Bio-Inspired Cascade Photocatalysis on Fe Single-Atom Carbon Nitride Upcycles Plastic Wastes for Effective Acetic Acid Production

Abstract

Plastic imposes a critical threat to the environment, ecosystems, and human health because of the low utilization efficiency of plastics. Here, we demonstrate a sustainable, highly efficient cascade photocatalysis for upcycle plastics to value-added acetic acid using Fe single-atom catalysts (Fe@C3N4 SAC) at ambient conditions. Inspired by Phanerochaete chrysosporium microbial, the defective Fe@C3N4 SAC acts as a bifunctional cascade photocatalyst for both Fenton-like and CO2 reduction reactions. During the reaction, hydroxyl radicals (*OH) form and subsequently oxidize plastics into CO2 intermediates. These CO2 intermediates are then photo-reduced to CH3COOH on the same catalyst via cascade photocatalysis. The mechanism is confirmed by in situ multimodal microscopy and spectroscopies, with density functional theory calculations. A state-of-art CH3COOH yield of 63.8 mg h−1 gcat−1 from PVC, 12.7 mg h−1 gcat−1 from PE, 5.4 mg h−1 gcat−1 from PET, and 5.3 mg h−1 gcat−1 from PP are directly obtained under AM1.5G solar irradiation and further validated under real sunlight (≈0.6 sun), achieving 5.6 mg h−1 gcat−1 from PET, using low-cost Fe@C3N4 SAC in a sealed reactor by enhancing the photon transport and utilization efficiency. The techno-economic analysis shows it is promising to practically mitigate plastic based on broader social welfare assessments.