Interfacial Engineering of n‐p Cd ₂ In ₂ S ₅ /Co ₃ O ₄ Heterojunctions with Built‐In Electric Field: Ameliorated Charge Transfer Dynamics for Photoreforming of PET Plastic into H ₂ and Commodity Chemicals

Abstract In the quest to address the escalating plastic pollution, artificial photosynthesis offers an innovative approach to upcycling plastic waste into clean fuels and valuable chemicals. However, arduous challenges remain in the realm of photocatalysis due to the inefficient utilization of electron‐hole pairs. In this work, a n‐p heterojunction Cd ₂ In ₂ S ₅ /Co ₃ O ₄ composite with a built‐in electric field is engineered to convert an omnipresent plastic, namely polyethylene terephthalate (PET), into H ₂ (63.10 µmol h ⁻¹ ) and organic chemicals (formic acid: 8.34 µmol h ⁻¹ ; oxalic acid: 1.22 µmol h ⁻¹ ; glycolic acid: 5.22 µmol h ⁻¹ ) under the visible light irradiation. The solar‐to‐hydrogen and apparent quantum efficiency in this sacrificial‐substrate‐free system achieve a value of 0.17% and 0.48% (420 nm), respectively. The excellent performance is primarily accredited to the expanded light absorption range, enhanced specific surface area, improved carrier separation efficiency, and boosted interfacial charge transport. Advanced characterization techniques, including KPFM and EPR, uncover the intricate charge transfer dynamics of PET photoreforming, where the photogenerated holes accumulated on Co ₃ O ₄ initiate the plastic oxidation half‐reaction. Finally, the photoreforming of real‐world PET bottles demonstrates the broad universality of Cd ₂ In ₂ S ₅ /Co ₃ O ₄ hybrids. This research presents a trailblazing standpoint for the design of p‐n heterojunctions to bridge new exemplifications toward environmental sustainability.