Ag modified g-C3N4 composites with enhanced visible-light photocatalytic activity for diclofenac degradation

• Ag/g-C3N4 composite photocatalysts with different percent of Ag were prepared via a photodepostion method.
• Ag/g-C3N4 composites showed stronger light absorption and better photocatalystic activity than pure g-C3N4.
• The prepared Ag/g-C3N4 was well stable.
• The enhanced photocatalytic activity originated from the SPR of Ag and the good interface connection between Ag and g-C3N4.

Highly efficient visible-light-driven Ag/g-C3N4 heterostructured photocatalysts with different Ag amount were prepared by photodeposition under ambient condition. The composition, structure, morphology, and optical properties of the photocatalysts were characterized by X-ray powder diffraction (XRD), Fourier transform-infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), Transmission electron microscopy (TEM), UV–vis diffuse reflectance spectroscopy (DRS), and Photoluminescence Spectroscopy (PL), respectively. The results showed that photocatalytic activity of the heterostructured photocatalysts was higher than that of pure g-C3N4 through the comparison of photodegradation rates of diclofenac under visible light irradiation. When the mass ratio of Ag was 54%, the kinetic constant of diclofenac degradation over Ag/g-C3N4(54%) was 0.0429 min−1, which was almost 3.1 times higher than that of the pure g-C3N4 (k = 0.0141 min−1), showing the highest activity. Reactive species in DCF degradation were pinpointed by adding a series of scavengers into the photocatalytic reaction. Photo-generated hole was the main reactive species in diclofenac degradation. In addition, the photocatalysts showed excellent stability for the degradation of diclofenac over multiple reaction cycles. The enhanced photocatalytic activity for the photocatalyst originated from the close contact between Ag and g-C3N4, and the localized surface plasmon resonance (SPR) effect of Ag. The possible photocatalytic mechanism of the charge transfer in Ag/g-C3N4 composites was analyzed and proposed to shed into the visible light driven photocatalysis on g-C3N4 for the degradation of diclofenac.

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