One-step preparation and photocatalytic performance of vanadium
doped TiO
2
coatings
R. Vasili
c
a, *
, S. Stojadinovi
c
a
, N. Radi
c
b
, P. Stefanov
c
, Z. Doh
cevi
c-Mitrovi
c
d
, B. Grbi
c
b
a
University of Belgrade, Faculty of Physics, Studentski trg 12-16,11000 Belgrade, Serbia
b
University of Belgrade, Institute of Chemistry, Technology and Metallurgy, Department of Catalysis and Chemical Engineering, Njego seva 12, 11000
Belgrade, Serbia
c
Institute of General and Inorganic Chemistry, Bulgarian Academy of Sciences, Acad. G. Bonchev Str., Block 11, Sofia 1113, Bulgaria
d
University of Belgrade, Institute of Physics, Pregrevica 118,11080 Belgrade, Serbia
highlights
One-step preparation of V-doped TiO
2
coatings in 10 g/L Na
3
PO
4
$12H
2
O þ 0.5 g/L NH
4
VO
3
.
Properties of obtained coatings strongly depend on microdischarge characteristics.
Band gap of V-doped TiO
2
coatings is shifted towards red side of the spectrum.
V-doped TiO
2
coatings have better photocatalytic activity than pure TiO
2
.
After 12 h of simulated sunlight irradiation, 67% of methyl orange was decomposed.
article info
Article history:
Received 2 February 2014
Received in revised form
18 September 2014
Accepted 25 November 2014
Available online 6 December 2014
Keywords:
Oxides
Coatings
Arc discharges
Atomic force microscopy (AFM)
X-ray photo-emission spectroscopy (XPS)
abstract
In this paper, we have investigated one-step preparation of vanadium doped TiO
2
coatings formed by
plasma electrolytic oxidation (PEO) of titanium in electrolyte containing 10 g/L Na
3
PO
4
$12H
2
O þ 0.5 g/L
NH
4
VO
3
. The morphology, phase structure, and elemental composition of the formed coatings were
characterized by atomic force microscopy (AFM), x-ray diffraction (XRD), and x-ray photoelectron
spectroscopy (XPS) techniques. Ultravioletevisible diffuse reflectance spectroscopy (UVeVis DRS) was
employed to evaluate the band gap energy of obtained coatings. Vanadium doped TiO
2
coatings are
partly crystallized and mainly composed of anatase phase TiO
2
, with up to about 2 wt% of vanadium
present in the surface layer of the oxide. The valence band photoelectron spectra and UVeVis DRS
showed that vanadium doped TiO
2
coatings exhibit notable red shift with respect to the pure TiO
2
coatings. The photocatalytic activity was evaluated by monitoring the degradation of methyl orange
under simulated sunlight conditions. Photocatalytic activity of vanadium doped TiO
2
coatings increases
with PEO time. Prolonged PEO times result in higher roughness of obtained coatings, thus increasing
surface area available for methyl orange degradation. Vanadium doped TiO
2
coatings obtained after 180 s
of PEO time exhibit the best photocatalytic activity and about 67% of methyl orange is degraded after 12 h
of irradiation under simulated sunlight.
© 2014 Elsevier B.V. All rights reserved.
1. Introduction
Environmental problems caused by organic pollutants from the
domestic use and industrial activity have received a great attention.
Semiconductor photocatalysis has been applied to a variety of
problems of environmental interest. Among semiconductors used
for photocatalytic degradation of environmental pollutants TiO
2
has proved itself as the unsurpassed material due to its low cost,
non-toxicity, good thermal and chemical stability, and versatile
potential applications [1e3].
Rutile and anatase are the main crystalline polymorphs of TiO
2
.
The band gap of rutile is ~3.0 eV and the band gap of anatase is
~3.2 eV. Although rutile has better irradiation response, anatase has
better photoactivity due to lower recombination rate of electron/
hole pairs [4]. However, anatase crystalline form of TiO
2
requires
* Corresponding author.
E-mail address: rastko.vasilic@ff.bg.ac.rs (R. Vasili c).
Contents lists available at ScienceDirect
Materials Chemistry and Physics
journal homepage: www.elsevier.com/locate/matchemphys
http://dx.doi.org/10.1016/j.matchemphys.2014.11.077
0254-0584/© 2014 Elsevier B.V. All rights reserved.
Materials Chemistry and Physics 151 (2015) 337e344