Copper atom-doped g-C3N4 nanocomposites for enhanced photocatalytic degradation of tetracycline

Inorganic photocatalysts with excellent photocatalytic reactivity have significant potential for wastewater treatment. In this study, using sodium copper chlorophyllin (SCC) as a copper source, Cu atoms were incorporated into the center cavities of g-C3N4 nanosheets by hydrothermal-calcination combined processes. Cu atoms doping led to a narrower optic band gap and the dramatic improvement in photocurrent response as well as corresponding declines in the intensity of electrochemical impedance spectroscopy (EIS) and photoluminescence (PL) spectra. Consequently, the photocatalytic property the Cu/g-C3N4 was enhanced dramatically as evidenced by a 53.4% increase in the photocatalytic degradation rate of tetracycline. Superoxide ions and hydroxyl radicals were found to be the main reactive oxygen species (ROS) causing the degradation. The increased photocatalytic capability of Cu/g-C3N4 might be attributed to the increased chance of intersystem crossing in photosensitizing process of Cu/g-C3N4 as well as the lowered adsorption energy required for the adsorption of O2 to the catalyst. Minor decline in the photocatalytic efficiency of Cu/g-C3N4 was observed while the crystal structure of the Cu/g-C3N4 remained stable after three cycles of tetracycline degradation. These results indicated the good stability of Cu/g-C3N4 and the possibility of recycling the catalyst during the photocatalytic applications.