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Heterojunction photocatalytic materials show excellent performance in degrading toxic pollutants. This study investigates the influence of calcination temperature on the performances of floral Bi2O3/TiO2 composite photocatalyst crystal, which was prepared with glycerol, bismuth nitrate, and titanium tetrachloride as the major raw materials via the solvothermal method. XRD, SEM/TEM, BET, Uv-vis, and XPS were employed to analyze the crystal structure, morphology, specific surface area, band gap, and surface chemical structure of the calcined temperature catalysts. The calcination temperature influence on the catalytic performance of composite photocatalysis was tested with rhodamine B (RhB) as the degradation object. The results revealed the high catalytic activity and higher photocatalytic performance of the Bi2O3/TiO2 catalyst. The degradation efficiency of the Bi2O3/TiO2 catalyst to RhB was 97%, 100%, and 91% at 400 °C, 450 °C, and 500 °C calcination temperatures, respectively, in which the peak degradation activity appeared at 450 °C. The characterization results show that the appropriate calcination temperature promoted the crystallization of the Bi2O3/TiO2 catalyst, increased its specific surface area and the active sites of catalytic reaction, and improved the separation efficiency of electrons and holes. [ABSTRACT FROM AUTHOR]

An investigation on TiO 2 /SiO 2 catalysts was performed, covering a wide range of TiO 2 contents (0–100 % wt%) and calcination temperatures (150–1000 °C), which were applied to a continuous gas-solid photocatalytic reactor, irradiated by UV-LED for n -hexane degradation. A series of characterization analyses were conducted and the effects of the operational parameters and the catalyst stability over time were investigated. The TEM images confirmed the results of XRD crystallography, showing the preferential (101) anatase plane, in the form of 4–5 nm nanocrystals. Silica gel delayed the phase transformation from anatase to rutile even after calcination at 750 °C, while the band gap energy decreased from 3.21 to 3.06 eV with increasing calcination temperature from 150 to 1000 °C. The 20 %-TiO 2 material calcined at 450 °C exhibited the best performance among 14 different materials, reaching a conversion rate of 2.7 × 10−7 mol g−1 min−1, n -hexane degradation of 40 %, maintaining its stability even after 20 h of continuous photoreaction, with resistance to TiO 2 leaching and particle breakage. Therefore, the presence of silica significantly enhanced the properties of the catalyst, and contributed to improving its photocatalytic activity, making the use of these materials in gas-solid photoreactors a viable alternative for removing volatile organic compounds. [Display omitted] • 450 °C was the ideal calcination temperature in the range of 150–1000 °C. • The transition from anatase to rutile changed to above 700 °C. • SiO 2 support increases the photoactivity of TiO 2 in a fluidized bed reactor. • The catalyst showed high stability over 20 h of n -hexane photocatalytic degradation. [ABSTRACT FROM AUTHOR]

Titanium dioxide (TiO2) nanoparticles were synthesised by the modified sol–gel method at different calcination temperatures. Samples were characterized using X-ray diffraction (XRD), high-resolution transmission microscopy, scanning electron microscopy, energy dispersive X-ray analysis (EDAX), Fourier transform infrared (FTIR) spectroscopy, Brunauer, Emmett and Teller surface area analyzer (BET) and diffuse reflectance spectroscopy (DRS). Phase transformation of TiO2 nanoparticles from anatase to rutile phase with an increase in calcination temperature from 573 to 1173 K was observed from XRD analysis. Detailed structural analysis using size–strain plot and Halder–Wagner method was done for all samples. The formation of TiO2 nanoparticles was confirmed from FTIR and EDAX spectra. The TEM image of the sample calcined at 673 K showed non-spherical shaped particles having particle sizes 13.16 ± 3.35 nm. The bandgap energy calculated from DRS decreases with an increase in calcination temperature, which supports phase transformation observed in XRD analysis. The photocatalytic degradation efficiency was evaluated by monitoring the degradation of Congo red (CR) azo dye under UV light and natural sunlight. The degradation of CR dye was confirmed by analysing the FTIR spectrum of the degraded sample. The sample calcined at 673 K, in the pure anatase phase, exhibited the highest photocatalytic activity. [ABSTRACT FROM AUTHOR]

Titanate nanotubes (NTs) were synthesised by the hydrothermal method and later calcined at temperatures between 100–500°C. The calcined NTs were characterised and evaluated in the physicochemical adsorption of the safranin dye and photocatalytic degradation of caffeine. The materials calcined at low temperatures displayed a tubular structure and the H2Ti3O7 crystalline phase, which was transformed into anatase nanoparticles at 400°C. The NTs treated at 100°C showed the highest adsorption capacity (94%). Safranin was adsorbed through an ion-exchange mechanism, following the Langmuir isotherm and a pseudo-second-order kinetic model. While NTs calcined at lower temperatures were better for adsorption, the photocatalytic degradation of caffeine increased in samples calcined at higher temperatures with a maximum removal of 72%. The photocatalytic behaviour of the NT samples confirmed that the crystalline anatase structure in conjunction with structural OH groups enhanced the photocatalytic activity. The addition of isopropanol as a scavenger confirmed the important role played by the •OH radicals in the photocatalytic process. NTs calcined at 300°C were efficient for both adsorption and photocatalytic processes. Due to its efficiency, this sample was reused after dye adsorption for the photocatalytic degradation of caffeine under visible light due to its enhanced absorbance in the visible region. This research work shows the potential of NTs for wastewater purification. [ABSTRACT FROM AUTHOR]

The pharmaceutical industry wastewater (PIW) was treated by successive use of electro Fenton (EF) and photocatalytic oxidation (PcO) processes. Nano-particular powdered Fe/HNT (Iron/Halloysite nanotube) heterogeneous semiconductor catalyst was initially produced with Fe(OH) 3 sludge modification precipitated after EF process. Thus, photocatalyst material was produced from the waste sludge and used in the PcO process. Photocatalyst Fe/HNT powder was immobilized on a three-dimensional (3D) reticulated Al 2 O 3 ceramic support to enable rapid recovery of the catalyst from the PcO reactor system. Particle morphology and chemical configuration of the heterogeneous catalysts were analyzed with SEM (Scanning Electron Microscopy)-EDS (Energy-Dispersive X-ray spectrometry), UV-DRS (Ultraviolet Diffuse Reflectance Spectra) and XRD (X-ray diffraction). The Fe/HNT layer was calcined at three different temperatures (350, 450 and 600 °C). The optimum temperature was determined as 350 °C for better photocatalytic performance and practical reasons such as energy consumption. The successive use of EF + PcO processes for degradation of three different PIW samples was investigated by using two catalyst forms (nanoparticle and reticulated) and light sources (visible and sun light). The max TOC removal efficiency by EF + sun light-PcO (with Fe/HNT) successive treatment process was obtained as 78.4 %. Besides, the energy consumption value was calculated for optimum process state and calculated as 48.8 kWh/kg TOC at the EF + sun light-PcO (with Fe/HNT) successive treatment process. • The nanoparticle Fe/HNT semiconductor heterogeneous catalyst was developed from recycled waste Fe(OH) 3 sludge. • Photocatalyst Fe/HNT powder was immobilized on a three-dimensional (3D) reticulated Al 2 O 3 ceramic support. • Developed Fe/HNT and Fe/HNT-Al 2 O 3 composite semiconductor photocatalysts worked effectively under visible and sun light. • The treatment of PIW was investigated by successive use of electro-Fenton (EF) and photocatalytic oxidation (PcO) processes. • Fe/HNT and Fe/HNT-Al 2 O 3 photocatalysts were utilized for PcO process for successive treatment. [ABSTRACT FROM AUTHOR]

