Abstract:

Graphitic carbon nitride supported nano-Ag（Ag/g-C₃N₄） composites were prepared by photoreduction method using AgNO₃ and g-C₃N₄ as precursors and polyvinylpyrrolidone as inhibitor.The Ag/g-C₃N₄ composites were characterized by X-ray diffraction（XRD），Fourier transform infrared spectroscopy（FT-IR），photoluminescence spectroscopy（PL），ultraviolet-visible diffuse reflectance spectroscopy（UV-vis DRS），transient photocurrent spectroscopy（TPC） and electrochemical impedance spectroscopy（EIS）.The crystal phase，functional groups，spectral absorption range，photoelectron-hole recombination and charge transfer resistance of Ag/g-C₃N₄ composites were systematically characterized and analyzed.The photocatalytic activity and stability of Ag/g-C₃N₄ composites under visible light were investigated by using methylene blue（MB） dye solution as the target substrate.The results showed that the construction of Schottky heterojunction between nano-Ag and g-C₃N₄ and the plasma resonance effect effectively promoted the separation of photoelectron-holes and broadened the spectral absorption range.The low charge mass transfer resistance promoted the charge transfer and effectively improved the photocatalytic activity.The degradation rate of MB dye solution by Ag/g-C₃N₄ composite reached 98.9% within 60 min of visible light irradiation，and the degradation rate of MB dye solution still reached 98.3% after 5 cycles，showing good stability.The coexistence of inorganic salt ions such as HCO₃^-，CO₃^2- and NO₃^- would affect the photocatalytic reaction.Highly active photoelectrons reduced O₂ to superoxide radicals，and the generated superoxide radicals were involved in the photocatalytic degradation of MB dye solution.

Key words: Ag/g-C₃N₄, photocatalysis, methylene blue, light reduction method, schottky, plasma resonance effect