A one-pot, solid-state route for realizing highly visible light active Na-doped gC(3)N(4) photocatalysts

The visible light photocatalytic activity of graphitic carbon nitride (gC(3)N(4)), a promising metal-free photo catalytic material, is rather low, and is not as good as expected. Herein, to realize improved photocatalytic activity, sodium-doped gC3N4 (Na-gC(3)N(4)) is prepared through a novel solid-state process based on the thermal polycondensation of urea in the presence of sodium chloride and ammonium chloride. The proposed solid-state process is simple, requires no solvent, and provides a general route for rapid and large-scale synthesis of metal doped gC(3)N(4). The Na species exist in + 1 oxidation state and bind N atoms in the nitride ring of gC3N4. The photocatalytic activity improvement of gC3N4 for the mineralization of 17 alpha-ethynylestradiol (EE2) under visible light is seen after the Na doping. The improved photocatalytic activity is due to increased absorption of light, increased separation of charge carriers, stronger oxidation ability of valance band holes, and increased specific surface area. The typical photocatalytic activity of 0.6 wt% Na-gC(3)N(4) for the EE2 mineralization with an initial EE2 concentration of 1 mg/L and a catalyst concentration of 1 g/L is 95.7% within 2 h of visible light irradiation. Under identical experimental conditions, the EE2 mineralization by pristine gC(3)N(4) is only 23.5%.