In this study, Co-porous-g-C3N4(porous Co-Doped graphitic carbon nitride) was synthesized by a one-step calcination method successfully. Co-porous-g-C3N4 was characterized by transmission electron microscopy, X-ray photoelectron spectroscopy, UV-vis diffuse reflectance, and specific surface area determination. The Photo- Fenton-like system was successfully constructed under the condition of coexistence of Co-porous-g-C3N4 and H2O2. The synergistic effect of Fenton-like system and photocatalysis was realized. Through the optimization of experimental conditions, the best photocatalytic performance of this heterogeneous reaction system was achieved. The degradation rate of MB (methylene blue, 40 mg/L) could reach 98.3% at 90 min. Co-porous-g-C3N4 had photocatalytic degradation activity for different organic pollutants and had wonderful recyclability and stability. The main degradation effect was attributed to ·O2- which could be generated through two channels in the Photo- Fenton-like system. Moreover, the rate of photogenerated electron-hole complexation could be decreased due to the reaction of low-valent cobalt and photoelectrons in this heterogeneous reaction system. [ABSTRACT FROM AUTHOR]

Titanium ferrite represents one of the most promising magnetic materials that exhibits optical absorption in both ultraviolet and visible spectral regions with a range of applications in photocatalysis, giant magnetoresistance, sensors, high-frequency modern power supplies, etc. Here in the present work, we report synthesizing titanium ferrite NPs via the co-precipitation method. As obtained ferrite nanopowders were characterized using XRD, UV-Visible absorption, Raman scattering, and variable sample magnetometer techniques. The crystalline size of NPs lies between 35 to 50 nm. The as-obtained nanopowder samples were calcined at 200, 500, 800 °C temperatures, and the resulting change in the optical, structural, and magnetic properties are investigated. The saturation magnetization of 500 °C calcined sample is higher than that calcined at 200 °C, but the magnetization value drastically becomes reduced for powder calcined at 800 °C temperature. The results of the present work can be used to understand the effects of annealing temperature on the structural and magnetic properties of other ferrite nanomaterials. [ABSTRACT FROM AUTHOR]

α-Fe2O3 nanoparticles were synthesized via a straightforward method. XRD, FTIR, SEM, ESR, and DRS techniques investigated the influence of various calcination temperatures on the crystal structure, optical, and photocatalytic properties of the samples. The obtained results demonstrated that the average crystallite size increased with the increase in the calcination temperature. Measured and computed optical properties were in accordance and the bandgap energy decreased with the increase in the calcination temperature. The highest photocatalytic degradation efficiency for diclofenac (DCF) was obtained with the sample calcinated at 300 °C (96%). The photocatalytic process occurs because of the presence of OH• radicals. The addition of H2O2 led to the inhibition of OH• radicals that H2O2 scavenged. [ABSTRACT FROM AUTHOR]

[Display omitted] • Study on the photocatalytic performance of TiO 2 composited with Ag 3 PO 4 based on biological template. • Ag 3 PO 4 /TiO 2 is beneficial to the degradation of Rhodamine B. • Ag 3 PO 4 /TiO 2 can improve the electron transfer efficiency of the interface. The hollow tubular structure of kapok fiber was successfully replicated by using kapok fiber as a template through a high-temperature calcination method. The kapok fiber was treated as a photocatalytic carrier material, the photocatalytic performance of the samples that tubular TiO 2 composited with Ag 3 PO 4 prepared by the new method was discussed. It was found that Ag 3 PO 4 particles with small particle size can be prepared through a simple stirring method at room temperature. Ag 3 PO 4 /TiO 2 composite material can be obtained by an in-suit synthesis. The experimental results show that the Rhodamine B can be photodegraded completely by Ag 3 PO 4 /TiO 2 composite within 60 min, the photodegradation of Ag 3 PO 4 /TiO 2 is significantly better than the photocatalytic effect of pristine TiO 2. After three cycles, the degradation rate can still achieve 100% within 60 min. The photogenerated carriers separation efficiency of Ag 3 PO 4 /TiO 2 was improved by composite with Ag 3 PO 4. Through the visible diffuse spectra (DRS), it is obvious that the Ag 3 PO 4 /TiO 2 has strong absorption in the visible spectrum, and the photocatalytic performance of the sample is improved. [ABSTRACT FROM AUTHOR]

Titanium-vanadium oxo-alkoxy (VTOA) nanoparticles with vanadium addition (V:Ti) between 0 and 20 mol% were prepared via sol-gel method in a chemical reactor with ultra-rapid micromixing. A control of the nucleation and growth process in the reactor permitted synthesis of size-selective V-TiO2 nanoparticles, which were used for the nanocoatings deposition on glass beads. The activity of the prepared photocatalysts (after calcination at 450 °C) was studied by the degradation of methylene blue in aqueous solutions under UVA illumination. A steady decrease of the reaction rate was observed with an increase of the vanadium content. This effect was explained by the residual presence of non-crystallized oxide, which elimination requires further studies. [ABSTRACT FROM AUTHOR]

CeVO4 as UV light-driven photocatalyst was synthesized by sol-gel method using tartaric acid as a complexing reagent with subsequent calcination at 450–600 °C for 2 h in ambient air. The as-synthesized products were characterized by thermogravimetric analysis (TGA), X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR), and Raman spectroscopy. The precursor shows two weight loss steps due to the evaporation and decomposition of absorbed water, tartaric acid, and nitrate constituent until at a temperature above 450 °C. XRD patterns of the samples were indexed to tetragonal zircon-type CeVO4 structure. The degree of crystallinity and size of the CeVO4 sample were increased by the high growth rate of CeVO4 nanoparticles at high temperature calcination. Particle sizes of the products were 20–40 nm for CeVO4 with 450 °C calcination and 80–120 nm for CeVO4 with 500 °C calcination. The detection of V–O and Ce–O stretching modes indicates the formation of tetragonal zircon-type CeVO4 structure. The photocatalytic activity of the as-synthesized CeVO4 nanoparticles was evaluated via the degradation of methylene blue (MB) under UV light irradiation. In this research, CeVO4 with 450 °C calcination showed the highest photocatalytic activity of 94.58% within 120 min under UV light irradiation because of the highest available surface active sites for photodegradation of MB under UV light irradiation. [ABSTRACT FROM AUTHOR]

Nano-TiO2 was prepared with butyl titanate as a precursor by sol-gel method. The samples were analysed by TG-DTA, X-ray diffraction, TEM and so on to assess the effects of different temperatures on the crystal structure, grain size, and microstructure of nano-TiO2. Meanwhile, the catalytic effect of heat treatment temperature on the degradation performance of TiO2 to methyl orange was investigated. The dynamic process of grain growth was preliminarily analysed by Eastman’s particle growth theory. The result shows that TiO2 particle size gradually increases with the heat treatment temperature. At 450 to 550°C, the grain is mainly anatase phase, a mixture of anatase and rutile phase was found at 650°C (mass ratio A:R = 9:1), and the degradation rate of nano-TiO2 on methyl orange reaches 97.75%. When the calcination temperature exceeds 850°C, TiO2 particles almost entirely are composed of rutile phase, and the photocatalytic activity decreases significantly. At 730°C, half of the crystalline TiO2 is transformed from anatase to rutile form. The apparent activation energies of the anatase and rutile crystals of nano-TiO2 are 18.15 kJ/mol and 42.56 kJ/mol, and the fastest grain growth occurs at 546°C and 1280°C respectively. [ABSTRACT FROM AUTHOR]

Metal-organic frameworks (MOFs) have received extensive attention, relying on the characteristic of porosity, high specific surface area and modifiability. Its semiconductor characteristics make it focus in the field of photocatalysis. Based on the classification of modification methods, this article summarized the recent researches on MOFs in the field of photocatalysis, including inner confinement metal nanoparticles, semiconductor composites and MOFs derivatives. The first two modifications aim to reduce the recombination of photogenerated electrons and holes by transferring them. The latter removes the partial ligand by calcination and retain the porous structure framework of MOFs, which improve the chemical stability of MOFs. Such MOF-based photocatalysts have been used in the fields of environmental pollution control and energy sustainable development. [ABSTRACT FROM AUTHOR]

