Circumventing bottlenecks in H2O2 photosynthesis over carbon nitride with iodine redox chemistry and electric field effects

Abstract

Artificial photosynthesis using carbon nitride (g-C₃N₄) holds a great promise for sustainable and cost-effective H₂O₂ production, but the high carrier recombination rate impedes its efficiency. To tackle this challenge, we propose an innovative method involving multispecies iodine mediators (I⁻/I₃⁻) intercalation through a pre-photo-oxidation process using potassium iodide (suspected deteriorated “KI”) within the g-C₃N₄ framework. Moreover, we introduce an external electric field by incorporating cationic methyl viologen ions to establish an auxiliary electron transfer channel. Such a unique design drastically improves the separation of photo-generated carriers, achieving an impressive H₂O₂ production rate of 46.40 mmol g⁻¹ h⁻¹ under visible light irradiation, surpassing the most visible-light H₂O₂-producing systems. Combining various advanced characterization techniques elucidates the inner photocatalytic mechanism, and the application potential of this photocatalytic system is validated with various simulation scenarios. This work presents a significative strategy for preparing and applying highly efficient g-C₃N₄-based catalysts in photochemical H₂O₂ production.

H₂O₂ photosynthesis using g-C₃N₄ is considered an alternative to anthraquinone processes. Inspired by the optical instability of potassium iodide, the I⁻ /I₃⁻ internal redox mediator and external electric field are integrated into the g-C₃N₄, achieving satisfactory H₂O₂ production.