Commercial TiO2 Photocatalyst Research Articles

Investigation of the influencing factors and optimization study for the removal of levofloxacin in water using commercial TiO2 photocatalyst under UV-LED irradiation

Abstract Photocatalysis holds significant promise for effectively eliminating toxins, hard-to-biodegrade, and persistent organic pollutants in water. In this study, we used commercial TiO2 as a photocatalyst under UVA-LED irradiation to remove levofloxacin from water. In the photocatalytic tests, levofloxacin removal efficiency in water reached 68.21% after 120 minutes at pH 4 with an antibiotic/catalyst concentration ratio of 1:20. ANOVA revealed that the model achieved significance, as indicated by a p-value of 0.009. LEVO degradation under UVA-LED is three times higher than that under natural light. Optimal conditions for LEVO removal include pH 4, LEVO/TiO2 ratio of 1:20, and UVA-LED irradiation. The regression model predicts LEVO removal with high accuracy (R2 = 0.8469). This study highlights the use of photocatalysis with TiO2 as a promising approach for pharmaceutical pollutant removal, emphasizing the need for further research in sustainable water treatment technologies.

Augmentation of photocatalytic degradation of methylene blue dye using lanthanum and iodine Co-doped TiO2 nanoparticles, their regeneration and reuse; and preliminary phytotoxicity studies for potential use of treated water

The photocatalytic degradation of methylene blue (MB) dye using Lanthanum (La) and Iodine (I) co-doped TiO2 (Ti1−x-yLaxIyO2, where x = 0.00 – 0.05, y = 0.00 – 0.005) nanoparticles prepared through the solution combustion method has been investigated in the current study. The photocatalysts' characterization was done using various techniques, including FTIR for identifying functional groups, XRD for determining crystallinity and crystallite size, DRS for estimating the band gap, and XPS for identifying elements and their oxidation states. The co-doping of La and I in TiO2 causes narrowing the band gap and suppresses the recombination of e–/h+ pairs, which surges its photocatalytic activity. The La and I co-doped TiO2 nanoparticles exhibited a photodegradation efficiency of 98% for MB within 40 min, significantly outperforming undoped TiO2 and commercial TiO2 photocatalyst Aeroxide P-25. Moreover, regeneration experiments demonstrated excellent reusability of the nanoparticles. To find potential use of photocatalytically treated water in irrigation, the phytotoxicity study was done with "Vigna radiata" germination. The evaluation of phytotoxicity demonstrates that the treated water may be used for irrigation purposes.

Reduction of COD concentration and complete removal of phenol in industrial wastewater utilizing mesoporous TiO2 nanoparticles under UVA illumination

Toxic organic pollutants with low biodegradability are observed and detected in industrial wastewater with high contents. Phenol is one of the toxic organic compounds, and discharging it into the water can be extremely harmful to the environment and the organism's health. In this contribution, the photodegradation of phenol and minimizing COD concentration in industrial wastewater collected from the pharmaceutical industry utilizing mesoporous TiO2 nanoparticles (NPs) contrasted with commercial TiO2 photocatalysts have been conducted under UVA illumination. The results indicated that 100% phenol removal and 60.4% of the total COD were achieved at pH = 6, 1 g/L of catalyst loading, and 10.5 mg/L phenol content, 2476 mg/L of COD content within 140 min of UVA illumination. The phenol photodegradation and COD removal over the mesoporous TiO2, UV-100, and P-25 obeyed a pseudo-first-order model, and their rate constants (k) were determined about 0.0175, 0.0091 and 0.0127 min−1. The k value of mesoporous TiO2 NPs was enhanced 2 and 1.4 folds greater than that of the photocatalysts of UV-100 and P-25. The photodegradation of phenol using mesoporous TiO2 NPs for being recycled five times without losing was acquired, which indicated the obtained mesoporous TiO2 NPs are very stable for long illumination time. The active species' role during photocatalytic degradation phenol and COD removal over mesoporous TiO2 photocatalyst under illumination are the critical oxidative species of •OH and O2•− radicals. Consequently, the COD reduction and complete phenol removal in real industrial wastewater have been verified.