Semiconductor photocatalysis technology is one of the ways to control environmental pollution using solar energy. Because of its chemical stability, low toxicity and high photocatalytic oxidation-reduction ability, titanium dioxide has become one of the most widely studied and applied semiconductor photocatalytic materials. However, there are also some problems such as the response only in the ultraviolet range, rapid recombination of electron pairs produced by light during photodegradation, and the small specific surface area. On account of the limitations of titanium dioxide photocatalyst, the key factors and breakthroughs to improve performance new materials, this paper uses g-C3N4 of improving the photocatalytic function of titanium dioxide. Because g-C3N4 has good conductivity, relatively strong adsorption capacity and larger specific surface area compared with other carriers, g-C3N4 is one of the most promising carriers. In this research work, g-C3N4/TiO2 heterogeneous nanocomposites were prepared by combining TiO2 nanowires with g-C3N4. First of all, we need to change the morphology of titanium dioxide. We use high-voltage electrospinning technology to achieve this goal. This method greatly increases the specific surface area and increases the active sites involved in photocatalytic activity. Then, g-C3N4 was prepared with melamine as raw material by high temperature calcination. Then, the hydrothermal method combined with the good characteristics of g-C3N4 enhanced the deflection of photogenerated electrons and prolongs the lifetime of photogenerated electron-hole pairs. The photocatalytic efficiency of nanocomposites is greatly improved Rhodamine B solution was completely degraded in 120 min. [ABSTRACT FROM AUTHOR]

In this work we prepared boron doped TiO2 (B-TiO2) photocatalysts and evaluated their photocatalytic activity for the degradation of our model organic pollutant, 4-nitrophenol (4-NP). The photocatalysts were prepared using wet impregnation method with different calcination times, calcination temperatures and dopant amounts in order to determine the optimum parameters. The degradation of the pollutant was carried out in a specially designed degradation chamber and characterized by UV-Vis spectrophotometry. The degradation kinetics were evaluated with pseudo-first order kinetics by comparing rate constants and half-lives of various photocatalytic reactions. It was found that the highest removal rate was obtained for 0.50 % boron doping with calcination at 450°C for 3 hours. The results showed that TiO2 could be doped with boron, which is in abundance in our country, and used for the photocatalytic degradation of a toxic pollutant in water. The promising results for the organic matter removal could pave the way for further studies of environmental applications. [ABSTRACT FROM AUTHOR]

BiYO 3 powders were synthesized by the Pechini method under low-temperature conditions. When the heat treatment was performed at T < 600 °C, a mixture of tetragonal and cubic phases was obtained, while for T ≥ 600 °C, only the fluorite-like cubic phase was observed. Based on the Rietveld refinement, approximately 2% and 1% of the tetragonal phase remained in samples calcined at 400 °C and 500 °C for 1 h, respectively. The crystal size calculated for these samples was 4.4–48.1 nm, depending on the calcination temperature. The specific surface area of the samples diminished with heat treatment and reached a minimum at 800 °C. The band gap of samples with mixed phases was close to 2.16 eV and was ~2 eV for samples with a cubic phase. Photocatalytic tests demonstrate that BiY 0.995 Ni 0.005 O 3 calcined at 800 °C had the best performance: it degraded more than 80% of the antibiotic oxytetracycline when irradiated with visible light. The Ni-doped BiYO 3 material could degrade the antibiotic in tap water at an environmentally relevant concentration (μg L−1 levels) and showed steady activity throughout four reaction cycles. [ABSTRACT FROM AUTHOR]

We report a facile method for the synthesis of Na+/Ca²+ ions modified TiO2 xerogels by coprecipitation followed by calcination process. The resultant materials are well characterized by powder X-ray diffraction, Raman spectroscopy, ultraviolet-visible diffuse reflectance spectroscopy and high resolution transmission electron microscopy. Presence of sodium and calcium ions can influence the crystallinity of rutile TiO2. The photocatalytic performances of bare rutile TiO2 along with modified materials such as Na-TiO2, Ca-TiO2, Na-Ca-TiO2 materials are evaluated by calculating the amount of hydrogen evolved during the photocatalytic decomposition of water under light irradiation.This study will be effective informulating the effect of alkali/alkaline earth metal ions on the photocatalytic activity of rutile TiO2. [ABSTRACT FROM AUTHOR]

• Zinc ferrite powders with unique topologies were produced by low-oxygen calcination. • The powders gained superiority as efficient photocatalysts to degrade pollutants. • The pseudo-second-order kinetic model was valid for the whole catalytic experiment. It is a general consensus that calcined powders, being of agglomerated microstructure feature and devoid of hydrophilic groups, are not conducive to their aqueous-phase applications including catalytic, environmental and biomedical types. In this work, a facile low-oxygen calcination processing on zinc ferrite was adopted to break this stereotype. Compared with the powder calcined in the air (reference sample), newly produced powders not only possessed distinctive topologies with less conglomeration, but also gained their superiority as more efficient photocatalysts to degrade salicylic acid and phenol. Their pseudo-second-order degradation constants were about 1.4 and 1.8 times larger than that of the reference sample in photo degrading salicylic acid and phenol, respectively. Such a low-oxygen calcination technique features the merits of low cost, easy operation and versatility for any other metal oxides. Thus, it is anticipated that our investigation will shed some new light on mass production of industrial-grade powder without compromising its expected performance in practical application. [ABSTRACT FROM AUTHOR]

Multiferroic YFeO3 nanofibers were prepared by electrospinning. The as-prepared nanofibers were characterized by XRD, TG-DTA, SEM and Raman spectrum. The magnetic property and photocatalytic activity of the orthorhombic YFeO3 nanofibers were also investigated. The results show that the crystal structure and morphology of the YFeO3 nanofibers were influenced by the calcination temperature. Pure orthorhomic YFeO3 nanofibers can be obtained when the temperature increased to 860 °C and they exhibit ferromagnetism with slight antiferromagnetism at room temperature. The degradation test of RhB and MB under simulated sunlight show that the YFeO3 nanofibers possess higher photocatalytic activity, compared with the YFeO3 nanoparticles. [ABSTRACT FROM AUTHOR]

In the present study, we adopted, a green approach for the synthesis of ZnFe2O4 nanoparticles using the aqueous flower extract of Nyctanthes arbor-tristis. This extract served as the reducing agent for the synthesis of ZnFe2O4. The obtained nanoparticles were characterized by X-ray diffraction studies which indicated the formation of single phase ZnFe2O4. The size of the nanoparticles was in the range of 4.5–12 nm with calcination temperature as revealed from X-ray diffraction and Transmission electron microscopy, UV-Visible spectroscopy. Photocatalysis studies were made on RhodamineB dye, to assess the degradation capability of the nanopowders calcined at different temperature. [ABSTRACT FROM AUTHOR]

We report the synthesis of new photoactive carbon nitride polymers with high oxygen content (CNO) at low calcination temperatures (300–400 °C). To do so, we designed new carbon‐ and oxygen‐rich supramolecular assemblies as reactants. The starting monomers' composition allows the formation of photoactive CNO semiconductors with extended absorption and ordered morphologies. Interestingly, at these reaction temperatures, the chemical structure of the starting monomers is partially retained, opening a path for the transfer of properties from the molecular level to the final CN materials after condensation. The new CNO polymers exhibit good photoactivity for the hydrogen evolution reaction, CO2 reduction and rhodamine B dye degradation. [ABSTRACT FROM AUTHOR]

