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Inducing amorphous components into Al2O3 leads to elongation of the Al–O bond and the formation of oxygen vacancies, which makes Al2O3 an independent photocatalyst for CO2 adsorption and reduction.

In this paper, it is found that the preferential growth of secondary {117} facets of Bi24O31Br10 into dominant facets would lead to higher photocatalytic activity, although the original main {213} facet has a stronger molecular oxygen adsorption ability, which illustrates that the charge separation efficiency induced by dominant/secondary facet control plays a more important role than that of O2 adsorptive performance in improving activity.

Hierarchical porous CoFe-LDHs composed of ultrathin nanosheets were successfully prepared by a simple one-step precipitation process of Co2+ and Fe3+ ions, avoiding multiple tedious steps. The optimized composition and the hierarchical porous structure design of the CoFe-LDHs endow them with high activity for OER in alkaline media (1 M KOH). Benefiting from the synergistic catalytic effects of the controllable composition and the structural features of CoFe-LDHs, the superior OER performance of hierarchical porous Co8Fe1-LDH nanosheets with optimal composition is achieved with the smallest overpotential (262 mV at 10 mA cm−2), lowest Tafel slope (42 mV per decade), and excellent long-term stability, which is superior to previously reported LDH-derived and commercial iridium dioxide (IrO2) electrocatalysts, suggesting its promising application as an efficient electrode for OER.

In this paper, it is found that the preferential growth of secondary {117} facets of Bi

In this work, N-methyl-2-pyrrolidonium (NMP) was acidized using hydrochloric acid to obtain [Hnmp]Cl first, which was then reacted with FeCl3 to prepare a series of inexpensive tunable [Hnmp]Cl·xFeCl3 (x = 0.2–2.0) ionic liquids (ILs) for the extractive and oxidative desulfurization of model oils. The Lewis acidities of these ILs were tested by the Fourier transform infrared (FT-IR) method, which indicated that when the x value of [Hnmp]Cl·xFeCl3 was above 1.0, the ILs exhibited Lewis acidity. The extraction results showed that the acidification of NMP reduced its dissolubility ability toward dibenzothiophene (DBT) and its Lewis acidity played a determining role in extractive desulfurization. In the catalytic oxidation removal process of the DBT model oil in the presence of H2O2, electron paramagnetic resonance (EPR) and scavenger experiments showed that the hydroxyl radical (˙OH) plays a key role and the superoxide anion radical (O2˙−) has a minor function. [Hnmp]Cl·1.5FeCl3 IL showed excellent recycling performance, which was due to its high dissolving capacity (23 700 ppm) for dibenzothiophene-sulfone (DBTO2).

The main process of carbon dioxide (CO2) photoreduction is that excited electrons are transported to surface active sites to reduce adsorbed CO2 molecules. Obviously, electron transfer to the active site is one of the key steps in this process. However, current catalysts for CO2 adsorption, activation, and electron reduction occur in different locations, which greatly reduce the efficiency of photocatalysis. Herein, through a spontaneous chemical redox approach, the plasmonic photocatalysts of Au-BiOCl-OV with enhanced interfacial interaction were fabricated for visible light CO2 reduction through the simultaneous adsorption, activation and in situ reduction of CO2 without a sacrificial agent. By loading gold (Au) on the oxygen vacancy (OV), Au and BiOCl-OV formed a direct and tight interface contact, whose fine structure was confirmed by SEM, TEM, EPR and XPS, which not only effectively boosts the light utilization efficiency and the light carrier separation ability, but also can simultaneously adsorb, activate and in situ reduce carbon dioxide for highly efficient visible light photocatalysis. Thanks to the synergistic influence of Au and OV, Au-BiOCl-OV exhibits excellent photocatalytic performance without sacrificial agent and outstanding stability with a high CO and CH4 production yield, reaching 4.85 μmol g-1 h-1, which were 2.8 times higher than C-Au-BiOCl-OV (obtained by traditional NaBH4 reduction). This study proposes a new strategy for the production of high-performance collaborative catalysis in photocatalytic CO2 reduction.

