Synthesis and characterization of core-shell like Ag₂CO₃@AgBr composite photocatalyst and its high visible light photocatalytic performance

Core-shell like Ag₂CO₃@AgBr composite photocatalyst was fabricated by the successive precipitation method. The obtained AgBr, Ag₂CO₃, Ag₂CO₃@AgBr samples were well characterized by N₂ physical adsorption, powder X-ray diffraction, scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy, UV-Vis diffuse reflectance spectra, and photocurrent test. The effects of AgBr shell on the texture, light absorption, photocurrent response and photocatalytic performance for main Ag₂CO₃ photocatalyst were investigated. The results showed that Ag₂CO₃@AgBr composite displayed much stronger and broader visible light absorption than pure AgBr and Ag₂CO₃. A distinct increase in both surface area and photocurrent density for Ag₂CO₃@AgBr was observed. Under visible light (400 nm < λ < 660 nm) irradiation, the photocatalytic activity test in degradation of methyl orange (MO) dye showed that Ag₂CO₃@AgBr showed excellent photocatalytic activity and the degradation rate constant over Ag₂CO₃@AgBr (0.209 min^-1) was 14 times higher than that of Ag₂CO₃ (0.0136 min^-1), 10 times faster than that of AgBr (0.0180 min^-1). Moreover, in recycling photoactivity tests, AgBr and Ag₂CO₃ fast lost the activity, but high stabilty was obtained over Ag₂CO₃@AgBr. Between the AgBr shell and Ag₂CO₃ core, the produced intimate Ag₂CO₃/AgBr interface with matched band-gap structure largely promoted the transfer of photogenerated electrons and holes. Moreover, the AgBr shell could effectively inhibit the dissolution of Ag₂CO₃ in aqueous solution, resulting in extremely high stability.