To promote the interaction of p–n semiconductors, raspberry‐like microspheres of core–shell Cr2O3@TiO2 nanoparticles have been fabricated through a five‐step process. Raman spectroscopy of products calcined at various temperatures reveal that the titania shell causes crystal distortion of the Cr2O3 core, without changing the microstructures of the fabricated core–shell microspheres. In situ and time‐resolved synchrotron‐based powder XRD reveals the formation of monoclinic TiO2 in the fourth step, but these monoclinic TiO2 nanocrystals undergo a phase transition when the applied calcination temperature is above 550 °C. As a result, TiO2(B), a magnéli phase of Ti4O7 and Cr2Ti6O15 compounds, resulting from inner doping between Cr2O3 and TiO2, is formed. The close interaction of Cr2O3 and TiO2 forms a p–n junction that decreases the recombination of photogenerated electron–hole pairs, leading to enhanced production of CH4 by photocatalytic reduction of CO2. [ABSTRACT FROM AUTHOR]

CaIn2O4/In2O3 composites were prepared with electrospinning method. The samples were calcined at different temperatures and characterized with XRD, SEM, UV–Vis DRS, N2 adsorption-desorption isotherm, FT-IR and Raman spectroscopy. The effects of calcination temperature on crystal phase, morphology, band gap energy (Eg), BET specific surface area and pore size of the CaIn2O4/In2O3 composites were investigated. The degradation of methyl blue (MB) was used to evaluate the photocatalytic activity of the CaIn2O4/In2O3 composites under the irradiation of simulated sunlight. The results showed significant effect of calcination temperature on crystal phase, morphology and photocatalytic performance of the composites. When calcination temperatures were 700 °C and 1000 °C respectively, the CaIn2O4/In2O3 composites showed nanobelts and nanoparticles with high photocatalytic activity. The degradation rate of MB was 76% and 92% after simulated sunlight irradiation for 120 min for the CaIn2O4/In2O3 composites calcined 700 °C and 1000 °C, respectively. This is attributed to the large specific surface area, the efficient separation and transportation of photogenerated carriers. All the results revealed that the CaIn2O4/In2O3 composites were a promising candidate in the practical application of dye wastewater treatment. [ABSTRACT FROM AUTHOR]

The high-temperature secondary calcination (>500 °C) of bulk g-C 3 N 4 usually suffers from a very low yield of g-C 3 N 4 nanosheets owing to its serious and massive depolymerization. In this study, a NH 4 Cl-induced low-temperature second-calcination approach has been used to synthesize nitrogen-rich g-C 3 N 4 nanosheets with a high yield (ca. 32 wt%), which includes the initial intercalation of NH 4 Cl into the interlayers of bulk g-C 3 N 4 and the following direct low-temperature calcination at 400 °C. It is found that during the calcination process, the thermal gas flow (HCl and NH 3) from NH 4 Cl decomposition not only can efficiently facilitate the delamination and depolymerization of the g-C 3 N 4 structure, but also can introduce many amino groups on the g-C 3 N 4 surface, resulting in the successful synthesis of nitrogen-rich g-C 3 N 4 nanosheets at such a low temperature. Experimental data suggests that the resulting nitrogen-rich g-C 3 N 4 nanosheets show a distinct enhancement for the H 2 -evolution performance mainly owing to the introduction of amino groups, which can efficiently enrich H+ from water to facilitate the rapid generation of H 2. This study may open up a fire-new insight for the preparation of high-efficiency nanometer materials. Image 1 [ABSTRACT FROM AUTHOR]

In this work, different synthesis methods of zinc stannate (Zn2SnO4–ZTO) were proposed in order to obtain a material with a greater porous structure and higher surface area when compared to conventional hydrothermal method. Zn2SnO4 particles were prepared using a conventional oven method (CO), ultrasound (US), microwave (MW) and high pressure Asher (HPA), all followed by calcination at 500 °C. Fourier-transform infrared spectroscopy, X-ray diffraction, N2 adsorption–desorption (BET and BJH), diffuse reflectance spectroscopy, particle-size distribution and scanning electron microscopy were used to characterize the materials. ZTO prepared by HPA (20 bar) showed a greater surface area. On the other hand, particles with higher mesoporosity and band gap were obtained by CO route. The US route led to the formation of ZTO with larger average particle size. Therefore, all hydrothermal routes employed in this work were able to synthesize ZTO, each one with its peculiarity, producing particles with different characteristics. The ZTO photocatalytic properties were evaluated by the decolorization of Procion red dye solution. The ZTOs synthesized by HPA and MW routes showed higher photocatalytic activity, being able to decolorize more than 70% of the dye solution at 60 min under sunlight. [ABSTRACT FROM AUTHOR]

• TiO 2 -P25 was immobilised on a fibreglass mat. • The preparation of the immobilised catalyst does not require other reagents. • The catalyst system does not require drying at high temperature. • The catalyst activity was higher than that of a TiO 2 -P25 suspension. • The catalyst system was cheap and stable (resistant to washing). The aim of this research was to produce an efficient catalytic system using a commercial photocatalyst immobilised onto a readily available support. The priority was a high catalytic activity and stability for the catalytic system as well as the simplest possible methodology for its preparation. The photocatalytic activity was verified by monitoring the decolourization of an anionic dye (Acid Orange 7) as a model molecule and antibiotics (sulfa-drugs mixture) under UVa and sunlight irradiation in distilled water and in artificial wastewater. The catalytic system stability was evaluated under cyclic and continuous processes. The developed optimised catalyst system contained one layer of TiO 2 -P25 immobilised onto a commercial glass fibre mat. This system was very simple to produce, did not require calcination prior to use and possessed a high catalytic activity, good resistance to leaching and good stability. The photocatalytic activity of the immobilised catalyst can grow asymptotically during work-up. In the cyclic process, a high activity of the catalytic system was maintained during the 11-fold use. Moreover, there was no reduction in the activity in this process at a load of 12 m3 of the Acid Orange 7 solution per 1 m2 of mat of the immobilised catalyst. The photocatalytic activity of fibreglass mat coated with TiO 2 was also confirmed during exposure to sunlight. [ABSTRACT FROM AUTHOR]

Harmful algae pollution in eutrophic waters represents one of the most serious problems in natural water environment. Adsorption assisted photocatalytic inactivation is often considered as a promising method to achieve the clean-up of harmful algae and the remediation of eutrophic water. Here, we synthesize the NP TiO 2 (nitrogen and phosphorous doped TiO 2)/C composites using a facile sol-gel method, and demonstrate successful achievement of efficient adsorption-photocatalytic performance via the in-situ formed carbides coated with NP TiO 2 nanoparticles. We find that the composites have rough surfaces with porous structure, which can be tuned by the calcination temperature, and that such composites can be served to efficiently capture the algal cells. The N and P are successfully doped into the TiO 2 crystal lattices, and the cooperation of carbides and NP TiO 2 particles enhances significantly light absorption, while inhibiting the recombination of the photogenerated charge carriers. Among all the NP TiO 2 /C composites, the NP TiO 2 /C system calcinated at 550 °C shows the best photocatalytic performance for the algal inactivation, presenting a removal rate of 92.6% following 6 h visible light irradiation. The destruction of cell structures is clearly observed in the photocatalytic process. Interestingly, the metabolic activities are also disturbed by the photogenerated radicals, which accelerates the death of algal cells. Moreover, the NP TiO 2 /C composite can effectively remove the cytotoxins from water, rendering the composite and the doping strategy promising in the remediation practice for eutrophic waters. Image 1 • NP TiO 2 /C composites were successfully prepared with a facile sol-gel method. • Higher adsorption and photocatalytic activity was obtained at 550 °C. • NP TiO 2 /C-550 achieved a high algal removal rate of 92.6% under visible light. [ABSTRACT FROM AUTHOR]