Constructing heterojunctions would result in the change of valence band position, which is an important factor determining the oxidative ability of photo-induced holes, has received scant attention. In this paper, β-Bi

Methane is a greenhouse gas that contributes to global warming. Hence, effectively removing the low concentration (1000 ppm) of methane in the environment is an issue that deserves research in the field of catalysis. In this study, oxygen-magnesium bivacancies are simultaneously imbedded into MgO by designing an in situ reduction combustion atmosphere for oxygen release and substituting magnesium with carbon to induce the formation of magnesium vacancies. The DFT calculations reveal that the surface electron density of MgO is improved by the oxygen vacancy structure and the substitution of Mg by C in bulk; this accelerates migration of the charge from the material surface to the adsorbed oxygen species, which leads to abundant surface peroxide species that enable activation and oxidation of methane at a low temperature (below 200 °C). This work could provide a concept for developing non-noble or transition metal oxides for low-temperature activation and conversion of alkanes in the thermocatalytic field through reactive oxygen species.

Heterostructured Bi3O4Br/α-Bi2O3 nanocomposites are prepared via in situ one-step self-combustion of ionic liquids. Tetrabutylammonium bromide (TBAB) is employed to be fuel, complexing agent for ionic liquids, as well as the reactant supplying Br for the objective material. The ratio of Bi3O4Br/α-Bi2O3 can be easily adjusted by controlling the amount of TBAB. The heterojunctions show higher photocatalytic ability towards both azo dye methyl orange (MO) and colorless pollutant phenol. The electron spin resonance (ESR) test and p-nitro blue tetrazolium chloride (NBT) degradation result indicate that generation amounts of superoxide anion radicals ( O2−) over heterojunctions are less than that over pure Bi3O4Br. Photoelectrochemical measurements show that separation efficiencies of photo-generated electrons and holes are decreased after the combination of Bi3O4Br and α-Bi2O3. Work function test and scavenger experiments display that holes play key role for pollutant degradation and the position of holes on α-Bi2O3 is lowered via hybridization. Thus, the enhanced photocatalytic activity over composites can be attributed to the position decline of α-Bi2O3 valence band, thus improving the reactivity of holes in direct oxidation of pollutants. In this case, valence band position is confirmed to be more important than separation efficiency of charge carriers in affecting photocatalytic performance.

In layered Bi-O-X materials, {001} and {110} facets are regarded to be highly active. However, dominant facets in bismuth-rich materials are rarely studied so far. In this paper, the role of main {314} facet of Bi5O7I is investigated for the first time. Bi5O7I samples with adjustable {314} and {008} facet ratios are synthesized using ionic liquid self-combustion method. The inducing growth role of tetramethylammonium iodide for {314} main facet is revealed. Photocatalytic experiments indicate that the activity of Bi5O7I material with {314}/{008} facet ratio of 4.32 are lower than those of Bi5O7I with facet ratio of 5.23 and 4.56, implying the increase of {008} facet proportion could not effectively improve the redox performance. Meanwhile, the controllable oxygen vacancy concentration can be realized by constructing reduction atmosphere. Photoelectrochemical test results show that the synergistic effect of facet ratio and the oxygen vacancies lead to the improvement of charge carriers.

The mismatches of lattices and energy bands in heterojunction are the dominant factors restricting the generation efficiency of reactive oxygen species (ROS) that are powerful tools for water purification and anti-bacteria. In this paper, the mediated lattice matching role of amorphous Al 2 O 3 is presented for constructing the ternary g-C 3 N 4 /Al 2 O 3 /ZnO heterojunctions, which exhibit higher molecular oxygen activation performance than binary g-C 3 N 4 /ZnO and g-C 3 N 4 /Al 2 O 3 heterojunctions. The oxygen activation ability and the ROS generation were testified by the electron paramagnetic resonance (EPR) measurement, transformation of nitroblue tetrazolium (NBT) and degradation of methylene blue (MB). The ROS include superoxide anion radical ( O 2 − ) and consequent product of hydroxyl radical ( OH). The superior oxygen activation performance of the ternary heterojunctions can be attributed to the lattices matching of the mediated amorphous Al 2 O 3 and the resultant efficient cascade electron transfer.

Developing inexpensive photocatalysts is of great value for industrial applications. In the work, magnesia–alumina spinel (MgAl2O4) made from earth-abundant elements is synthesized via a simple hydrothermal route and subsequent calcination. Theoretical calculation indicates that pure MgAl2O4 crystal has an energy band gap of 7.505 eV, and that the top of the valence band is mainly formed by hybridization between Mg-p and O-p states, while the bottom of the conduction band mainly originates from the Mg-s/p and O-s/p states. The UV-vis DRS results show that MgAl2O4 containing amorphous matter absorbs ultraviolet light with a band gap of 3.90 eV, which arises from the longer Mg–O bond length and presence of defects. This research also confirms that the visible-light photocatalytic activity reported in a previous paper is derived from the nitrogen element doping. The photocatalytic activity of MgAl2O4 is evaluated via the decomposition of methylene blue (MB) under UV-vis light illumination. The electron transfer route and the photocatalytic mechanism of MgAl2O4 for degrading MB are proposed. For the first time, the potentials of the energy bands of MgAl2O4 are obtained using Mott-Schottky electrochemical measurement.

