One-pot synthesis of Ag-modified LaMnO3–graphene hybrid photocatalysts and application in the photocatalytic discoloration of an azo-dye

Abstract

Ag-modified LaMnO₃–graphene nanocomposites were successfully synthesized by the sol–gel technique. The nanocomposites were characterized by X-ray diffraction, field-emission scanning electron microscopy with energy dispersive spectrometer, transmission electron microscopy, X-ray photoelectron spectroscopy, Brunauer–Emmett–Teller surface area analysis and photoluminescence analysis. High-efficiency degradation of Direct Green BE under UV-vis light was achieved for Ag/LaMnO₃–graphene as photocatalyst. The enhancement of UV-vis photocatalytic activity can be attributed to the high separation efficiency of photoinduced electron–hole pairs resulting from the excellent conductivity of Ag in composites and the formation of multistage drill way, which can promote the adsorption of organic dyes and improve the transfer efficiency of the photocatalytic process. The photocatalytic mechanism was studied by adding hydroxyl radical (˙OH), superoxide radical (˙O²⁻), and active hole (h⁺) scavengers. The results confirmed that h⁺ generated in Ag/LaMnO₃–graphene played a key role in photocatalysis, with the assistance of ˙OH. By contrast, ˙O²⁻ had the least influence on the process.