Preparation of a Microspherical Silver-Reduced Graphene Oxide-Bismuth Vanadate Composite and Evaluation of Its Photocatalytic Activity

Abstract

A novel Ag-reduced graphene oxide (rGO)-bismuth vanadate (BiVO4) (AgGB) ternary composite was successfully synthesized via a one-step method. The prepared composite was characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), energy dispersive X-ray (EDX), Brunauer-Emmett-Teller (BET) surface area measurement, Raman scattering spectroscopy, and ultraviolet-visible diffuse-reflection spectroscopy (UV-vis DRS). The results showed that bulk monoclinic needle-like BiVO4 and Ag nanoparticles with a diameter of approximately 40 nm formed microspheres (diameter, 5–8 μm) with a uniform size distribution that could be loaded on rGO sheets to facilitate the transport of electrons photogenerated in BiVO4, thereby reducing the rate of recombination of photogenerated charge carriers in the coupled AgGB composite system. Ag nanoparticles were dispersed on the surface of the rGO sheets, which exhibited a localized surface plasmon resonance phenomenon and enhanced visible light absorption. The removal efficiency of rhodamine B dye by AgGB (80.2%) was much higher than that of pure BiVO4 (51.6%) and rGO-BiVO4 (58.3%) under visible light irradiation. Recycle experiments showed that the AgGB composite still presented significant photocatalytic activity after five successive cycles. Finally, we propose a possible pathway and mechanism for the photocatalytic degradation of rhodamine B dye using the composite photocatalyst under visible light irradiation.

Synthesis of Bi2S3/BiVO4 Heterojunction with a One-Step Hydrothermal Method Based on pH Control and the Evaluation of Visible-Light Photocatalytic Performance

“…The photogenerated electrons can react with dissolved oxygen molecules (O 2 ) to yield superoxide radical anions (·O 2 − ), as shown in (20), and ·O 2 − can react with H 2 O to produce ·OH (21) [55,56]. As previously mentioned, the VB of BiVO 4 can oxidize OH − to ·OH (22), and h + , ·O 2 − , and ·OH are strong oxidizing agents for the decomposition of organic dyes (23) [57]. The whole set of redox reactions can be summarized as follows: ${\mathrm{BiVO}}_4/{\mathrm{Bi}}_2{\mathrm{S}}_3+\mathrm{RhB}\to \mathrm{adsorption}$ $\mathrm{RhB}+\mathrm{normalh}\mathrm{sans-serif\nu }\to {\mathrm{RhB}}^{*}$ ${\mathrm{RhB}}^{*}+{\mathrm{BiVO}}_4/{\mathrm{Bi}}_2{\mathrm{S}}_3\to {\mathrm{BiVO}}_4/{\mathrm{Bi}}_2{\mathrm{S}}_3\left({\mathrm{e}}^{-}\right)+{\mathrm{RhB}}^{+}$ ${\mathrm{Bi}}_2{\mathrm{S}}_3+\mathrm{normalh}\mathrm{sans-serif\nu }\to {\mathrm{Bi}}_2{\mathrm{S}}_3\left({\mathrm{h}}^{+}\right)+{\mathrm{Bi}}_2{\mathrm{S}}_3\left({\mathrm{e}}^{-}\right)$ ${\mathrm{BiVO}}_4+\mathrm{normalh}\mathrm{sans-serif\nu }\to {\mathrm{BiVO}}_4\left({\mathrm{h}}^{+}\right)+{\mathrm{BiVO}}_4\left({\mathrm{e}}^{-}\right)$ ${\mathrm{Bi}}_2{\mathrm{S}}_3\left({\mathrm{e}}^{-}\right)+{\mathrm{BiVO}}_4\to {\mathrm{BiVO}}_4\left({\mathrm{e}}^{-}\right)$ ${\mathrm{BiVO}}_4$…”

Synthesis, properties and mechanism of photodegradation of core–shell structured upconversion luminescent NaYF4:Yb3+,Er3+@BiOCl

“…The photocatalytic activity of a catalyst is determined by its capacity to absorb sunlight and separate excited electron–hole pairs . Many studies have reported the basic process of this photocatalytic reaction . To prove the formation process of radicals during the photocatalytic reaction in this study, ESR analysis was employed to detect • OH and • O 2 − radicals under NIR irradiation.…”

Bismuth-Based Nanoparticles as Photocatalytic Materials

“…Nickel doped Bi 2 S 3 has also been applied in the degradation of congo red and rose bengal dyes by visible light illumination with successful results [40]. A nanocomposite consisting of BiVO 4 , Ag and reduced graphene oxide (rGO) was also synthesised and used to degrade rhodamine B dye [41]. They identified the composite to possess more photocatalytic reaction sites because of enhanced charge carriers separation ability of the BiVO 4 , electron transfer property of the silver nanoparticles and surface plasmon effect.…”