α-Fe2O3 Nanoparticles/Iron-Containing Vermiculite Composites: Structural, Textural, Optical and Photocatalytic Properties

Vermiculite two-dimensional mixed-layer interstratified structures are a very attractive material for catalysis and photocatalysis. The iron-containing vermiculite from the Palabora region (South Africa) and its samples, which calcined at 500 and 700 °C, were studied in comparison with the α-Fe2O3 nanoparticles/vermiculite composites for the first time as photocatalysts of methanol decomposition, which is an organic pollutant and an efficient source for hydrogen production. The aim of the work was to characterize their structural properties using X-ray fluorescence, X-ray diffraction, infrared spectroscopy, nitrogen physisorption, diffuse reflectance UV-Vis spectroscopy and photoluminescence spectroscopy to explain the photocatalytic effects. The photocatalytic test of the samples was performed in a batch photoreactor under UV radiation of an 8W Hg lamp. The photocatalytic activity of vermiculite–hydrobiotite–mica-like layers at different water hydration states in the interstratified structure and the substitution ratio of Fe(III)/Al in tetrahedra can initiate electrons and h+ holes on the surface that attack the methanol in redox processes. The activity of α-Fe2O3 nanoparticle photocatalysts stems from a larger crystallite size and surface area. The hydrogen production from the methanol–water mixture in the presence of vermiculites and α-Fe2O3 nanoparticles/vermiculite composites was very similar and higher than the yield produced by the commercial TiO2 photocatalyst Evonik P25 (H2 = 1052 µmol/gcat.). The highest yield of hydrogen was obtained in the presence of the Fe/V–700 composite (1303 µmol/gcat after 4 h of irradiation).

Titania coated silica core-shell spheres with dual grain size as efficient photocatalysts

The TiO2 nanoclusters were modified into the pores of silica core-shell particles (SiO2@dSiO2) by the sol-gel method, and the loading amount reached 47%. Based on the Ostwald ripening theory, by simply extending the reaction time, a part of the TiO2 in the pores of the shell was dissolved and then re-deposited on the outer surface of the shell to form a TiO2 layer. Using this method, TiO2 crystalline grains of different sizes were obtained simultaneously inside and outside the shell of silica core-shell spheres. Small-sized crystalline grains were located in the pores of the shell, and they had a strong quantum size effect. The large crystalline grains were located in the TiO2 layer on the outer surface of the shell of SiO2@dSiO2. Due to the formation of larger-sized crystalline grains, the recombination probability of photogenerated electron-hole pairs was reduced. When used as photocatalysts for the degradation of Rhodamine B under UV irradiation, the catalytic activity of SiO2@dSiO2@TiO2 was 5.4 times higher than that of the commercial P25 TiO2 photocatalyst.

High-loading single-atom Pt/TiO2 mesoporous catalysts for superior photocatalytic oxidation of benzyl alcohol

Photocatalysis utilized solar energy with metal oxide semiconductors has been considered as one of the attractive green routes for organics’ conversion. The construction of high-density co-catalytic sites is essential for the surface reaction kinetics. In this work, a high-efficiency mesoporous TiO2 decorated with single atomic Pt loading of 1 at% (2.1 wt%) had been successfully achieved. The high specific surface area of mesoporous TiO2 affords adequate physical surface for the resident of atomic Pt, thus stabilizing a high areal density of single-atom reaction sites. The optimized single-atom Pt/TiO2 revealed a performance of 4.1 mmol/h/gcat for photocatalytic oxidation of benzyl alcohol under visible light irradiation that is 3.8 folds than that of Pt-modified commercial TiO2 photocatalysts. The reactivity will further enhance after the introduction of plasmonic Au nanoparticles and the finally sample (1 at% Pt-0.075 at% Au)/TiO2-MP exhibited salient activity (4.5 mmol/h/gcat) and stability. This work paves a potential way to boost the performance of metal oxide semiconductors for green photocatalytic conversion of organics.

