Synthesis of three-dimensionally ordered macroporous composite Ag/Bi2O3–TiO2 by dual templates and its photocatalytic activities for degradation of organic pollutants under multiple modes

Abstract

In this study, polystyrene latex spheres and triblock copolymer surfactant EO₂₀PO₇₀EO₂₀ were used simultaneously as dual templates, with TiO₂ as a substrate to fabricate the three-dimensionally ordered macroporous (3DOM) composite Ag/Bi₂O₃–TiO₂ by a sol–gel method and post-processing calcination. The phase structure, chemical composition, morphology, and surface physicochemical properties of as-prepared samples were well characterized by X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FT-IR), Ultraviolet-visible diffuse reflectance (UV-Vis/DRS), X-ray photoelectron spectroscopy (XPS), Scanning electron microscopy (SEM), Transmission electron microscopy (TEM), and Nitrogen adsorption–desorption measurements. The investigations revealed a distinct crystalline phase structure of the composite with a uniform and ordered spherical cavity array of periodic arrangement, attributed to highly three-dimensionally ordered macroporous structure with mesoporous walls. Compared to TiO₂, the light absorption of 3DOM Ag/Bi₂O₃–TiO₂ was red-shifted, ca. 100 nm, to the visible region. The effectiveness of 3DOM Ag/Bi₂O₃–TiO₂ mediated methods for photocatalytic degradation of crystal violet by employing multi-modes such as UV, simulated solar light, and microwave-assisted irradiation was significantly enhanced compared to that of P25, Bi₂O₃, and Ag/Bi₂O₃–TiO₂. Moreover, the 3DOM Ag/Bi₂O₃–TiO₂ composite displayed excellent photocatalytic activity toward degradation of different organic pollutants using UV light irradiation. TOC analysis of the water solution phase of centrifuged samples indicated that water solution products formed and that with continued ultraviolet radiation, the intermediates eventually mineralized, volatilized, or were converted to other products. Importantly, the photocatalytic activity of 3DOM Ag/Bi₂O₃–TiO₂ was retained even after three cycles. Furthermore, based on the experimental results, the possible photocatalytic reaction mechanism of the as-prepared material was proposed.