Construction of silver/graphitic-C3N4/bismuth tantalate Z-scheme photocatalyst with enhanced visible-light-driven performance for sulfamethoxazole degradation

Constructing Z-scheme photocatalysts is an effective way to enhance the photocatalystic performance by efficiently strengthening the charge separation. Meanwhile, the high reduction activity of conduction band electrons and oxidation activity of valence band holes are retained. In this work, we fabricated a novel ternary Ag/g-C3N4 (CN)/Bi3TaO7 (BTO) photocatalyst with remarkable visible-light response capability through the method of combining hydrothermal and photodeposition. We found that the activity of the two components Z scheme photocatalyst (CN/BTO) can be significantly improved by addition of trace amount (0.5 wt%, 1 wt%, 2 wt%) silver nanoparticles. The apparent rate constant of the optimal sample (with 1 wt% of Ag) increased by a factor of 5.6, 83.3 and 2.2 in comparison to CN, BTO and BTO/CN for sulfamethoxazole (SMZ) degradation, respectively. Based on the consequences of radicals trapping experiments and ESR, the charge transfer process were proved to be Z-scheme shift mechanism, which could hugely promote the carriers separation rate and preserve the strong redox ability. The introduced metal Ag nanoparticles have two effect on the enhanced activity: (1) served as transmission-bridges of photo-generated carriers thus boosting the separation and shift of the electron-hole pairs, (2) their SPR effect extended the range of visible light response. This work offers a good example for designing and developing extensive visible-light responsive Z-scheme photocatalysts.