Zinc phthalocyanine/polymer carbon nitride S-scheme heterojunction with internal electric field and near-infrared absorption for photocatalytic H₂O₂ production

Hydrogen peroxide (H₂O₂) serves as a critical industrial chemical and potential energy carrier. Photocatalytic synthesis presents a viable alternative to the anthraquinone process, yet existing catalyst systems exhibit restricted sunlight wavelength responses and inadequate activity. In this study, zinc phthalocyanine/polymer carbon nitride (ZnPc/PCN) S-scheme heterojunction formation extends the photocatalyst's light absorption range to the near-infrared region (400–800 nm) and generates an internal electric field at the interface, facilitating photogenerated carrier separation and transfer. ZnPc/PCN exhibits an AQY of 1.11 % for H₂O₂ production under 800 nm irradiation. The optimized ZnPc/PCN yields 1.87 mM H₂O₂, surpassing the original PCN and ZnPc by 1.36 and 93.5 times, respectively·H₂O₂ production remains above 1.5 mM (80 %) after five cycles, demonstrating ZnPc/PCN stability. Detection of intermediate ·OOH suggests H₂O₂ production via 2 e^- oxygen reduction processes. This research offers novel insights for designing near-infrared absorbing photocatalysts.