Constructing heterojunctions would result in the change of valence band position, which is an important factor determining the oxidative ability of photo-induced holes, has received scant attention. In this paper, β-Bi2O3/Bi2O2CO3 composites with different ratios were obtained via ionic-liquid-assisted solvothermal and in-situ calcination processes. UV-vis DRS, Mott-Schottky test, and Kelvin probe measurement showed the change of band gaps of β-Bi2O3 and Bi2O2CO3 before and after heterojunction formation. SPV, ESR, photocurrent, and scavenger experiments identified the separation efficiency of photo-generated electrons and holes, as well as the active species generated in the photocatalytic process. The photocatalytic mechanism was investigated by the degradation of Rhodamine B (RhB) upon visible-light and simulated sunlight, respectively. The results demonstrated that β-Bi2O3/Bi2O2CO3 heterojunctions possessed enhanced separation efficiency and higher degradation ability than the individuals under visible-light irradiation due to effective electron transfer. However, lower performance under simulated sunlight was observed, although their separation efficiency remained high. The decisive reason for this was that the up-shift of valence band of Bi2O2CO3 induced by hybridization and the transition of holes from VB of Bi2O2CO3 to that of β-Bi2O3 with more negative potential decreased the oxidative ability of holes, which surpassed the positive influence of enhanced separation efficiency.

Synchronous strategy of nanocrystallization and surface modification for g-C 3 N 4 was developed via a facile hydrothermal route in ammonium hydroxide solution. The characterization results reveal that the tailored sample possesses not only an irregular porous structure, higher BET specific surface area, larger band gap, but also rich surface H-bond network. The photocurrent responses and electrochemical impedance spectroscopy indicate that the modification process by ammonium hydroxide via hydrothermal reaction can also accelerate the interfacial charge transfer and improve the separation efficiency of photogenerated charges. As a result, the photocatalytic hydrogen generation rate of tailored g-C 3 N 4 is 4.2 times that of bulk g-C 3 N 4 .

Porous sphere-like tricobalt tetraoxide (Co3O4)-cobalt chloride hydrate (CoCl2·6H2O, CCH) heterojunctions are obtained using a one-step facile solution combustion route. The heterostructure is confirmed by XRD, HRTEM, and XPS measurements. Their photocatalytic performances are evaluated by the degradation of methyl orange (MO) and the reduction removal of Cr(VI) ions under visible light irradiation. The heterojunction containing 81.5 wt% Co3O4 and 18.5 wt% CCH exhibits the highest photocatalytic performance, for which the pseudo-first-order reaction rate constant is 10.0 and 8.7 times that of pure Co3O4 towards MO degradation and Cr(vi) reduction, respectively. This enhancement in activity can be attributed to the effective electron transfer from the conduction band of Co3O4 to that of CCH, which is verified with a double increase of the photocurrent valve of the heterojunction sample electrode in comparison with the bare Co3O4 sample electrode. Electron paramagnetic resonance, fluorescence spectrophotometry and scavenger experiments indicate that photo-induced holes, and hydroxyl and superoxide anion radicals are the active species responsible for the photo-oxidation of MO. The reasons for the formation of these species are discussed and proposed based on the band gap structures of Co3O4 and CCH. The recycling experiment results indicate that the activity can be regained by a remedial experiment.

{001} facet-exposed BiOCl with surface oxygen vacancies (SOVs) is developed via a facile ionic liquid (IL) self-combustion route using diethylamine hydrochloride (DLH, (C2H5)2NH·HCl) as a fuel and a source of the IL cation. It is found for the first time that an excess of DLH can not only facilitate the growth of {001} facets, but also create a reducing atmosphere for combustion, resulting in the release of oxygen atoms on the surface of BiOCl and thus the formation of SOVs. The existence of SOVs lifts the energy band potentials of BiOCl and narrows its energy band gap. To improve the separation efficiency of the photo-generated electrons and holes in BiOCl, amorphous Al2O3 is introduced to construct a heterojunction via an in situ combustion strategy by mixing their aqueous precursors. The heterostructured BiOCl/Al2O3 photocatalysts exhibit noticeable molecular oxygen activation and photocatalytic degradation of Rhodamine B. The conduction band (CB) position of amorphous Al2O3 is proposed for the first time, which matches well with that of BiOCl with SOVs and contributes to the effective transfer of electrons from BiOCl to Al2O3.

