-performance platform for ethylene removal via combined adsorption and photocatalysis.