“…In addition, a p-n junction is formed between p-type BiOI and n-type TiO 2 when Fermi levels reached equilibrium, which facilitate photo-induced electrons to migrate from CB of BiOI to that of TiO 2 [17, 34]. Similarly, a type II heterojunction is formed between p-type CdTe [18] and TiO 2 microspheres; thus, electrons in the CB of CdTe QDs can transfer to TiO 2 [35]. Therefore, the lifetime of the photogenerated electron and hole is prolonged, which is beneficial for the degradation towards MO.Scheme 2Illustration of photo-induced charge transfer in ternary TiO 2 /CdTe/BiOI photocatalytic system…”
Section: Resultsmentioning
confidence: 99%
“…To solve the issues mentioned above, multi-component heterojunction systems have been developed. Cadmium telluride (CdTe), as an important p-type II−VI compound semiconductor, has received much attention because of its direct bandgap of 1.44 eV [18] and a large optical absorption coefficient in the solar spectrum [19]. CdTe quantum dots (CdTe QDs) have been widely used to modify various semiconductors: Feng et al [20] synthesized the CdTe-decorated TiO 2 nanotube arrays via a pulse electrodeposition method, and the results indicated CdTe/TiO 2 nanotube arrays (CdTe/TiO 2 NTAs) exhibited outstanding photocatalytic property than the bare TiO 2 NTAs; Liu et al [21] reported the synthesis of CdTe/ZnO nanocomposites by a hot bath method, and the results showed that CdTe/ZnO owed a better photocatalytic activity for Rhodamine B than bare ZnO.…”
Hollow and heterostructured architectures are recognized as an effective approach to improve photocatalytic performance. In this work, ternary TiO
2
/CdTe/BiOI with hollow structure was constructed via a step-by-step method. In addition, the effect of TiO
2
structural regulation and the energy band alignment of BiOI and CdTe quantum dots (CdTe QDs) with TiO
2
in TiO
2
/CdTe/BiOI on photocatalytic dye removal were also studied. The results reveal that the TiO
2
/CdTe/BiOI heterostructures with hollow substrates exhibit much higher photocatalytic activities than pure TiO
2
, P25, TiO
2
/CdTe, and TiO
2
/BiOI and ternary TiO
2
/CdTe/BiOI with solid substrates. For TiO
2
(H)/CdTe/BiOI, several synergistic factors may be responsible for the remarkable visible-light photodegradation performance, such as strong visible-light absorption by BiOI and larger specific surface area.
“…In addition, a p-n junction is formed between p-type BiOI and n-type TiO 2 when Fermi levels reached equilibrium, which facilitate photo-induced electrons to migrate from CB of BiOI to that of TiO 2 [17, 34]. Similarly, a type II heterojunction is formed between p-type CdTe [18] and TiO 2 microspheres; thus, electrons in the CB of CdTe QDs can transfer to TiO 2 [35]. Therefore, the lifetime of the photogenerated electron and hole is prolonged, which is beneficial for the degradation towards MO.Scheme 2Illustration of photo-induced charge transfer in ternary TiO 2 /CdTe/BiOI photocatalytic system…”
Section: Resultsmentioning
confidence: 99%
“…To solve the issues mentioned above, multi-component heterojunction systems have been developed. Cadmium telluride (CdTe), as an important p-type II−VI compound semiconductor, has received much attention because of its direct bandgap of 1.44 eV [18] and a large optical absorption coefficient in the solar spectrum [19]. CdTe quantum dots (CdTe QDs) have been widely used to modify various semiconductors: Feng et al [20] synthesized the CdTe-decorated TiO 2 nanotube arrays via a pulse electrodeposition method, and the results indicated CdTe/TiO 2 nanotube arrays (CdTe/TiO 2 NTAs) exhibited outstanding photocatalytic property than the bare TiO 2 NTAs; Liu et al [21] reported the synthesis of CdTe/ZnO nanocomposites by a hot bath method, and the results showed that CdTe/ZnO owed a better photocatalytic activity for Rhodamine B than bare ZnO.…”
Hollow and heterostructured architectures are recognized as an effective approach to improve photocatalytic performance. In this work, ternary TiO
2
/CdTe/BiOI with hollow structure was constructed via a step-by-step method. In addition, the effect of TiO
2
structural regulation and the energy band alignment of BiOI and CdTe quantum dots (CdTe QDs) with TiO
2
in TiO
2
/CdTe/BiOI on photocatalytic dye removal were also studied. The results reveal that the TiO
2
/CdTe/BiOI heterostructures with hollow substrates exhibit much higher photocatalytic activities than pure TiO
2
, P25, TiO
2
/CdTe, and TiO
2
/BiOI and ternary TiO
2
/CdTe/BiOI with solid substrates. For TiO
2
(H)/CdTe/BiOI, several synergistic factors may be responsible for the remarkable visible-light photodegradation performance, such as strong visible-light absorption by BiOI and larger specific surface area.
