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

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.