Modified TiO2 based nanomaterials have attained significant interest because of their unique morphology and excellent optical and photocatalytic properties. In this research, a very novel and highly efficient Ag2O/Fe–TiO2 porous structure was developed by simple hydrothermal method. The structural and morphological properties of the photocatalysts were studied by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The surface areas of the samples were measured by Brunauer–Emmett–Teller theory (BET). The chemical composition and optical properties were investigated using X-ray photoelectron spectroscopy (XPS) and UV–visible spectroscopy. The optical absorption measurements show a clear red-shift in absorption edge of Fe–TiO2 after loading of Ag2O (Ag2O/Fe–TiO2 composite). Moreover, Ag2O varying ratio (0–15 at.%) has also enhanced the efficiency of Ag2O/Fe–TiO2 photocatalyst for CO2 conversion into methane under visible light illumination (λ ≥ 420 nm). The optimum ratio of Ag2O loading which exhibited maximum performance is 10 at.%. Moreover, the 10%Ag2O/Fe–TiO2 composite synthesized at 180 °C hydrothermal temperature showed an excellent increase in photocatalytic activity than other composites synthesized at 150 and 210 °C. This excellent performance of photocatalyst can be attributed to the highly porous petal-like structure of composite. Therefore, it is expected that the present study will be a good addition in literature for designing highly active photocatalytic materials for reduction of CO2 into useful hydrocarbons. [ABSTRACT FROM AUTHOR]

Abstract The stability of Ag-based photocatalysts restricted their photocatalytic performance because of their photocorrosion. To solve the problem, the g-C 3 N 4 /Ag 3 PO 4 was fabricated through a calcination-deposition way and the novel g-C 3 N 4 /Ag 3 PO 4 -H 2 O 2 catalytic system was constructed in the article. The cyclic experiment and X-ray diffraction peaks of Ag 3 PO 4 and Ag 3 PO 4 -H 2 O 2 showed that the structure stability of g-C 3 N 4 /Ag 3 PO 4 -H 2 O 2 was protected by using H 2 O 2 preventing the photoetching of Ag 3 PO 4. Ultraviolet visible diffuse reflectance spectroscopy declared that the construction of g-C 3 N 4 /Ag 3 PO 4 heterojunction greatly improved the utilization of visible light. In addition, the transient photocurrent responses and photoluminescence spectra demonstrated that the photoinduced holes and electrons were separated effectively formed by g-C 3 N 4 and Ag 3 PO 4. Obviously, the above three processes promoted the excellent stability and photocatalytic performance of the g-C 3 N 4 /Ag 3 PO 4 -H 2 O 2 catalytic system. The free radical trapping experiments also proved that holes played a leading role in photocatalytic degradation, and the possible mechanism of the g-C 3 N 4 /Ag 3 PO 4 -H 2 O 2 catalytic system was proposed. Graphical abstract Image 1 Highlights • g-C 3 N 4 /Ag 3 PO 4 heterojunction was fabricated via a calcination-deposition method. • The stability of Ag 3 PO 4 was greatly improved after adding H 2 O 2. • The photogenerated charge of g-C 3 N 4 /Ag 3 PO 4 -H 2 O 2 was effectively separated. • The degradation performance of g-C 3 N 4 /Ag 3 PO 4 -H 2 O 2 was boosted by synergistic effect. • The possible routes of charge carrier transfer and separation were described. [ABSTRACT FROM AUTHOR]

In this work, a novel Z-scheme AgI/Ag/Bi24O31Cl10 photocatalyst was prepared by molecular calcination followed a precipitation–photoreduction process. AgI/Ag/Bi24O31Cl10 combines the advantages of a heterojunction with noble metal deposition. The crystalline phase, morphology, optical and photo-electrochemical properties of the prepared AgI/Ag/Bi24O31Cl10 composites have been determined. The photocatalytic activity of AgI/Ag/Bi24O31Cl10 composites was evaluated by degrading methyl orange (MO) and phenol under visible light irradiation. A mass ratio of 8% AgI in the composite was found to be optimal for the efficient degradation of MO and phenol. This was shown to degrade 84.3% of the methyl orange and 55.1% of the phenol introduced after irradiation with visible light for 2 and 4 h, respectively. Futhermore this composite is highly stable and retains excellent activity after four reaction cycles. A mechanism for the photocatalytic activity of the AgI/Ag/Bi24O31Cl10 composite has been proposed via band structure and trapping experiments. Metallic Ag0 acts as an important electron transfer intermediate between Bi24O31Cl10 and AgI. This work extends on the study of Z-scheme modifications for Bi24O31Cl10. [ABSTRACT FROM AUTHOR]

A simple sol-gel route was adopted for the preparation of TiO 2 and W6+ (0.02 at. %) doped TiO 2. The prepared samples were annealed at 500 °C (WT500) and also at 700 °C (WT700). Powder X-ray diffraction (PXRD) study confirms the anatase structure for TiO 2 and WT500 samples, whereas WT700 contains both anatase and rutile phases of TiO 2. Doping of P5+ (0.5 and 1.5 at. %) and N3− (0.2 at. %) ions into the anatase lattice structure of WT500 sample was done by wet impregnation method to get 0.5PWT500, 1.5PWT500, PWNT500, 0.5PWT900 and 1.5PWT900 catalyst samples which were annealed at 500 °C and 900 °C. P5+ dopant could effectively inhibit the phase transition of 0.5PWT900 sample from anatase to rutile, which otherwise takes place in the case of WT700 at 700 °C. Formation of titanium pyrophosphate (TiP 2 O 7) was confirmed along with anatase TiO 2 for 0.5PWT900 sample. The number of PXRD peaks pertaining to TiP 2 O 7 and their intensities increased with the increase in H 3 PO 4 concentration and the calcination temperature. X-ray photoelectron spectroscopic technique (XPS) has confirmed the oxidation states of dopant ions as W6+, P5+ and N3−. The photocatalytic activities of all the above catalysts were studied for the degradation of congo red (CR) dye as the model pollutant under UV/solar light irradiation. The tridoped PWNT500 catalyst showed higher efficiency due to the synergistic effects of dopants. An attempt is made in the present research to correlate the structure of the catalyst with the photocatalytic reactivity. Image 1 • W6+, P5+and N3− dopant ions play a crucial role in the TiO 2 crystal lattice. • Higher P5+ dopant concentration and higher annealing temperature results in TiP 2 O 7. • Various defects like V Ti ' ' ' ' V o , V o • and V o • • are formed by tridoping of TiO 2. [ABSTRACT FROM AUTHOR]

Graphical abstract C, N, F-tridoped TiO 2 nanotubes were prepared, exhibiting high photocatalytic activity for simulant wastewater under UV light and simulated sunlight. Highlights • C, N, F-tridoped TiO 2 nanotubes exhibited high photocatalytic activity. • Electronic transition was improved and band gap of TiO 2 was narrowed. • Synergy effect of the three dopants resulted in high activity. Abstract By impregnating the thermal stable TiO 2 nanotubes (C/TiO 2 NTs) in NH 4 F solution with different concentrations and subsequent calcination treatment at different temperatures, C, N, F-tridoped TiO 2 nanotubes (C, N, F/TiO 2 NTs) were prepared. XRD, XPS, TEM, TG-DTG, UV–vis and nitrogen adsorption were used to and characterize the prepared materials. The influences of dopants, calcination temperature and NH 4 F concentration on the catalytic performances of C, N, F/TiO 2 NTs under UV light and simulated sunlight were investigated by using methyl orange solution as simulant wastewater. Obtained results indicated that the C, N, F/TiO 2 NTs exhibited higher photocatalytic activity than the C-doped or N, F-codoped ones, and the C, N, F/TiO 2 NTs showed the best photocatalytic performance when they were calcinated at 300 °C and impregnated by 1 wt.% NH 4 F solution. The electronic density of states (DOS) analysis results implied that the C, N, F-tridoping could improve the electronic transition and narrow the band gap of anatase TiO 2 , and resulted in improved photocatalytic performance. The synergistic effects of the three dopants were also discussed. [ABSTRACT FROM AUTHOR]