Kinetics and Mechanism of Aniline and Chloroanilines Degradation Photocatalyzed by Halloysite-TiO2 and Halloysite-Fe2O3 Nanocomposites

The kinetics of photocatalytic degradation of aniline, 2-chloroaniline, and 2,6-dichloroaniline in the presence of halloysite-TiO2 and halloysite-Fe2O3 nanocomposites, halloysite containing naturally dispersed TiO2, Fe2O3, commercial TiO2, P25, and α-Fe2O3 photocatalysts, were investigated with two approaches: the Langmuir–Hinshelwood and first-order equations. Adsorption equilibrium constants and adsorption enthalpies, photodegradation rate constants, and activation energies for photocatalytic degradation were calculated for all studied amines photodegradation. The photodegradation mechanism was proposed according to organic intermediates identified by mass spectrometry and electrophoresis methods. Based on experimental results, it can be concluded that after 300 min of irradiation, aniline, 2-chloro-, and 2,6-dichloroaniline were completely degraded in the presence of used photocatalysts. Research results allowed us to conclude that higher adsorption capacity and immobilization of TiO2 and Fe2O3 on the halloysite surface in the case of halloysite-TiO2 and halloysite-Fe2O3 nanocomposites significantly increases photocatalytic activity of these materials in comparison to the commercial photocatalyst: TiO2, Fe2O3, and P25.

Crystalline ZnO Photocatalysts Prepared at Ambient Temperature: Influence of Morphology on p-Nitrophenol Degradation in Water

Since the Industrial Revolution, technological advances have generated enormous emissions of various pollutants affecting all ecosystems. The detection and degradation of pollutants has therefore become a critical issue. More than 59 different remediation technologies have already been developed, such as biological remediation, and physicochemical and electrochemical methods. Among these techniques, advanced oxidation processes (AOPs) have been popularized in the treatment of wastewater. The use of ZnO as a photocatalyst for water remediation has been developing fast in recent years. In this work, the goals are to produce ZnO photocatalysts with different morphologies, by using a green sol-gel process, and to study both the influence of the synthesis parameters on the resulting morphology, and the influence of these different morphologies on the photocatalytic activity, for the degradation of an organic pollutant in water. Multiple morphologies were produced (nanotubes, nanorods, nanospheres), with the same crystalline phase (wurtzite). The most important parameter controlling the shape and size was found to be pH. The photoactivity study on a model of pollutant degradation shows that the resulting activity is mainly governed by the specific surface area of the material. A comparison with a commercial TiO2 photocatalyst (Evonik P25) showed that the best ZnO produced with this green process can reach similar photoactivity without a calcination step.

Experimental and modelling studies on the photocatalytic generation of hydrogen during water-splitting over a commercial TiO2 photocatalyst P25

Hydrogen, generally perceived as an environmentally friendly fuel, possesses the potential to lower society's dependency on fossil energy sources whose utilization leads inherently to global warming problems. Its photocatalytic generation from aqueous solutions is a promising green technology competitive to traditionally employed methods such as steam reforming or water electrolysis. However, the limiting yet achievable efficiencies of this process remain unclear. To address the question of process efficiencies, we formulate a phenomenological model predicting the behavior of an experimental photocatalytic reactor. The model considers the polynomial light intensity distribution, the concentration of photocatalysts, and the finite rate of the mass transfer between liquid and gas phases. We validate the model against experimental data obtained from a study with a commercially available TiO2 P25 photocatalyst used as a gold standard in photocatalysis. The theoretical analysis shows that the mass transfer of hydrogen from the liquid to gas phase significantly affects the photoreactor dynamics. Initial accumulation of hydrogen in the liquid phase and its delayed transport to the gas phase result in a nonlinear time-dependence of the hydrogen concentration in the gas phase. The theoretical average reaction rate reaches a maximum for a photocatalyst concentration of 0.23 g/L, which is in good agreement with an experimentally obtained value of 0.25 g/L. The photonic efficiency, defined as a ratio of the average reaction rate to the average light intensity, also reaches a maximum at the same catalyst concentration and interestingly remains constant for any higher TiO2 loads. Finding the optimal photocatalyst concentration and identifying the critical role of mass transfer shall aid further research in developing and optimizing photocatalytic reactors for hydrogen production in the future.

