The preparation and characterization of TiO₂/r-GO/Ag nanocomposites and its photocatalytic activity in formaldehyde degradation

ABSTRACT

A series of TiO₂-rGO-Ag nanocomposites were prepared in this work via a facile one-pot hydrothermal method utilized for formaldehyde (HCHO) photodegradation; using TiO₂, graphene oxide(GO) as well as AgNO₃ as the raw materials, and sodium citrate as a reducing agent. Characterization by X-ray diffraction (XRD), Raman spectra, Transmission electron microscopy (TEM) and Field emission scanning electron microscopy (FESEM) demonstrated that GO and Ag⁺ were reduced during the formation of TiO₂-rGO-Ag nanocomposites. X-ray photoelectron spectroscopy(XPS), UV–vis diffuse reflectance spectroscopy (DRS), photoluminescence spectra(PL) and Photocurrent spectrum measurement were applied to quantitatively characterize the bonding between TiO₂ and rGO, the band gap energy of catalysts as well as electron–hole pairs recombination rate. The results revealed that the introduction of rGO sheets and Ag nanoparticles reduced the band gap energy of catalysts; it also suppressed the recombination of electron–hole pairs. However, C–O–Ti bond, which played a key role in photocatalysis, was reduced to some extent by the existence of Ag. Photodegradation results showed that, when the Ag loading was 9 mol% of TiO₂, the reaction rate constant of formaldehyde (HCHO) removal improved distinctly, by about 22.3 times that of TiO₂. The radical scavenger tests and electron paramagnetic resonance(EPR) analysis revealed that superoxide radical (·O₂⁻), hole (h⁺), and hydroxylradical (·OH) were reactive species of formaldehyde photodegradation.

GRAPHICAL ABSTRACT

KEYWORDS:

• TiO₂
• reduced graphene oxide(rGO)
• Ag
• formaldehyde photodegradation
• C–O–Ti bonding

Disclosure statement

The authors declare no potential conflict of interest.