Enhanced Charge Separation Endowed by Perylene Diimide Polymers Decorated N Vacancy on Carbon Nitride S-Scheme Heterojunction for Efficient Photocatalytic N2 Fixation.

Abstract

Designing effective photocatalyst with high charge carrier utilization for photocatalytic N₂ fixation is extremely crucial but remains a challenge. Hence, a novel p-phenylenediamine substituted perylenediimide (pPDI)/nitrogen vacancy-modified carbon nitride (NV-CN) S-scheme heterojunction photocatalyst, integrated with pPDI polymers and NV-CN, is synthesized. The introduction of bridged p-phenylenediamine units in the pPDI skeleton creates a strong built-in electric field, which can significantly enhance the separation and migration of charge. Additionally, the constructed S-scheme system greatly facilitates the interfacial photogenerated carrier separation and transfer. Meanwhile, the introduction of nitrogen vacancies into NV-CN acts as an electron trap to capture electrons, thus preventing the recombination of electron-hole pairs and significantly prolongs N₂ absorption capacity. Benefiting from these synergistic advantages, the optimized 10% pPDI/NV-CN heterojunction achieves a superior NH₃ yield of 8.83 mM g^-1 h^-1, achieving 12.26 and 13.63 times increase over CN (0.72 mM g^-1 h^-1) and PDI (0.65 mM g^-1 h^-1), respectively. This article provides an innovative perspective for the synthesis of CN-based photocatalysts for the efficient N₂ reduction through the introduction of bridging p-phenylenediamine units, nitrogen vacancy modification, and the construction of S-scheme heterojunctions.