Core-shell heterostructured BiVO4@Fe2O3 photocatalysts are fabricated through a facile solution combustion and in-situ precipitation methods. Transmission electron microscopy (TEM) and high-resolution TEM (HRTEM) images verify their core-shell structure. X-ray photoelectron spectroscopy (XPS) results indicate there are interaction between BiVO4 and Fe2O3, confirming the formation of heterojunction. Mott–Schottky measurements exhibit that hybridizing with Fe2O3 makes the conduction band of BiVO4 to be shifted up by 1.05 V from 0.21 to −0.84 V, which endows BiVO4 to be effective for photocatalytic H2 generation. Meanwhile, photoluminescence spectra show that the heterosturcture decreases the recombination efficiency of photo-induced electrons and holes. Hydrogen experiments indicate that BiVO4@Fe2O3 composite containing 10 wt% Fe2O3 has the highest catalytic activity. Keywords: BiVO4/Fe2O3 heterojunction, Solution combustion synthesis, Hydrogen production, Core-shell structure, Visible-light photocatalysis

Heterojunctions of g-C3 N4 /Al2 O3 (g-C3 N4 =graphitic carbon nitride) are constructed by an in situ one-pot hydrothermal route based on the development of photoactive γ-Al2 O3 semiconductor with a mesoporous structure and a high surface area (188 m(2) g(-1) ) acting as electron acceptor. A structure modification function of g-C3 N4 for Al2 O3 in the hydrothermal process is found, which can be attributed to the coordination between unoccupied orbitals of the Al ions and lone-pair electrons of the N atoms. The as-synthesized heterojunctions exhibit much higher photocatalytic activity than pure g-C3 N4 . The hydrogen generation rate and the reaction rate constant for the degradation of methyl orange over 50 % g-C3 N4 /Al2 O3 under visible-light irradiation (λ>420 nm) are 2.5 and 7.3 times, respectively, higher than those over pristine g-C3 N4 . The enhanced activity of the heterojunctions is attributed to their large specific surface areas, their close contact, and the high interfacial areas between the components as well as their excellent adsorption performance, and efficient charge transfer ability.

Novel Al2O3/g-C3N4 heterojunction photocatalysts were fabricated through ultrasonic dispersion method. Al2O3, obtained via solution combustion, contained amorphous ingredient with lots of defect sites and was used as active component for transferring photo-induced electrons of g-C3N4. G-C3N4 was grafted surface hydroxyl groups in the presence of ammonia aqueous solution to combine with Al2O3 possessing positive charges via hydrogen bond. The XRD, SEM, element map, TEM, HRTEM, FT-IR, and XPS results indicate that these synthesized materials are two-phase hybrids of Al2O3 and g-C3N4 with interaction. The photocatalytic results for the degradation of rhodamine B (RhB) indicate that the most active heterojunction proportion is 60wt.% g-C3N4:40wt.% Al2O3, the visible light photocatalytic activity of which is 3.8 times that of a mechanical mixture. The enhanced performance is attributed to the high separation efficiency of photo-induced electrons from the LUMO of g-C3N4 injected into the defect sites of Al2O3, which is verified by photoluminescence spectroscopy (PL) and surface photovoltage (SPV) measurements. The electron paramagnetic resonance (EPR) signals and radical scavengers trapping experiments reveal holes (h(+)) and superoxide anion radical (O2(-)) are the main active species responsible for the degradation of RhB.

A Ti species modified g-C3N4 photocatalyst was synthesized via an in situ hydrothermal route and the subsequent low-temperature calcination. The hydrothermal process results in not only the fabrication of TiO2/g-C3N4 heterojunctions, but also the coordination between Ti species and g-C3N4, which are verified by X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). The electrical resistance test confirms that the coordination can improve the electrical conductivity of composites and can make the charge transfer easier. The photoluminescence (PL) and photocurrent measurements exhibit that the hybridization enhances the separation efficiency of photo-induced electrons and holes. As a result, the Ti species modified g-C3N4 photocatalysts exhibit much higher photocatalytic H2 evolution than the simple heterojunction of TiO2/g-C3N4 obtained via a microwave method and the mechanical mixture of TiO2 and g-C3N4 under visible-light irradiation. The coordination mechanism and synthesis route of TiO2/g-C3N4 heterojunctions are proposed.