Highlights • Mesoporous ferroelectric Bi 6 Fe 2 Ti 3 O 18 (BFTO) nanofibers were synthesized through electrospinning for the first time. • Au nanoparticles were uniformly dispersed in the porous nanofiber framework for excellent degradation efficiency. • The corona poling had greatly improved the photocatalysis performance for Au@BFTO under visible light irradiation. Abstract Mesoporous ferroelectric Bi 6 Fe 2 Ti 3 O 18 (BFTO) nanofibers with diameters of 100–150 nm are synthesized through electrospinning following by optimal calcination. The load of Au nanoparticles, as well as the corona poling, has greatly improved the photocatalysis performance, demonstrating the advantage of ferroelectricity for photocatalysis applications. [ABSTRACT FROM AUTHOR]

Highlights • Mesoporous CeO 2 nanofibers catalyst with diameter of 95 nm are successful prepared. • Calcination temperature influence the morphology and structure of CeO 2 nanofibers. • Increasing calcination temperature enhances the photocatalytic performance of CeO 2. Abstract Calcination temperature plays a critical role on morphology and structure of CeO 2 nanofibers, thus affecting its photocatalytic activity. CeO 2 nanofibers with diameter of 95 nm were successfully fabricated by electrospinning combining with calcination. The calcination temperature was determined by TGA results ranging from 500 °C to 800 °C. The morphology and structure of samples obtained with different calcination temperatures, have been characterized by SEM and XRD. Meanwhile, the specific surface area of samples were checked by BET, that was decreased 17 times from 56.3 m2/g to 3.3 m2/g, as the temperature increasing from 500 °C to 800 °C. Normally, the higher specific surface area, the more efficiency photocatalytic activity. But it was interesting that the photodegradation rate of methylene blue was increased from 67% to 98% for CeO 2 catalyst obtained at 500 °C and 800 °C, with 4 times higher kinetic constant reaction rate under UV irradiation for 60 min. It demonstrates that the photocatalytic activity of CeO 2 nanofibers catalyst is not directly related to the specific surface area, and increasing the calcination temperature has a positive effect for the photocatalytic efficiency. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • A series of BPCMSs/g-C 3 N 4 NSs was successfully prepared by a simple and cheap method. • Cr(VI) or T-Cr was completely removed or mostly recovered by BPCMSs/g-C 3 N 4 NSs. • The recycled Cr3+/BPCMSs/g-C 3 N 4 NSs showed a higher activity than BPCMSs/g-C 3 N 4 NSs. • A synergistic photocatalytic effect existed in Cr(VI)/4-FP combined pollution system. Abstract A series of biochar-coupled graphitic carbon nitride nanosheets (BPCMSs/g-C 3 N 4 NSs) composites was successfully fabricated through a simple two-step calcination strategy by using waste Camellia oleifera shells (WCOSs) and melamine as raw materials. Hexavalent chromium [Cr(VI)] or total chromium (T-Cr) in water could be completely removed or mostly recovered through adsorption combined with photocatalytic reduction by using the as-prepared BPCMSs/g-C 3 N 4 NSs. The adsorbed Cr(VI) on BPCMSs/g-C 3 N 4 NSs could be reduced by photogenerated electrons into trivalent chromium ions (Cr3+) and stably fixed on BPCMSs/g-C 3 N 4 NSs after strengthening. Interestingly, we found that the photocatalytic activity of the recycled Cr3+/BPCMSs/g-C 3 N 4 NSs was remarkably improved compared with that of the fresh BPCMSs/g-C 3 N 4 NSs for the degradation of aqueous organic pollutants. We tested the photocatalytic performance of the recycled Cr3+/BPCMSs/g-C 3 N 4 NSs in the combined pollution system containing Cr(VI) and 4-fluorophenol (4-FP) and observed that a synergistic photocatalytic effect occurred in the Cr(VI)/4-FP combined pollution system under acidic and neutral conditions. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Porous TiO 2 beads are prepared by resin templating. • The anatase/rutile bead composition can be varied through synthesis parameters. • TiO 2 beads show higher charge carrier generation and retarded charge recombination. Abstract TiO 2 in the form of macroscopic beads was prepared by resin templating. Anion-exchange macroporous resin beads were treated with a synthesis gel containing titanium isopropoxide, iso-propanol and diluted (0–5 wt.%) tetrapropylammonium hydroxide (TPAOH) aqueous solutions. The Ti-resin composite obtained was calcined at 600 °C to remove the resin. The presence of TPAOH in the precursor solution was essential for producing intact TiO 2 beads. The use of 1–1.5 wt.% TPAOH resulted in anatase beads, whereas further increase in the TPAOH content promoted the anatase to rutile phase transformations. Decreasing the heating rate used during calcination also resulted in changes in the TiO 2 composition from pure anatase (16 °C min−1 heating rate) to anatase with rutile impurities (0.5 °C min−1 heating rate). The photocatalytic activity of the TiO 2 beads was evaluated for the degradation of acetone under ultraviolet irradiation. A high activity was displayed by the TiO 2 samples composed of anatase with rutile impurities, whereas the activity was lower for pure anatase samples or samples containing mainly rutile. The TiO 2 beads showed higher rates of charge carrier generation and slower charge trapping/recombination rates compared to a reference Cristal ACTiV™ PC500. In addition, the TiO 2 beads could be used in at least five consecutive catalytic cycles without any in-between cycle treatment, without significant changes in their activity. The TiO 2 beads prepared in this work are beneficial for photocatalytic applications in the gas-phase compared to powders due to easy handling, reduced pressure drop and attrition resistance. [ABSTRACT FROM AUTHOR]

Abstract An innovative and environmentally-friendly procedure has been developed for the successful preparation of Ta 2 O 5 nanoparticles (NPs). This method includes mechanical milling and a subsequent calcination step. The in-situ formation of LiCl/KCl and the partial crystallization of Ta 2 O 5 at low-temperature were observed after milling, confirming the existence of chemical reaction between TaCl 5 and LiOH/KOH reagents, and also the mechanochemical synthesis of Ta 2 O 5. By heating at 700 °C during 2 h, complete crystallization of Ta 2 O 5 was achieved. The synthesized Ta 2 O 5 NPs showed flake shape with sizes below 20 nm and S BET of 17 m2 g−1. Furthermore, the proposed method represents an alternative for the straightforward and large-scale production of crystalline Ta 2 O 5 NPs. Moreover, the as-prepared Ta 2 O 5 NPs showed high photocatalytic activity for degrading methylene blue (MB) dye. The Ta 2 O 5 NPs enhanced the degradation rate of MB attaining a degradation percentage of about ⁓ 81% within 180 min under UV–vis irradiation. Herein, trapping experiments demonstrated that holes are the main oxidative species in the MB photodegradation process. After recycling tests, the Ta 2 O 5 NPs showed high stability which demonstrates that this photocatalyst is suitable for use in wastewater treatment. Highlights • Ta 2 O 5 nanoparticles were synthesized by an innovative and green route. • The crystallization of Ta 2 O 5 was achieved at low-temperature during milling. • Ta 2 O 5 nanoparticles showed flake shapes with sizes below 20 nm. • Ta 2 O 5 enhanced the MB photodegradation efficiency achieving ⁓ 81% within 180 min. • The two-step route is an alternative for the easy and large-scale production of Ta 2 O 5. [ABSTRACT FROM AUTHOR]

