Two-Dimensional, Hierarchical Ag-Doped TiO₂ Nanocatalysts: Effect of the Metal Oxidation State on the Photocatalytic Properties

Abstract

This paper reports the synthesis of two-dimensional, hierarchical, porous, and (001)-faceted metal (Ag, Zn, and Al)-doped TiO 2 nanostructures (TNSs) and the study of their photocatalytic activity. Two-dimensional metal-doped TNSs were synthesized using the hydrolysis of ammonium hexafluorotitanate in the presence of hexamethylenetetramine and metal precursors. Typical morphology of metal-doped TNSs is a hierarchical nanosheet that is composed of randomly stacked nanocubes (dimensions of up to 5 μm and 200 nm in edge length and thickness, respectively) and has dominant (001) facets exposed. Raman analysis and X-ray photoelectron spectroscopy results indicated that the Ag doping, compared to Zn and Al, much improves the crystallinity degree and at the same time dramatically lowers the valence state binding energy of the TNS and provides an additional dopant oxidation state into the system for an enhanced electron-transfer process and surface reaction. These are assumed to enhance the photocatalytic of the TNS. In a model of photocatalytic reaction, that is, rhodamine B degradation, the AgTNS demonstrates a high photocatalytic activity by converting approximately 91% of rhodamine B within only 120 min, equivalent to a rate constant of 0.018 m –1 and ToN and ToF of 94 and 1.57 min –1 , respectively, or 91.1 mmol mg –1 W –1 degradation when normalized to used light source intensity, which is approximately 2 times higher than the pristine TNS and several order higher when compared to Zn- and Al-doped TNSs. Improvement of the crystallinity degree, decrease in the defect density and the photogenerated electron and hole recombination, and increase of the oxygen vacancy in the AgTNS are found to be the key factors for the enhancement of the photocatalytic properties. This work provides a straightforward strategy for the preparation of high-energy (001) faceted, two-dimensional, hierarchical, and porous Ag-doped TNSs for potential use in photocatalysis and photoelectrochemical application.

Correction: Photocatalytic antibacterial performance of TiO2 and Ag-doped TiO2 against S. aureus. P. aeruginosa and E. coli

“…As expected from previous works on similar Ag-doped TiO 2 nanoparticles [1][2][3][4][5], the diffraction peaks associated with Ag were not easily observed. Similar to these prior works, the pres- ence of Ag did not cause changes in the TiO 2 anatase crystalline structure and no significant high intensity peaks related to fcc Ag were observed.…”

Sb-Doped Titanium Oxide: A Rationale for Its Photocatalytic Activity for Environmental Remediation

“…Recent studies have shown that the improvement of the photocatalytic properties of the TiO 2 doped with transition metals can also be seen in terms of modification of density of state of the VB that includes the change in the d-orbital shape and broadening. 65…”

2D Titanium/Niobium Metal Oxide‐Based Materials for Photocatalytic Application

“…By comparison, the photocatalytic activity of the Ag + ‐doped sample was higher than that of Cu 2+ one. Furthermore, Ag atoms were also doped into other 2D TNMOs to improve the photocatalytic activity, such as 2D TiO 2 nanocatalyst, K 4 Nb 6 O 17 , RbLaNb 2 O 7 , and RbA 2 Nb 3 O 10 (A = Ca and Sr) …”