oxygen-free, hot injection, and solvothermal methods, respectively (Wu et al. 2010;
Zhang et al. 2011). The photogenerated holes on the Bi 2 S 3 semiconductor have
efficient energy about 1.62 eV for oxidation of adsorbed water molecules to produce
high oxidants such as OH
• for degradation of dye contaminants (Zhang et al. 2011).
Wu et al. (2010) reported that Bi 2 S 3 nanodots and nanorods were synthesized by hot
injection method. Uniform Bi 2 S 3 nonodots show high photocatalytic degradation for
rhodamine B due to the presence of high surface area.
Bi 2 Se 3 semiconductor with the layered structure is composed from several monolayers with 0.96 nm thickness that bonded around zÀaxis with the following
configuration Se-Bi-Se-Bi-Se (Sun et al. 2012). Bi 2 Se 3 has great potential in
photoelectrochemical, optical, and thermoelectrically devices and photocatalysis
applications owing to the small band gap and high mobility of charge species (Sun
et al. 2012). Bismuth telluride (Bi 2 Te 3 ) also has very narrow band gap about 0.15 eV
with trigonal structure and high melting point. Bi 2 Te 3 applied in thermoelectric
generators and refrigeration due to the thermoelectric properties at 25
C
(Teweldebrhan et al. 2010). Big problem for Bi 2 Se 3 and Bi 2 Te 3 arrived from the
great probability of recombination rate of photogenerated electronÀhole pairs that
deprives them of the eventual photocatalytic activity.
BiOX
Bismuth oxyhalides represented by BiOX (X ¼ Cl, Br, I) can be considered as the
most famous bismuth compounds due to appropriate optical properties and high
applications in environment treatment. BiOXs have layered standings similar to
other BiÀcompounds which characterized by segments of Bi 2 O 2 interleaved by
double segments of halogens. Layered structures suggested promising large space
for polarizing orbitals and created dipoles which could led to separate charge carriers
(Lei et al. 2009).
Density functional theory calculation method simulated electrical structures of
BiÀoxyhalides (Huang and Zhu 2008). Both the valence band and conduction band
of BiOX composed of X np (n ¼ 2–5 for X ¼ F, Cl, Br, and I, respectively), O 2p,
and Bi 6p orbitals. The observed band gaps based on computations have resulted as
2.79 eV, 2.34 eV, 1.99, and 1.38 eV for BiOF, BiOCl, BiOBr, and BiOI, respectively (Zhang et al. 2008; Su et al. 2010). Results exhibited that heavy halogen has
smaller band gap. So, BiOF as photocatalyst could be excited by UV light, while
BiOI activated by visible and near-IR light. It can be stated that BiOBr and BiOCl
are repeatedly applied because of the desired amounts of band gaps. The conduction
band orbital density isosurfaces are illustrated in Fig. 10.4 for BiOX with the
involving of Bi 5d states.
BiOCl is a UV-sensitive photocatalyst with experimental band gap with range of
3.1–3.5 eV and computational calculated band gap of 2.8 eV (Zhang et al. 2006,
2016; Lei et al. 2009). Excited-BiOCl indicated eminent photocatalytic efficiency for
pollutant elimination. For instance, Zhang et al. (2006) synthesized durable BiOCl
nanoplates via simple hydrolysis method which shown high efficiency about
photodegradation of methyl orange activated by UV light. BiOCl nanosheets with
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M. Zargazi and M. Chahkandi
Zhang et al. 2011). The photogenerated holes on the Bi 2 S 3 semiconductor have
efficient energy about 1.62 eV for oxidation of adsorbed water molecules to produce
high oxidants such as OH
• for degradation of dye contaminants (Zhang et al. 2011).
Wu et al. (2010) reported that Bi 2 S 3 nanodots and nanorods were synthesized by hot
injection method. Uniform Bi 2 S 3 nonodots show high photocatalytic degradation for
rhodamine B due to the presence of high surface area.
Bi 2 Se 3 semiconductor with the layered structure is composed from several monolayers with 0.96 nm thickness that bonded around zÀaxis with the following
configuration Se-Bi-Se-Bi-Se (Sun et al. 2012). Bi 2 Se 3 has great potential in
photoelectrochemical, optical, and thermoelectrically devices and photocatalysis
applications owing to the small band gap and high mobility of charge species (Sun
et al. 2012). Bismuth telluride (Bi 2 Te 3 ) also has very narrow band gap about 0.15 eV
with trigonal structure and high melting point. Bi 2 Te 3 applied in thermoelectric
generators and refrigeration due to the thermoelectric properties at 25
C
(Teweldebrhan et al. 2010). Big problem for Bi 2 Se 3 and Bi 2 Te 3 arrived from the
great probability of recombination rate of photogenerated electronÀhole pairs that
deprives them of the eventual photocatalytic activity.
BiOX
Bismuth oxyhalides represented by BiOX (X ¼ Cl, Br, I) can be considered as the
most famous bismuth compounds due to appropriate optical properties and high
applications in environment treatment. BiOXs have layered standings similar to
other BiÀcompounds which characterized by segments of Bi 2 O 2 interleaved by
double segments of halogens. Layered structures suggested promising large space
for polarizing orbitals and created dipoles which could led to separate charge carriers
(Lei et al. 2009).
Density functional theory calculation method simulated electrical structures of
BiÀoxyhalides (Huang and Zhu 2008). Both the valence band and conduction band
of BiOX composed of X np (n ¼ 2–5 for X ¼ F, Cl, Br, and I, respectively), O 2p,
and Bi 6p orbitals. The observed band gaps based on computations have resulted as
2.79 eV, 2.34 eV, 1.99, and 1.38 eV for BiOF, BiOCl, BiOBr, and BiOI, respectively (Zhang et al. 2008; Su et al. 2010). Results exhibited that heavy halogen has
smaller band gap. So, BiOF as photocatalyst could be excited by UV light, while
BiOI activated by visible and near-IR light. It can be stated that BiOBr and BiOCl
are repeatedly applied because of the desired amounts of band gaps. The conduction
band orbital density isosurfaces are illustrated in Fig. 10.4 for BiOX with the
involving of Bi 5d states.
BiOCl is a UV-sensitive photocatalyst with experimental band gap with range of
3.1–3.5 eV and computational calculated band gap of 2.8 eV (Zhang et al. 2006,
2016; Lei et al. 2009). Excited-BiOCl indicated eminent photocatalytic efficiency for
pollutant elimination. For instance, Zhang et al. (2006) synthesized durable BiOCl
nanoplates via simple hydrolysis method which shown high efficiency about
photodegradation of methyl orange activated by UV light. BiOCl nanosheets with
326
M. Zargazi and M. Chahkandi