Efficient Photoredox Co-Upcycling of CO2 and Plastic Waste by Band-Gap-Engineered ZnxCd1–xS Catalyst

Abstract

Solar-driven CO₂ reduction combined with plastic waste valorization presents a versatile approach to simultaneously reset misaligned hydrocarbon resources and achieve a carbon-neutral cycle. Herein, we demonstrate a co-upcycling heterogeneous photoredox catalysis for efficient CO₂ reduction to tunable syngas, integrated with polyethylene terephthalate (PET) plastic conversion for accessing acetate, over the spherical band-gap-engineered Zn_xCd_1–xS catalyst. The key to steering the syngas H₂/CO rate is to modulate the conduction band bottom potentials of the Zn_xCd_1–xS photocatalysts by altering the Zn/Cd ratio, which results in syngas H₂/CO production over a wide range. Moreover, controlled variations in the molar ratio of Zn/Cd regulate the electron–hole separation capability, thereby endowing Zn_0.8Cd_0.2S with the optimum syngas and acetate production rates. The underlying mechanistic origin of such a redox reaction involving CO₂-assisted PET plastic conversion has been systematically investigated. This win-win cooperative photoredox catalysis offers a tantalizing possibility for co-upcycling of CO₂ and PET into value-added feedstocks.