Synthesis of Visible-Light-Driven g-C3N4/PPy/Ag Ternary Photocatalyst with Improved Photocatalytic Performance

g-C3N4/PPy/Ag ternary photocatalyst was synthesized by a three-step method. Firstly, graphitic carbon nitride (g-C3N4) photocatalyst was obtained by sintering melamine at high temperature, then a series of g-C3N4/PPy composite photocatalysts were prepared by in-situ polymerization of pyrrole, and finally the g-C3N4/PPy/Ag ternary composite photocatalyst was obtained by depositing Ag on the surface of g-C3N4/PPy. The photocatalytic activities of as-prepared samples were evaluated by degradation of antibiotic tetracycline (TC) under visible light. The influence of the amounts of polypyrrole (PPy) and Ag on the photocatalytic activity of g-C3N4/PPy/Ag ternary photocatalyst was investigated. Both PPy and Ag played critical roles for the enhanced photocatalytic activity of g-C3N4/PPy/Ag. The g-C3N4/PPy/Ag composites exhibited remarkably improved photocatalytic activities for degrading TC compared with g-C3N4, g-C3N4/PPy and g-C3N4/Ag. Besides, the photocatalytic mechanism was also analyzed. The band match of PPy with g-C3N4 benefited the separation of photo-generated carriers in g-C3N4, and the deposited Ag nanoparticles played important roles as an electron mediator due to the surface plasmon resonance (SPR) effects. The present study offered new insight into the design of the economical and gently environment-friendly synthesis of highly efficient photocatalysts.