Abstract An anti-symmetric dual (ASD) Z-scheme ZnIn 2 S 4 /Er3+:Y 3 Al 5 O 12 @ZnTiO 3 /CaIn 2 S 4 photocatalyst was prepared by isoelectric point and calcination methods. The photocatalytic activity is estimated via degradation of Acid Orange II as a target organic contaminant with simultaneous hydrogen evolution under simulated solar-light irradiation. The prepared ASD Z-scheme ZnIn 2 S 4 /Er3+:Y 3 Al 5 O 12 @ZnTiO 3 /CaIn 2 S 4 photocatalyst has a high photocatalytic activity, which can be assigned to the enlarged photoresponse range, increased reduction surface and enhanced separation efficiency of photo-induced carriers. Furthermore, the cyclic experiment proves that the prepared ASD Z-scheme ZnIn 2 S 4 /Er3+:Y 3 Al 5 O 12 @ZnTiO 3 /CaIn 2 S 4 photocatalyst still maintains a high photocatalytic activity within five repetitive cycles. Moreover, the mechanism on photocatalytic degradation of organic pollutants with simultaneous hydrogen evolution caused by ASD Z-scheme ZnIn 2 S 4 /Er3+:Y 3 Al 5 O 12 @ZnTiO 3 /CaIn 2 S 4 photocatalyst is proposed. It is wished that this study could provide a promising pathway for effective degradation and rapid hydrogen production. Highlights • A novel ASD Z-scheme ZnIn 2 S 4 /Er3+:Y 3 Al 5 O 12 @ZnTiO 3 /CaIn 2 S 4 composite is designed. • Er3+:Y 3 Al 5 O 12 converts low energy light into high energy light to activate ZnTiO 3. • ASD Z-scheme can perform simultaneous pollutant degradation and hydrogen evolution. • ASD Z-scheme gives two more negative potential conduction bands producing hydrogen. • ZnIn 2 S 4 /Er3+:Y 3 Al 5 O 12 @ZnTiO 3 /CaIn 2 S 4 plays a good Z-scheme charge transfer process. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • CFO/CZS photocatalysts were synthesized by a simple calcination method. • CFO/CZS photocatalysts showed enhanced photocatalytic H 2 evolution activity. • CFO/CZS photocatalysts can be easily separated by an external magnetic field. • The possible mechanism of enhanced photocatalytic activity was discussed in detail. Abstract CoFe 2 O 4 /Cd 0.9 Zn 0.1 S (CFO/CZS) p-n junction photocatalysts were prepared by a simple calcination method. In the as-prepared CFO/CZS photocatalysts, the CoFe 2 O 4 (CFO) nanoparticles were decorated on the surface of Cd 0.9 Zn 0.1 S (CZS) nanorods. The ferromagnetic property of the as-prepared CFO/CZS photocatalysts ensures their convenient recycling by an external magnetic field. CFO/CZS photocatalysts with the mass ratio of CFO to CZS of 7% showed the highest photocatalytic H 2 evolution activity, the rate of 350.2 μmol/h, which is around 10 times higher than that of pure CZS with an apparent quantum efficiency of 27% at 420 nm. This remarkable enhancement of photocatalytic activity could be attributed to the highly efficient separation of photogenerated charge after the formation of p-n junctions. Moreover, as-synthesized CFO/CZS p-n junction photocatalysts showed strong magnetic recyclability and excellent photostability. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Ball milling followed by calcination is an effective way to introduce oxygen vacancy. • Concentration of bulk defects increases with an increase in calcination temperature. • Bulk oxygen vacancies in the form of cluster were confirmed by Cs-corrected STEM. Abstract We prepared TiO 2 /SnO x (x = 1, 2) composite coatings through ball milling followed by calcination. The composite coatings were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), spherical aberration corrected scanning transmission microscopy (Cs-corrected STEM), X-ray photoelectron spectroscopy (XPS), electron paramagnetic resonance (EPR) and other techniques. Bulk oxygen vacancies in the form of vacancy clusters rather than individual sites were directly observed by Cs-corrected STEM. With an increase in the calcination temperature from 873 K to 1073 K or holding time from five hours to ten hours, the concentration of bulk defects also increased. On the other hand, the photocatalytic activity of the as-prepared samples for degrading MB dye increased with the concentration increase of bulk defects. Sample 973 K-10 h showed the best photocatalytic activity whether under the irradiation of UV light or visible light. With a further increase in the concentration of bulk oxygen vacancies, the photocatalytic activity decreased, although surface Ti3+ defects appeared. In other words, a moderate concentration of bulk defects could benefit the enhancement of the photocatalytic activity of the as-prepared samples. Ball milling followed by calcination is an effective method to introduce defects such as oxygen vacancies. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • The Mn-Ag 3 PO 4 was successfully synthesized using the co-precipitation and calcination. • Mn incorporation decreases the broad absorption and increases the atomic ratio of O/Ag. • Mn doping reduces the large defect on the surface of Ag 3 PO 4. • The enhanced activity of Mn-Ag 3 PO 4 was due to suppressing the defect sites in the surface. Abstract The highly active Mn-doped Ag 3 PO 4 photocatalyst was successfully synthesized under coprecipitation method using AgNO 3 , Na 2 HPO 4 ·12H 2 O, and MnSO 4 ·H 2 O, followed by annealing. The products were characterized using the SEM, XRD, DRS, XPS, and BET. The results showed that the Mn doping decreased the broad absorption in the visible region and increased the atomic ratio of O/Ag. The hydroxyl defects and oxygen vacancies can be suppressed by Mn doping and the photocatalytic activity under visible light irradiation could be improved. This excellent photocatalytic activity was caused by decreasing the recombination of electron and holes due to suppressing the defect sites in the surface of Ag 3 PO 4. [ABSTRACT FROM AUTHOR]

Abstract α-Fe 2 O 3 nanoparticles with different sizes were successfully synthesized by a simple SDS-assisted grinding reaction and subsequent heating treatment process. Effects of calcination temperatures on crystal structure, optical and photocatalytic properties of the products were investigated by TG-DSC, FTIR, XRD, TEM, HRTEM, and UV–Vis techniques. Results showed that growth of the α-Fe 2 O 3 nanoparticles was very slow, and the average crystallite size gradually increased with increasing calcination temperatures. Optical measure and calculation showed that there is an increasing trend for the band gap with increase of calcination temperature. The α-Fe 2 O 3 nanoparticles obtained at 500 °C revealed higher photocatalytic degradation efficiency for MB than the other samples, attributing to the optimal value between transiting electrons and recombination of electron-hole pairs. Radical scavengers experiments implied that ·OH and e− played important roles in the photocatalytic process. The photodegradation time was greatly shortened, and the photocatalytic efficiency was further enhanced and raised to over 90% after adding H 2 O 2 , which is due to generation of a large number of the highly oxidative ·OH by photo-Fenton reaction. Highlights • α-Fe 2 O 3 nanoparticles were successfully synthesized by decomposing precursor. • Precursor was obtained by a simple SDS-assisted grinding reaction. • High photocatalytic efficiency of 99.6% was obtained for α-Fe 2 O 3 within 40 min. • It is due to generation of a large number of the ·OH by Photo-Fenton reaction. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Porous lamellar g-C 3 N 4 is synthesized by calcining the supramolecular aggregates. • The synthesized lamellar g-C 3 N 4 exhibit superior photocatalytic activity. • The enhancement in photocatalytic activity stems from the unique lamellar structure. • The work provides a facile approach to design materials with unique structure. Abstract The development of highly active photocatalysts is the primary goal in the field of photocatalysis. We herein first develop a facile and scale up approach to synthesize porous polymeric graphitic carbon nitride (g-C 3 N 4) with lamellar structure through thermal polycondensation of supramolecular aggregates. The feature of this approach lies in the directed in-situ self-assembly of cyanuric acid molecules, converted from the hydrolysis of melamine in NaOH solution, with the residual melamine molecules to form supramolecular aggregates, which lead to the formation of porous g-C 3 N 4 with lamellar structure. The synthesized lamellar g-C 3 N 4 exhibit superior photocatalytic activity as demonstrated by the complete degradation of methylene blue (MB) under one hour's visible light irradiation, as well as excellent stability with high activity retained after four runs of MB degradation testing. The enhancement in photocatalytic performance can be attributed to its unique lamellar structure with high surface area, narrow bandgap, and efficient separation of photogenerated electron-hole pairs. This work shows that the alkaline solutions can be used as the molecular self-assembly medium and opens a new avenue towards designing highly active g-C 3 N 4 -based photocatalyts for energy and environmental applications. [ABSTRACT FROM AUTHOR]

