Two-Dimensional, Hierarchical Ag-Doped TiO2 Nanocatalysts

Effect of the Metal Oxidation State on the Photocatalytic Properties

Siti Khatijah Md Saad, Ali Umar Akrajas, Marjoni Imamora Ali Umar, Masahiko Tomitori, Mohd Yusri Abd Rahman, Muhamad Mat Salleh, Munetaka Oyama

Research output: Contribution to journalArticle

9 Citations (Scopus)

Abstract

This paper reports the synthesis of two-dimensional, hierarchical, porous, and (001)-faceted metal (Ag, Zn, and Al)-doped TiO2 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.

Original languageEnglish
Pages (from-to)2579-2587
Number of pages9
JournalACS Omega
Volume3
Issue number3
DOIs
Publication statusPublished - 1 Jan 2018

Fingerprint

Nanostructures
Metals
Oxidation
rhodamine B
Doping (additives)
Methenamine
Degradation
Electrons
Photocatalysis
Nanosheets
Defect density
Surface reactions
Oxygen vacancies
Binding energy
Ammonium Compounds
Light sources
Hydrolysis
Rate constants
X ray photoelectron spectroscopy

ASJC Scopus subject areas

  • Chemical Engineering(all)
  • Chemistry(all)

Cite this

Two-Dimensional, Hierarchical Ag-Doped TiO2 Nanocatalysts : Effect of the Metal Oxidation State on the Photocatalytic Properties. / Md Saad, Siti Khatijah; Akrajas, Ali Umar; Ali Umar, Marjoni Imamora; Tomitori, Masahiko; Abd Rahman, Mohd Yusri; Mat Salleh, Muhamad; Oyama, Munetaka.

In: ACS Omega, Vol. 3, No. 3, 01.01.2018, p. 2579-2587.

Research output: Contribution to journalArticle

Md Saad, Siti Khatijah ; Akrajas, Ali Umar ; Ali Umar, Marjoni Imamora ; Tomitori, Masahiko ; Abd Rahman, Mohd Yusri ; Mat Salleh, Muhamad ; Oyama, Munetaka. / Two-Dimensional, Hierarchical Ag-Doped TiO2 Nanocatalysts : Effect of the Metal Oxidation State on the Photocatalytic Properties. In: ACS Omega. 2018 ; Vol. 3, No. 3. pp. 2579-2587.
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