Photodegradation Activity Study On Modified AgNCO Photocatalyst With Ag₂CO₃

In recent years, environmental pollution has become a worldwide problem. Industrial waste water discharged by various types of enterprises not only contains organic dyes, but also includes many heavy metal ions. However, those can’t be dealt with traditional physical method and chemical method. As a kind of green energy technology, semiconductor photocatalytic technology can remove all kinds of pollutants or kill viruses or under the irradiation of sunlight, thus has attracted more and more attention.Through different preparation methods and the synthesis strategy of adding surfactants, different morphologies of Ag₂CO₃ photocatalyst have been prepared. By ion exchange method, when Na HCO₃ as carbon source and urea as surfactant, the thin rod Ag₂CO₃ is successfully prepared through adjusting the content of urea. The relationship between its photocatalytic activity and the active crystal face is studied in detail.A novel visible light-driven AgNCO photocatalyst is prepared by a simple coprecipitation method, there seems not to be any loss of the photocatalytic activity over the Ag NCO sample after 7 cycles, which verifies that the prepared Ag NCO sample has unique photocatalytic stability under visible light. The internal resonance effect is proved to exist in Ag NCO photocatalyst through IR and XPS test results. Based on first-principles DFT, the calculation results show that the VB of Ag NCO is dominated by Ag 4d, N 2p, O 2p and the CB consists of Ag 5s and N 2s, which proves that e- and h+ can be located in Ag, N and O atoms correspondingly. From the perspective of the crystal structure, AgNCO compound is composed of zig-zag chains along the Y-axis in which the silver cation is in a two-fold coordination of（O₂C₂N₂）–Ag–（N₂C₂O₂）. The NCO^-1 acts as a bridge in contact with Ag atoms on both sides of the N, leading to a 120o of N–Ag–N formation, which acts in favor of the migration of electrons and holes. The zig-zag Ag–N–Ag chains with a bond angle of 95.847o prevent the overlap of the electron cloud of adjacent atoms of Ag–Ag to protect Ag+ from reducing.Ag₂CO₃/Ag/AgNCO Z-scheme heterojunction photocatalyst is obtained by a facile ion exchange method. Compared with Ag NCO, Ag₂CO₃, AgNCO/Ag₂CO₃ photocatalysts, Ag₂CO₃/Ag/AgNCO Z-scheme heterojunction photocatalyst shows enhanced photocatalytic activity and stability for the degradation of Rh B and reduction of heavy metal Cr⁶⁺ under visible light irradiation. SEM and TEM show that Ag nanoparticles anchor on interface between Ag NCO and Ag₂CO₃. XPS characterization proves that Ag nanoparticles exist in Ag₂CO₃/Ag/Ag NCO heterojunction photocatalyst. The fluorescence intensity of Ag₂CO₃/Ag/Ag NCO photocatalyst is the weakest in PL spectra, suggesting that Z-scheme heterojunction structure promotes the separation and transmission of the photogenerated carriers, thus enhances the photocatalytic activity. This work provides a new insight into constructing Ag-based photocatalysts and takes an important step toward the development of improving Ag-based photocatalyst activity and stability.