Dipole field and locally polarized electric field in asymmetric crystalline carbon nitride for high-efficiency artificial photosynthesis of hydrogen peroxide

Abstract

Artificial photosynthesis of hydrogen peroxide (H₂O₂) represents a safe, environmentally friendly, and energy-efficient route, but the unestablished charge transfer channels and high surface inertness restrict the overall photocatalytic efficiency. Herein, a highly asymmetric crystalline carbon nitride (MTCN) is developed by synchronous introduction of polar triazole moiety and cyanide group for efficient H₂O₂ photosynthesis. The construction of intramolecular donor-acceptor structure with remarkable discrete electron distribution, results in synergistic dipole moment augment from 1.5 for symmetric CN to 10.2 for MTCN, achieving efficient directional electron migration to cyanide group occupied tri-s-triazine rings. In-situ irradiation X-ray photoelectron spectroscopy, density functional theory simulations and in situ diffuse reflectance infrared spectroscopy proves that the cyano groups act as reactive sites for O₂ reduction, and the as-induced locally polarization can cooperate with dipole field to facilitate the highly-selective two-step single-electron O₂ reduction process. Thus, MTCN achieves a H₂O₂ evolution rate enhancement of over two orders of magnitude, and accumulates a recording H₂O₂ yield of 70 mmol g⁻¹ under visible light within 8 h, which can be directly applied to the seconds-level decomposition of Rhodamine B. It also holds a sustainable H₂O₂ generation capability at an ultra-high initial H₂O₂ concentration of 12.5 mM. The findings present an innovative approach to design efficient and sustainable photosynthesis catalysts via molecular tailoring and polarization field modulation.