KIT-6 induced mesostructured TiO2 for photocatalytic degradation of methyl blue.

In this study, titania/silica nanocomposite and mesoporous TiO2 (m-TiO2) photocatalysts are developed by KIT-6 template via a sol-gel approach. The synthesized photocatalysts are characterized by XRD, EDX, SEM, Raman, PL, and UV-vis DRS analysis techniques. The as-synthesized series revealed a high surface area, smaller size, a greater number of accessible active sites, and enhanced light-harvesting capability. The m-TiO2 photocatalysts' charge recombination capability was curiously inferior to the rest of as-synthesized TiO2/KIT-6 nanocomposite materials. The band-gap of as-synthesized materials were suitable for their activity in UV light irradiations. It was pragmatic that the photocatalytic degradation efficiency of m-TiO2 photocatalysts was superior as compared to that of commercial TiO2 photocatalyst under UV light irradiations, owing to the synergistic outcome of the anatase phase and a greater number of accessible active-sites availability as a result of high surface area. Moreover, the m-TiO2 was critically evaluated by investigating various parameters affecting the photocatalytic degradation reaction of MB including the effect of irradiation time, pH, catalyst dosage, and dye concentration. The m-TiO2, 45wt% composite material and commercial-TiO2 exhibited 99.27, 91.20, and 84.67% degradation of methyl blue in 50 min, respectively. Finally, the m-TiO2 exhibited excellent recyclability with negligible loss of activity performance.

Synergism in TiO2 photocatalytic ozonation for the removal of dichloroacetic acid and thiacloprid

The synergistic effect of the photocatalytic ozonation process (PH-OZ) using the photocatalyst TiO2 is usually attributed to influences of the physicochemical properties of the catalyst, pollutant type, pH, temperature, O3 concentration, and other factors. It is also often claimed that good adsorption on the TiO2 surface is beneficial for the occurrence of synergism. Herein, we tested these assumptions by using five different commercial TiO2 photocatalysts (P25, PC500, PC100, PC10 and JRC-TiO-6) in three advanced oxidation systems - photocatalysis (O2/TiO2/UV), catalytic ozonation (O3/TiO2) and PH-OZ (O3/TiO2/UV) - for the degradation of two pollutants (dichloroacetic acid - DCAA and thiacloprid) simultaneously present in water. The synergistic effect in PH-OZ was much more pronounced in the case of thiacloprid, a molecule with low adsorption on the surface of the catalyst - in contrast to DCAA with stronger adsorption. The faster kinetics of catalytic ozonation (O3/TiO2) correlated with the higher exposed surface area of TiO2 agglomerates, independent of the (lower) BET surfaces of the primary particles. Nevertheless, DCAA mineralization on the TiO2 surface was much faster than thiacloprid degradation in solution. Therefore, we propose that a high BET surface area of the photocatalyst is crucial for fast surface reactions (DCAA mineralization), while good dispersion - the high exposed surface area of the (small) agglomerates - and charge separation play an important role in photocatalytic degradation or PH-OZ of less adsorbed organic pollutants (thiacloprid).