Heterostructured BiOBr/Bi24O31Br10 nanocomposites with surface oxygen vacancies are constructed by a facile in situ route of one-step self-combustion of ionic liquids. The compositions can be easily controlled by simply adjusting the fuel ratio of urea and 2-bromoethylamine hydrobromide (BTH). BTH serves not only as a fuel, but also as a complexing agent for ionic liquids and a reactant to supply the Br element. The heterojunctions show remarkable adsorptive ability for both the cationic dye of rhodamine B (RhB) and the anionic dye of methylene orange (MO) at high concentrations, which is attributed to the abundant surface oxygen vacancies. The sample containing 75.2% BiOBr and 24.8% Bi24O31Br10 exhibits the highest photocatalytic activity. Its reaction rate constant is 4.0 and 9.0 times that of pure BiOBr in degrading 50 mg L(-1) of RhB and 30 mg L(-1) of MO under visible-light (λ400 nm) irradiation, respectively, which is attributed to the narrow band gap and highly efficient transfer efficiency of charge carriers. Different photocatalytic reaction processes and mechanisms over pure BiOBr and heterojunctions are proposed.

Mesoporous γ-Al2O3 with high surface area (159 m2/g) is prepared via a precipitation method. The as-synthesized Al2O3 exhibits optical absorption ability in the ultraviolet region and is used as the active component to be combined with g-C3N4 to form effective heterostructured photocatalysts. This heterojunction structure is confirmed by X-ray diffraction, scanning electron microscopy, element map, transmission electron microscopy, high-resolution transmission electron microscopy, Fourier transform infrared, and X-ray photoelectron spectroscopy measurements. The photocatalytic performances of the composites are evaluated by the degradation of rhodamine B (RhB) and methyl orange (MO). Among the prepared photocatalysts, 2g-C3N4:1Al2O3 (weight ratio) exhibits the highest photocatalytic activity, the reaction rate constant of which is 2.5 and 3.7 times that of pure g-C3N4 in degradation of RhB and MO, respectively. The enhancement in activity of heterojunctions is ascribed to their high specific surface areas...

Seeking a simple and moderate route to generate reactive oxygen species (ROS) for antibiosis is of great interest and challenge. This work demonstrates that molecule transition and electron rearrangement processes can directly occur only through chemisorption interaction between the adsorbed O2 and high-energy {111} facet-exposed MgO with abundant surface oxygen vacancies (SOVs), hence producing singlet oxygen and superoxide anion radicals without light irradiation. These ROS were confirmed by electron paramagnetic resonance, in situ Raman, and scavenger experiments. Furthermore, heat plays a crucial role for the electron transfer process to accelerate the formation of ·O2–, which is verified by temperature kinetic experiments of nitro blue tetrazolium reduction in the dark. Therefore, the presence of oxygen vacancy can be considered as an intensification of the activation process. The designed MgO is acquired in one step via constructing a reduction atmosphere during the combustion reaction process, whic...

A series of novel β-Bi 2 O 3 -NiO/Ni heterojunctions were synthesized via one-step solution combustion method and characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), UV–vis spectroscopy and terephthalic acid (TA) fluorescence. The obtained NiO/Ni samples showed visible light absorbance ability and had narrow band gap of ca. 2.20 eV. The coupling of β-Bi 2 O 3 with NiO/Ni promoted the visible light catalytic performance. The enhanced activity could be ascribed to the increase of separation efficiency of electrons and holes and the existence of metallic Ni, which might show a plasmonic effect and could increase the light absorption ability. The scavengers’ tests demonstrated that hydroxyl radical and holes species played a major role for the methyl orange degradation. Furthermore, the as-obtained samples had magnetic properties and could be recycled easily by magnetic separation from the reaction system. Finally, the mechanism of the photocatalytic reaction over β-Bi 2 O 3 -NiO/Ni composites was proposed.