Graphical abstract Surface decorations of (001)-facet exposed TiO 2 microcrystals improve significantly the photocatalytic activity towards phenol degradations under UV light illumination. Highlights • Few-layer TiO 2 nanobelts were precipitated on TiO 2 microcrystals via a solution approach. • Both nanobelts and microcrystals were anatase TiO 2. • The belt-on-core hierarchical structure possessed enhanced photocatalytic performance. • A synergistic effect between TiO 2 microcrystals and nanobelts is anticipated. Abstract TiO 2 microcrystals exposing {001} facets are of potential applications in photocatalysis; however, the photocatalytic activity is limited by micrometer sizes. Herein, we report a compositing tactic to compensate the photocatalytic activity through surface decorations with few-layer TiO 2 nanobelts. Hydrothermally synthesized anatase TiO 2 microcrystals exposing (001) facets were immersed in a precursor solution at 60 °C, on which hydrogen titanate nanobelts precipitated vertically on the surface. A subsequent calcination in air at 400 °C was followed to decompose titanate nanobelts to anatase TiO 2 with the nanostructure maintained. The coverage of TiO 2 nanobelts can be controlled by varying the immersing duration. When utilized to assist photodegradation of phenol in water under UV light illumination, the composited TiO 2 exhibited a reaction rate constant 2.3 times that of the pristine TiO 2 microcrystals. A synergetic effect arising from the microcrystals and surface decorated nanobelts is believed to contribute to the enhanced photocatalytic activity. [ABSTRACT FROM AUTHOR]

Abstract Herein, a novel hierarchical TiO 2 pinecone-like structure (TPS) has been successfully fabricated for the first time by self-assembling anodic oxidation methods on the Ti plate. Then it was constructed that a series of CdS-TPS nanocomposites with different cycles CdS modifying by a successive ionic layer adsorption and reaction (SILAR) after different temperature annealing in air. The structures and properties of the CdS-TPS were investigated by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Current-voltage (I-V), ultraviolet-visible (UV–vis/DRS). The results shown that the optical properties of the CdS-TPS could be rationally tailored by adjusting the CdS-modified cycles and annealing temperature, which significantly enhanced photocatalytic activity. To be used in photocatalytic organic pollutant removal after optimizing both the CdS modification cycles and annealing temperature. The 15-CdS-TPS-500 °C exhibited significantly improved photocatalytic activities of methyl orange (MO) degradation under simulated sunlight irradiation. With 180 min, 85% of the MO (0.05 mM/L, 5 mL) was photodegraded and its kinetic constant reached to 0.0104 min−1, which is the 3.0 times and 3.6 times quicker than that of 5-CdS-TPS-500 °C and 15-CdS-TPS-0 °C, respectively. This could be ascribed to the result of the synergy effects of the suitable quantity of CdS nanoparticles modifier, the special surface structure, excellent crystallinity, higher electrical conductivity, and band structure matching. The possible photocatalytic mechanism of the CdS-TPS sample is investigated as well. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • The method for preparing the efficient g-C 3 N 4 /Bi 5 O 7 I photocatalyst is simple. • Microspheres with unique composition and structure can improve its performance. • The g-C 3 N 4 /Bi 5 O 7 I has the characteristic of Z-scheme type photocatalyst. Abstract Novel g-C 3 N 4 /Bi 5 O 7 I heterojunction microspheres having excellent photocatalytic activity were successfully prepared by a one-pot ethylene glycol (EG)-assisted hydrothermal method followed by calcination in air. Bi 5 O 7 I microspheres grafted with g-C 3 N 4 nano-sheets were formed and studied by electron microscopy. The morphological effects on g-C 3 N 4 /Bi 5 O 7 I photocatalytic capability with varied g-C 3 N 4 contents were investigated and discussed. The g-C 3 N 4 /Bi 5 O 7 I microspheres exhibited much improved photocatalytic degradation performance under visible light irradiation compared with bare Bi 5 O 7 I and g-C 3 N 4. The preparation conditions of g-C 3 N 4 /Bi 5 O 7 I microspheres with optimal photocatalytic ability for degrading methyl orange (MO) and rhodamine (RhB) were established. Analyses by both photoluminescence (PL) and photocurrent independently confirmed that photo-induced electron-hole pairs in the g-C 3 N 4 /Bi 5 O 7 I composite have been effectively created which was responsible for the observed photocatalysis. Based on the analysis of the experiment results, a Z-Scheme heterojunction photocatalytic mechanism was proposed. The excellent photocatalytic performance could be attributed to the effective charge separation at the interface between g-C 3 N 4 and Bi 5 O 7 I and the enhanced visible light absorption. In addition, the photocatalytic mechanism was discussed on the basis of the relative band positions of these two semiconductor materials. [ABSTRACT FROM AUTHOR]

Abstract The TiO 2 -WO 3 heterostructures with superior interfacial interactions were synthesized by simple solvothermal method followed by calcination. The electrical property of the heterostructures was tuned by varying the amount of TiO 2 and WO 3 to achieve higher photoelectrochemical activity. The prepared samples were characterized by X-ray diffraction, Raman spectroscopy, X-ray photoelectron spectroscopy, transmission electron microscopy, scanning transmission electron microscopy and UV–vis diffuse reflectance spectroscopy. The strong interaction in the interface of TiO 2 -WO 3 heterostructures and the solar spectral response of TiO 2 and WO 3 reduce the electron-hole pair recombination rate and enhance the photoelectrochemical activity. The TiO 2 -WO 3 heterostructures show 17 times higher photon-to-hydrogen conversion efficiency than pure TiO 2 and WO 3 under solar light and almost complete removal of organic pollutant in 60 min under visible light. The TiO 2 -WO 3 heterostructures also show good adsorption capacity for organic pollutants. The present study demonstrates that the prepared TiO 2 -WO 3 heterostructures are promising materials for efficient water splitting as well as adsorption and photocatalytic removal of organic pollutants. Graphical abstract fx1 Highlights • TiO 2 -WO 3 heterostructures with superior interfacial interactions were synthesized. • Enhanced photocatalytic activity of TiO 2 -WO 3 heterostructures was demonstrated. • Electrical properties were tuned by varying the amount of TiO 2 and WO 3. [ABSTRACT FROM AUTHOR]

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Here, the effect of three different ionic liquids (IL) on the structural properties and photocatalytic activity of Bismuth Vanadate (BiVO 4) was investigated. In this regard, BiVO 4 hydrothermally synthesized in the presence of three different ionic liquids, including 2-hydroxyethyl ammonium formate, 1-Ethyl-3-methylimidazolium ethyl sulfate [Emim][EtSO 4 ], and 1-Butyl-3-methylimidazolium methanesulfonate, [C 4 mim][MeSO 3 ]. Additionally, the effect of calcination temperature was also studied by calcining hydrothermally synthesized BiVO 4 at 600 °C, and all results were compared to a pure sample containing no IL. According to the characterization results, monoclinic scheelite-phase BiVO 4 was only obtained in the presence of [Emim][EtSO 4 ] and a higher temperature of 600 °C. To improve photocatalytic activity, the hybrid structure of IL-assisted BiVO 4 with MIL-100 (Fe) was constructed by the in-situ growing of MIL-100(Fe) on the surface of BiVO4 and employed as a photocatalyst for the degradation of Basic Red 46. The IL-BiVO 4 -MIL-100(Fe) hybrid material exhibited higher photocatalytic activity than bare BiVO 4 , degrading more than 88% of Basic Red 46 in 120 min. To identify the photodegradation compounds and to determine the environmental fate of Basic Red 46, gas chromatography-mass spectrometry (GC–MS) was employed, and the possible degradation mechanism was discussed and proposed. [Display omitted] • Engineering desirable properties of BiVO4 using ionic liquids as co-solvents. • Low-temperature IL-assisted synthesis of monoclinic BiVO4 photocatalyst. • Unveiling the synergistic impact of ILs and MOF on photocatalytic performance. • Determining reaction pathways and byproducts in Basic Red 46 photodegradation. [ABSTRACT FROM AUTHOR]