“…[ 15 ] . Recently, the ZnO {001} polar planes have been found to have enhanced photocatalytic CO 2 reduction activity, [ 22 ] In addition to ZnO{001}, hexagonal phase CdS{001}, [ 23–26 ] CdSe{001} [ 27 ] and Cu‐Zn‐In‐S{001}, [ 28 ] cubic phase CoO{111}, [ 29 ] CdTe{111}, [ 30 ] NiO{111}, [ 31 ] Cu 2 O{111}, [ 32,33 ] Cu 2 Se{111}, [ 34 ] Cu 2 O/Cu 2 Se{111}, [ 35 ] and Zn 0.67 Cd 0.33 S{111} [ 36 ] as well as tetragonal phase anatase TiO 2 {111} [ 37,38 ] crystal facets have been reported to be the reactive surfaces for photocatalytic decomposition of organic dyes, [ 23,24,27,29–33 ] photocatalytic H 2 generation [ 25,26,28,35–37 ] and CO 2 reduction. [ 38 ]…”
Section: Polar Crystal Facets and Their Photochemical Reactionsmentioning
confidence: 99%
“…Reproduced with permission. [ 30 ] Copyright 2017, Elsevier. j,k) NiO{111}.…”
Section: Polar Crystal Facets and Their Photochemical Reactionsmentioning
As we know, photocatalytic reactions occur at the surfaces of catalysts, thus the photocatalytic performance of a catalyst is strongly related to its exposed crystal faces, which determines the surface structure at the atomic scale. [11,12] Recently, the separation of photoinduced charges on the exposed faces of semiconductor nanocrystals has been studied using surface photovoltage techniques [13] and synchronous illumination X-ray photoelectron spectroscopy. [14] However, these studies only focus on one crystal facet, and the structures at atomic scale of the reactive facets of the semiconductor photocatalysts have never been taken into consideration. Based on the atomic arrangement of ZnO photocatalytic reactive polar {001} planes, we present a model of photo-produced charge separation promoted by an interior electric field between Zn-ZnO (001) and O-ZnO (001) crystal planes for the first time. [15] Here, we provide evidence that the charge separation between polar facets is a general photocatalytic reaction mechanism by demonstrating the polar structures of facets with photocatalytic activity, photo-induced selective redox reactions on polar planes, and photovoltaic and rectification effects in polar-direction-orientated semiconductor thin film.
Polar Crystal Facets and Their Photochemical Reactions
Polar Crystal Facets with Enhanced Photocatalytic ActivityChoy et al. [16] have first observed that ZnO nanoplates with exposed {001} crystallographic planes exhibit higher photocatalytic activity for H 2 O 2 generation compared with ZnO microrods and dumbbell-shaped microrods. Subsequently, hexagonal ZnO quantum dots [17] and nanodisks [18] and porous nanodisks [19] with dominant {001} crystal faces were found to display enhanced photocatalytic activity in the decomposition of rhodamine B [17,18] and methyl orange. [15,19] Thus, the exposed ZnO {001} crystal planes are regarded as the active surfaces for photocatalytic decomposition of organic dyes. According to the literature, [15,20] the exposed {001} surfaces of wurtzite ZnO are polar, which are comprised of a positive Zn-ZnO(001) and a negative O-ZnO (001) surface. The [001] of ZnO is a polar direction. In the [001] direction, Zn and O are not located at the same atomic layer. The Zn and O atoms are positively and negatively charged, respectively. The positive Zn-and negative O-atomic layers stack alternately along the [001] direction (Figure 1a,b).Until now, the photogenerated charge separation mechanism is not clear in photocatalysis. Based on the structures at the atomic scale of the polar crystal facets with photocatalytic activities, a general separation model of photogenerated charge between polar facets under a spontaneous electric field is presented. This charge separation model is proven by photo-induced selective redox reactions on polar planes, photovoltaic and rectification effects in the polar direction orientated thin films, and electric field assisted assembly and alignment of semiconductor nanowires grown along the polar direction. This polar s...
“…An intensively investigated method for water treatment is photocatalysis, which has been recognized as a convenient, green and inexpensive technology for the complete decomposition of organic pollutants into H 2 O and CO 2 [2][3][4]. Up to now, numerous semiconductors (TiO 2 , ZnO, CdS, ZnS, CdTe, α-Fe 2 O 3 , BiOI or SrTiO 3 ) were applied as photocatalysts [5][6][7][8][9][10]. Among them, ZnO has become known as an efficient and promising candidate in pollutants removal due to its unique characteristics, such as direct and wide band gap (3.37 eV), good photocatalytic property, large area-to-volume ratio, environmentally friendly nature and low cost [11].…”
Hybrid polymeric materials, due to the unique combination of properties that can be obtained by the convenient variation of organic and inorganic components, represent an attractive alternative for many applications, especially photocatalysis. Herein, we report the preparation of nanocomposite films containing functionalized ZnO nanoparticles, as well as in situ photogenerated noble metal nanoparticles (Ag, Au, Pd), for the achieving of materials with enhanced photocatalytic activity under visible light. The flexible free-standing nanocomposite films were synthesized by photopolymerization of a monomer mixture (silane castor oil urethane dimethacrylate and polypropylene oxide urethane dimethacrylate) in the presence of a Irgacure 819 photoinitiator. The efficiency of ZnO NPs functionalization was established by Fourier transform infrared spectroscopy (FTIR) and thermogravimetric analysis, while the polymer composites were characterized by UV-Vis spectroscopy, X-ray diffraction, transmission electron microscopy and scanning electron microscopy to evidence the formation, size and distribution of the nanoparticles inside the photocrosslinked matrix. To establish the photocatalytic capacity of nanocomposite films, the decomposition of various pollutants (methyl orange, phenol, metronidazole) was monitored under visible light irradiation, the best results being obtained for Au/ZnO film. Also, the advantage of immobilizing the catalysts in a polymeric support and its recycling ability without a significant decrease in photocatalytic efficiency was analysed.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