A facile and fast method was developed for the preparation of novel BiOCl/Bi 24 O 31 Cl 10 heterojunctions via a self-combustion of ionic liquids (ILs) route. The ILs were prepared from Bi(NO 3 ) 3 ·5H 2 O and diethylamine hydrochloride ((C 2 H 5 ) 2 NH·HCl). The photocatalysts were obtained by heating the ILs to combustion. In the ILs system, (C 2 H 5 ) 2 NH·HCl serves not only as the source of cation in IL, but also as the main fuel. The prepared composites exhibit noticeable visible light photocatalytic activity in the degradation of organic pollutants, including anionic dye methyl orange and cationic dye rhodamine B, which is attributed to the narrow band gap (2.3 eV) and the effective electrons transfer from the conductive band of Bi 24 O 31 Cl 10 to that of BiOCl, improving the separation efficiency of the photo-generated electron/hole pairs. The heterojunction containing 60.4% BiOCl and 39.6% Bi 24 O 31 Cl 10 exhibits the highest photocatalytic activity. The heterojunction shows dramatic adsorption performance for cationic dye rhodamine B because of its surface negative charges. The radical scavengers result shows that hole is the main reactive species responsible for the degradation of pollutants and superoxide radials are also involved in the photocatalytic process. The results obtained may provide a new sight for broadening the application of ILs in the preparation of nanomaterials and for the in-situ one-step synthesis of heterostructural materials.

A facile and green method was developed for the simultaneous doping of nitrogen, boron, and fluorine in TiO 2 by H 2 TiO 3 via a microwave-assisted route. The ionic liquid (IL) [BMIm]BF 4 serves not only as microwave absorbent but also as a dopant. The IL also shows the ability to self-assemble under microwave irradiation, which causes it to act as an inhibitor for the growth of the TiO 2 particles. The N–B–F-tri-doped TiO 2 obtained exhibits large specific surface area, small crystal size, and a mesoporous structure, and the mechanism for the formation of the N–B–F-tri-doped TiO 2 was proposed. The prepared materials exhibit excellent visible light photocatalytic activity in the degradation of organic pollutants, including methyl orange, rhodamine B, Orange G, and reactive red X, which is attributed to the presence of a Ti–B–N structure on the TiO 2 surface, inducing a narrow band gap of 2.78 eV, and the synergistic effects of N, B, and F, which improve the separation efficiency of the photo-generated electron/hole pairs. The results obtained may provide a new sight for the application of ILs in the microwave-assisted preparation of nanomaterials.

Novel BiOCl–C3N4 heterojunctions were synthesized through an in situ ionic-liquid-assisted solvent-thermal method, through which a highly dispersed heterointerface was formed with almost no loss of C3N4. The composites were characterized using X-ray diffraction, high-resolution transmission microscopy, scanning electron microscopy, nitrogen adsorption–desorption measurements, UV–visible light diffusion reflectance spectrometry, Fourier-transform infrared spectroscopy, and photoluminescence spectroscopy. The results indicated that BiOCl was dispersed on C3N4 to form heterojunction structures with high specific surface area and the ability to absorb visible light. The photocatalytic results for the degradation of methyl orange (MO) indicated that the most active heterojunction proportion is 1BiOCl:1C3N4, which increased the visible light photocatalytic activity 3.3-fold relative to that of a sample of the mechanically mixed counterpart of this composition. The enhanced performance was induced by the high separation efficiency of photoinduced electrons from the LUMO of C3N4 injected into the CB of BiOCl. We also determined that the enrichment of holes in the HOMO of the C3N4 in the present BiOCl–C3N4 heterojunctions played a dominant role in the oxidation of MO.

An in situ microwave-assisted synthesis approach has been developed to prepare N-TiO2/g-C3N4 composites using H2TiO3 as the reactant and NH3·H2O as the N-doping source. In this way, the N-TiO2/g-C3N4 composite catalysts have a porous structure and large surface areas, which increase the contact area of pollutants. Degradation of rhodamine B (Rh B) and methylene blue (MB) were carried out to evaluate the photocatalytic activity of samples under visible light irradiation. N-TiO2/g-C3N4 composite with 40 wt % N-TiO2 exhibits the highest photocatalytic activity and the optimal temperature is 400 °C. The increased photocatalytic activity of N-TiO2/g-C3N4 composites can be attributed to the formation of the heterojunction between N-TiO2 and g-C3N4, which suppresses the recombination of photoinduced electron–hole pairs. The tests of radical scavengers confirmed that •O2– was the main reactive species during the photocatalytic process.

