The influence of synthesis conditions on the visible-light triggered photocatalytic activity of g-C3N4/TiO2 composites used in AOPs

Different synthesis temperatures (450–550 °C) were applied to synthesize g-C 3 N 4 with the highest visible-light triggered photocatalytic activity. The best performing g-C 3 N 4 photocatalyst was synthesized at 550 °C due to the created favourable structure that expressed the lowest band gap and charge carrier recombination rate. To further improve the photocatalytic activity of g-C 3 N 4 , different g-C 3 N 4 /TiO 2 (gCN/TNP) composites with varying weight concentrations of g-C 3 N 4 and TiO 2 were prepared. Charge carrier separation was enabled due to the injection of photogenerated electrons from the g-C 3 N 4 conduction band (CB) to the TiO 2 CB, where they reacted with water-dissolved oxygen to form reactive oxygen species. The best performing composite was 0.50gCN/TNP 2 h with 50 wt% of g-C 3 N 4 and 2 h calcination at 350 °C. The improved photocatalytic activity is due to an appropriate ratio between the shielding effect of TiO 2 , higher contact area and the consecutive improvement of the charge carrier separation, which is the key determining factor.