Coral-like B-doped g-C3N4 with enhanced molecular dipole to boost photocatalysis-self-Fenton removal of persistent organic pollutants

Fenton process is a popular advanced oxidation process for water purification. However, it requires an external addition of H2O2, thus raising safety threats and economic costs and encountering the problems of slow cycling of Fe2+/Fe3+ and low mineralization efficiency. Herein, we developed a novel photocatalysis-self-Fenton system based on coral-like B-doped g-C3N4 (Coral-B-CN) photocatalyst for 4-chlorophenol (4-CP) removal where H2O2 can be in situ generated by photocatalysis over Coral-B-CN, the cycling of Fe2+/Fe3+ was accelerated by photoelectrons, and the photoholes promoted 4-CP mineralization. Coral-B-CN was innovatively synthesized by hydrogen bond self-assembly followed by calcination. B heteroatom doping produced enhanced molecular dipole, while the morphological engineering exposed more active sites and optimized band structure. The effective combination of the two enhances charge separation and mass transfer between the phases, resulting in efficient in-situ H2O2 production, faster Fe2+/Fe3+ valence cycling and enhanced hole oxidation. Accordingly, nearly all 4-CP can be degraded during 50 min under the combined action of more ·OH and holes with stronger oxidation capacity. The mineralization rate of this system reached 70.3%, which is 2.6 and 4.9 times higher than that of Fenton process and photocatalysis, respectively. Besides, this system maintained excellent stability and can be applied in a broad range of pHs. The study would provide important insights into developing improved Fenton process with high performance for the removal of persistent organic pollutants.