A novel approach of SBA-15 mesoporous materials decorated with various amounts of TiO2 (10–30% TiO2/SBA-15) were prepared by the post-synthesis method using metatitanic acid as precursor and template-retentive SBA-15 as support. The result shows that the silica framework was stable and it was almost not affected by appropriate titania deposition. The photocatalytic activity of the samples was tested by degradation of methyl orange (MO), which was increased with increasing TiO2 loading ratio at first and then decreased. The 17% TiO2/SBA-15 composite calcinated at 600 °C showed the highest photocatalytic ability for degradation of MO because of its appropriate amount of TiO2 and less agglomeration.

Surface defect of nanomaterials is an important physical parameter which significantly influences their physical and chemical performances. In this work, high concentration of surface oxygen vancancies (SOVs) are successfully introduced on {001} facets exposed BiOBr nanosheets via a simple surface modification using polybasic carboxylic acids. The chelation interaction between carboxylic acid anions and Bi3+ results in the weakness of Bi-O bond of BiOBr. Afterwards, under visible-light irradiation, the oxygen atoms would absorb the photo-energy and then be released from the surface of BiOBr, leaving SOVs. The electron spin resonance (ESR), high-resolution transmission electron microscopy (HRTEM) and UV–vis diffuse reflectance spectra (DRS) measurements confirm the existence of SOVs. The SOVs can enhance the absorption in visible light region and improve the separation efficiency of photo-generated charges. Hence, the transformation rate of adsorbed O2 on the as-prepared BiOBr with SOVs to superoxide anion radicals (•O2−) and the photocatalytic activity are greatly enhanced. Based on the modification by several carboxylic acids and the photocatalytic results, we propose that carboxylic acids with natural bond orbital (NBO) electrostatic charges absolute values greater than 0.830 are effective in modifying BiOBr.

Nitrogen-doped Degussa P25 TiO 2 –amorphous Al 2 O 3 composites were prepared via facile solution combustion. The composites were characterised using X-ray diffraction, high-resolution transmission microscopy, scanning electron microscopy, nitrogen adsorption–desorption measurements, X-ray photoelectron spectroscopy, UV–vis light-diffusion reflectance spectrometry (DRS), zeta-potential measurements, and photoluminescence spectroscopy. The DRS results showed that TiO 2 and amorphous Al 2 O 3 exhibited absorption in the UV region. However, the Al 2 O 3 /TiO 2 composite exhibited visible-light absorption, which was attributed to N-doping during high-temperature combustion and to alterations in the electronic structure of Ti species induced by the addition of Al. The optimal molar ratio of TiO 2 to Al 2 O 3 was 1.5:1, and this composite exhibited a large specific surface area of 152 m 2 /g, surface positive charges, and enhanced photocatalytic activity. These characteristics enhanced the degradation rate of anionic methylene orange, which was 43.6 times greater than that of pure P25 TiO 2 . The high visible-light photocatalytic activity was attributed to synthetic effects between amorphous Al 2 O 3 and TiO 2 , low recombination efficiency of photo-excited electrons and holes, N-doping, and a large specific surface area. Experiments that involved radical scavengers indicated that OH and O 2 − were the main reactive species. A potential photocatalytic mechanism was also proposed.

Nano-TiO2 was prepared in [Bmim]BF4 ionic liquid (IL) via microwave radiation. The [Bmim]BF4 IL that contained the as-prepared TiO2 was mixed with dibenzothiophene (DBT) in n-octane, which was used as model oil for photocatalytic desulfurization under the UV irradiation. In this process, IL was used not only as microwave absorption medium for preparation of TiO2 but also as extractant for DBT. The effect of microwave time on the photocatalytic desulfurization ability of prepared TiO2 in the presence of O2 was investigated. 98.2% and 94.3% sulfur could be removed from model oil and actual diesel oil, respectively, in 10 h UV irradiation under the conditions that V(IL)/V(oil) = 1:5, air flow = 200 mL/min. The [Bmim]BF4 IL was recycled five times with a slight decrease in desulfurization efficiency.