Tuning the selectivity to aldehyde via pH regulation in the photocatalytic oxidation of 4-methoxybenzyl alcohol and vanillyl alcohol by TiO2 catalysts

The influence of pH on the photocatalytic partial oxidation of 4-methoxybenzyl alcohol (MBA) and vanillyl alcohol (VA) to their corresponding aldehydes in aqueous suspension under UVA irradiation was investigated by using poorly crystalline home-prepared and crystalline commercial TiO2 (BDH, Merck and Degussa P25) photocatalysts. The results clearly show as tuning pH can strongly impart selectivity and activity to photocatalytic processes which are often quite unselective in aqueous suspensions. It was found that pH effect on reaction rate and product selectivity strongly depended on TiO2 crystallinity and substrate type. In the case of MBA oxidation, photoreactivity and selectivity were very high at low pH values for all of TiO2 catalysts, and the crystalline samples showed to be more active than the poorly crystalline ones. At pH= 1 the photoactivity of Degussa P25 was the highest one, and 88% selectivity at 50% conversion was determined. At acidic pH values, selectivity and activity were higher in the presence of HCl than H2SO4 or H3PO4. For VA oxidation, high selectivity values were obtained at high pH’s for all of the samples, and the crystalline samples showed higher activity at the alkaline pH values with respect to that observed at the acidic ones. Experiments starting from the obtained products, that are p-anisaldehyde and vanillin, showed that the selectivity depends on the resistance of those compounds to be subjected to further oxidation under the experimental conditions used.

In-situ synthesis of Z-Scheme MIL-100(Fe)/α-Fe2O3 heterojunction for enhanced adsorption and Visible-light photocatalytic oxidation of O-xylene

Abstract Though exhibiting excellent performance in the adsorption of organic gas pollutants, the application of MOFs is still limited in the photocatalytic oxidation (PCO) of volatile organic compounds (VOCs) due to the short lifetime of photogenerated electron-hole pairs. MIL-100(Fe)/α-Fe2O3 photocatalysts were fabricated through a facile one-step hydrothermal method by adjusting the coordination of Fe(III) ions for the PCO of typical VOCs. The large specific surface area (763 m2 g−1), uniformly distributed active sites and suitable pore structure of the composites enable the effective adsorption of target o-xylene molecules. The MIL-100(Fe)/α-Fe2O3 hybrid presented a high o-xylene removal efficiency of 100% under 250 W xenon (Xe) lamp irradiation and 90% under visible light (λ ≥ 420 nm), which is far beyond the performance of commercial TiO2 photocatalyst under the same conditions (23% under 250 W Xe lamp irradiation and 0% under visible light). The ESR results confirmed the formation of Z-scheme structure and revealed that the reversible conversion of Fe(III) and Fe(II) under light irradiation plays a key role in the oxidation of o-xylene and the effective generation of reactive radicals. The PCO mechanism of o-xylene was analyzed through in-situ DRIFTS. This work not only provides a means for the synthesis and optimization of high performance photocatalysts based on MOFs for air purification, but also shed light on the PCO mechanism of o-xylene by MOFs photocatalysts.

Photocatalytic H2 Production from Naphthalene by Various TiO2 Photocatalysts: Impact of Pt Loading and Formation of Intermediates

