Combination of ultrasound-treated 2D g-C3N4 with Ag/black TiO2 nanostructure for improved photocatalysis

Herein, nanosheets of g-C3N4 (CN), prepared using a green ultrasonication process under various conditions, were combined with Ag/black TiO2 nanocomposites (AgBT) to create two-dimensional (2D) CN/Ag/black TiO2 tri-composites (CNAgBT). The thickness of the CN sheets varied with the ultrasonication conditions. The CNAgBT sample prepared using ultrasound-treated CN exhibited the highest average photocatalytic efficiencies for the degradation of two model pollutants, followed in decreasing order by AgBT, black TiO2 (BT), sheet CN, bulk CN, and TiO2. The order of pollutant degradation efficiencies by the photocatalysts was consistent with that of the charge carrier separation efficiencies. The degradation efficiency of the CNAgBT increased as the CN-to-AgBT ratio increased from 0.05 to 0.1, but decreased gradually for higher ratios between 0.15 and 0.20, indicating a lower optimal CN-to-AgBT ratio. A plausible photocatalytic degradation mechanism for the CNAgBT nanocomposites was proposed. Additionally, CNAgBT with a CN-to-AgBT ratio of 0.1 displayed a higher hydrogen generation rate with a maximum value of 21.5 mmol g−1 over 5 h than those of the AgBT and BT. Overall, the CNAgBT prepared using ultrasonication-treated CNs showed enhanced photocatalytic performance for both pollutant degradation and hydrogen generation.