Built-in electric field accelerates photogenerated carrier separation in vanadium-oxygen doped C3N4 for flash degradation of methylene blue: Experimental and molecular simulations

Flash photodegradation of organic pollutants at high concentrations is an urgent need for industrial organic wastewater treatment. Situ high-energy wet ball milling is adopted to fabricate the vanadium-oxygen doped carbon nitride catalysts to implement the flash degradation of methylene blue (MB). The experimental results indicated that the photocatalyst degradation ratio of MB was higher than 90% in 3 min under visible-light irradiation 300 W, catalyst dosage 0.2 g/L and MB concentration of 100 mg/L. MB removal rate was nearly 20 times higher than that of primitive carbon nitride. Vanadium-oxygen doping was beneficial to the reduction of band gap less than 2.0 eV and the formation of built-in electric field. It is notable notice that both valence band and conduction band of catalyst were tuned to be in positive potential region, benefiting for holes (h + ) formation to boost the flash degradation of contaminants. Strong electrophilic attack of h + caused the bonds of C-S + =C and C N-C broken, triggering the aromatic ring opened to decompose into smaller molecules.