Construction of high-performance g-C3N4-based photo-Fenton catalysts by ferrate-induced defect engineering

Abstract

A photo-Fenton system based on the polymer semiconductor g-C₃N₄ is an important practical visible-light-driven advanced oxidation catalyst with high efficiency and low cost. However, the lack of primary photocatalytic active sites on g-C₃N₄ and the difficulty in the uniform loading of Fenton-like iron components on g-C₃N₄ decrease the performance and stability of g-C₃N₄-based photo-Fenton catalysts. Surface defect engineering, an effective strategy to enhance the photocatalytic active sites of g-C₃N₄, can improve the performances of g-C₃N₄-based photo-Fenton systems. In this work, a highly-efficient photo-Fenton catalyst with a porous structure and cyano group defects was successfully prepared by a simple one-step thermal polymerization using ferrate as a critical iron source and defect control additive. A heterogeneous photocatalysis-Fenton tetracycline degradation experiment was conducted with the addition of H₂O₂ under visible light irradiation. The as-developed CN–Fe 0.10 exhibits an 8.3 times higher removal rate than single photocatalysts, and high recycling stability. Systematic material and electrochemical characterization studies demonstrated that the ferrate-induced photo-Fenton system realized ideal coordination of the Fe–N_x coupling structure and multiple defects (intercalation defect, mesoporous defect, cyano group defect), and thus improved the separation of photogenerated charge carriers and sped up the interfacial reaction. These findings provide a new idea for smart and accurate regulation of g-C₃N₄ defects and g-C₃N₄-based complex catalysis systems using novel green reagents.