A new C5H9NO·SnCl2 coordinated ionic liquid (IL) was prepared by reacting N-methyl-pyrrolidone with anhydrous SnCl2. Desulfurization of dibenzothiophene (DBT) via extraction and oxidation with C5H9NO·SnCl2 IL as extractant, H2O2 and equal mol of CH3COOH as oxidants was investigated. The Nernst partition coefficients kN of C5H9NO·SnCl2 IL for the DBT in n-octane was above 5.0, showing its excellent extraction ability. During the oxidative desulfurization process, the optimal molar ratio of H2O2/DBT was six. Sulfur removal of DBT in n-octane was 94.8% in 30 min at 30 °C under the conditions of H2O2/DBT molar ratio of six and V (IL):V (oil) = 1:3. Moreover, the sulfur removal increased with increasing temperature because of the high reaction rate constant, low viscosity, and high solubility of dibenzothiophene-sulfone in the IL. The kinetics of oxidative desulfurization of DBT was also investigated, and the apparent activation energy was found to be 32.5 kJ/mol. The IL could be recycled six times without a significant decrease in activity.

Mixed amorphous and crystalline MgAl2O4 nanopowders with visible light-induced photocatalytic activity were prepared via a simple solution combustion method using glycine and urea as fuel mixtures. The obtained samples were characterized by X-ray diffraction, field emission scanning electron microscopy, energy-dispersive X-ray, transmission electron microscopy, Brunauer–Emmett–Teller (BET) surface area, thermogravimetry, X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, and UV–Vis diffuse reflection spectrum. The results showed that the combustion was almost complete, the crystallinity and crystallite size of MgAl2O4 increased with the increase of fuels, and there was N atoms doped in the catalysts. The MgAl2O4 containing amorphism had photo-absorption ability in visible light region. The photocatalytic results for degradation of methylene blue (MB) indicated that the combustion-synthesized samples had photocatalytic activity, whereas the annealed well crystalline MgAl2O4 nanopowders had none. The MgAl2O4 sample containing about 45.6% crystalline and 55.4% amorphous materials showed the highest photocatalytic activity, with a 99.5% MB removal in 100 min under visible light irradiation. The fluorescence spectra verified that the greater the formation rate of OH radicals, the higher the photocatalytic activity achieved.

Nano-TiO2 modified by ionic liquid was prepared by sol-gel method with Ti(OC4H9)4 as titanium source. The chemical structure of the nanopartical was characterized by X-ray powder diffraction (XRD), transmission electron microscopy (TEM) and UV-Vis diffuse reflectance spectra (UV-Vis DRS). The results indicated that the modified TiO2 was almost entirely small nanocrystal and multihole and had high crystallinity. Radius of the modified particals had some degeree of reduction than that of the pure TiO2. The optical absorptivity of modified TiO2 is stronger than that of unmodified TiO2. The photocatalytic degradation activity of methylene blue with the prepared TiO2 was investigated. The degradation rate could reach more than 88%.

The synthesis of NdFeO3 perovskites in a reverse microemulsion and its photocatalytic property for visible light degradation reaction of methylene blue were investigated, respectively. When the irradiation time prolonged from o to 90 minutes, the degradation rate for methylene blue could achieve 60%. XRD pattern shows that a well-crystallized perovskite structure is observed for the NdFeO3 sampled prepared. The TEM characterization result indicates that the dimension of NdFeO3 nanopowders is in the range of 35~45 nm, which is consistent with the calculation result using the Scherrer equation.

Nano-titanium dioxide (TiO2) was synthesized by sol-gel method and was used as photocatalyst for photocatalytic oxidation desulfurization of fuel oil. Et3NHCl·FeCl3 was synthesized as low-viscosity ionic liquid (IL) and used as efficient extractant and oxygen in air was used as oxidant. Nano-TiO2 was analysis by X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FT-IR). The factors influencing the desulfurization rate of model oil such as oil ratio, the amount of titanium dioxide, the air pass into the volume and photocatalytic time. The results show that the desulfurization rate could reach 98.5% in 3h under below conditions: TiO2 amount was 0.1g/100mL, air flow was 500 ml / min and V(IL):V(oil)=1:1.

A series of well-structured α-Bi2O3/Bi2WO6 heterojunctions was successfully prepared via an in situ one-step solution combustion method. HRTEM result indicated that there were many heterostructure interfaces formed in the as-obtained composites. The rhodamin B degradation results showed that the heterojunctions exhibited higher activities than those of pure α-Bi2O3 and pure Bi2WO6 under visible light irradiation. The enhanced performance was attributed to effective electrons transfer from α-Bi2O3 to Bi2WO6 and was also demonstrated by the photoluminescence test. Finally, a possible charge separation process mechanism over the α-Bi2O3/Bi2WO6 heterojunction was proposed.