Effect of Copper-Modification of g-C 3 N 4 on the Visible-Light-Driven Photocatalytic Oxidation of Nitrophenols.

Graphitic carbon nitride (g-C 3 N 4 ) has proved to be a promising heterogeneous photocatalyst in the visible range. It can be used, among others, for the oxidative conversion of environmentally harmful nitrophenols occurring in wastewater. However, its photocatalytic activity needs to be enhanced, which can be achieved by modification with various dopants. In our work, copper-modified g-C 3 N 4 was prepared by ultrasonic impregnation of the pristine g-C 3 N 4 synthesized from thiourea. The morphology, microstructure, and optical properties of the photocatalysts were characterized by XRD, FT-IR, DRS, SEM, XPS, and TEM. DRS analysis indicated a slight change in both the CB and the VB energies of Cu/g-C 3 N 4 compared to those of g-C 3 N 4 . The efficiency of the photocatalysts prepared was tested by the degradation of nitrophenols. Copper modification caused a sevenfold increase in the rate of 4-nitrophenol degradation in the presence of H 2 O 2 at pH = 3. This dramatic enhancement can be attributed to the synergistic effect of copper and H 2 O 2 in this photocatalytic system. A minor Fenton reaction role was also detected. The reusability of the Cu/g-C 3 N 4 catalyst was demonstrated through five cycles. Copper-modified g-C 3 N 4 with H 2 O 2 proved to be applicable for efficient visible-light-driven photocatalytic oxidative degradation of nitrophenols.