Cobalt modified mesoporous graphitic carbon nitride with enhanced visible-light photocatalytic activity

Mesoporous graphitic carbon nitride (mpg-C3N4) was synthesized using silica nanoparticles as the hard template, and cobalt modified mpg-C3N4 (Co3O4/mpg-C3N4) was prepared via a facile impregnation method. UV-vis spectra showed that the mpg-C3N4 exhibited obvious absorption in the visible light range. The XPS results proved that the cobalt species deposited on mpg-C3N4 samples was Co3O4. The photocatalytic activity of Co3O4/mpg-C3N4 was evaluated in the photocatalytic degradation of bisphenol A (BPA) in aqueous solutions under visible light irradiation (lambda > 420 nm). The photocatalytic degradation efficiency of BPA by Co3O4/mpg-C3N4 was significantly higher than that of mpg-C3N4 and the optimum content of Co3O4 loaded in the mpg-C3N4 was 1.5 wt%. Radical-trapping experiments certified that both hydroxyl radicals and superoxide radicals were the active species for the photocatalytic degradation of BPA. The total organic carbon (TOC) removal showed that BPA was mineralized by 1.5% Co3O4/mpg-C3N4 under visible light irradiation. The recycling tests indicated that 1.5% Co3O4/mpg-C3N4 was quite stable and there was no obvious decrease in photocatalytic activity after 5 cycles.