This work presents a comparative study of the efficiency of two commercial TiO2 photocatalysts, Aeroxide P25 (ATiO2) and Sachtleben Hombikat UV100 (HTiO2), in H2 production from an aqueous solution of naphthalene. The TiO2 photocatalysts were platinized by the photodeposition method varying the platinum content of the suspension to 0.5, 1.0, and 5.0 wt%. A full physicochemical characterization for these materials was performed, showing no structural effects from the deposition method, and confirming a well dispersion of nanosized-Pt0 particles on the surface of both photocatalysts. Pristine ATiO2 shows around 14% higher photocatalytic fractional conversion of naphthalene than pristine HTiO2 after 240 min of irradiation, while both materials exhibit negligible activity for H2 formation. The 0.5 wt% Pt- HTiO2 increases the photocatalytic fractional conversion of naphthalene from 71% to 82% and produces 6 µmol of H2. However, using a higher Pt content than the optimal platinization ratio of 0.5 wt% dramatically inhibits both processes. On the other hand, regardless of the fractional ratio of Pt, the platinization of ATiO2 results in a decrease in the fractional conversion of naphthalene by 4% to 33% of the pristine value. Although the presence of Pt islands on the surface of the ATiO2 is essential for the H2 evolution, no dependency between the Pt ratio and the H2 formation rate was observed since all the platinized materials show a similar H2 formation of around 3 µmol. Based on the EPR results, the higher photocatalytic activity of the Pt-HTiO2 is attributed to the efficient charge carrier separation and its larger surface area. The recyclability test confirms that the inhibition of the photocatalytic process is related to the deactivation of the photocatalyst surface by the adsorption of the photoformed intermediates. A strong relationship between the photocatalytic activity and the kind of the aromatic compounds was observed. The H2 evolution and the photooxidation of the aromatic hydrocarbons exhibit higher photonic efficiencies than that of their corresponding hydroxylated compounds over the Pt-HTiO2.

Hierarchical Bi2O2CO3 wrapped with modified graphene oxide for adsorption-enhanced photocatalytic inactivation of antibiotic resistant bacteria and resistance genes

There is growing pressure for wastewater treatment plants to mitigate the discharge of antibiotic resistant bacteria (ARB) and extracellular resistance genes (eARGs), which requires technological innovation. Here, hierarchical Bi2O2CO3 microspheres were wrapped with nitrogen-doped, reduced graphene oxide (NRGO) for enhanced inactivation of multidrug-resistant E. coli NDM-1 and degradation of the plasmid-encoded ARG (blaNDM-1) in secondary effluent. The NRGO shell enhanced reactive oxygen species (ROS) generation (•OH and H2O2) by about three-fold, which was ascribed to broadened light absorption region (red-shifted up to 459 nm) and decreased electron-transfer time (from 55.3 to 19.8 ns). Wrapping enhanced E. coli adsorption near photocatalytic sites to minimize ROS scavenging by background constituents, which contributed to the NRGO-wrapped microspheres significantly outperforming commercial TiO2 photocatalyst. ROS scavenger tests indicated that wrapping also changed the primary inactivation pathway, with photogenerated electron holes and surface-attached hydroxyl radicals becoming the predominant oxidizing species with wrapped microspheres, versus free ROS (e.g., •OH, H2O2 and •O2−) for bare microspheres. Formation of resistance plasmid-composited microsphere complexes, primary due to the π-π stacking and hydrogen bonding between the shell and nucleotides, also minimized ROS scavenging and kept free plasmid concentrations below 102 copies/mL. As proof-of-concept, this work offers promising insight into the utilization of NRGO-wrapped microspheres for mitigating antibiotic resistance propagation in the environment.

Synthesis and Visible-Light Photocatalytic Activity of Graphite-like Carbon Nitride Nanopowders

Graphite-like carbon nitride (g-C3N4) nanopowders were synthesized by heat treatment of urea in air at a temperature of 450–550°С for 30 min and studied by X-ray diffraction and infrared spectroscopy. The main processes resulting in the formation of g-C3N4 from urea under the above conditions was established using the method of simultaneous thermal analysis. It was found that with an increase in the processing temperature of urea from 450 to 550°C, a rise in the specific surface of the powders occurs from 43.3 to 58.6 m2 g–1, as well as an increase in the crystallite sizes of graphite-like carbon nitride in the crystallographic direction (002) from 2.8 to 4.1 nm. According to the results of scanning electron microscopy and low-temperature nitrogen adsorption, the obtained graphite-like carbon nitride powders have a mesoporous structure and are characterized by an average pore size of 6.6–13.8 nm and porosity of 0.07–0.20 cm3 g–1. According to the results of diffuse reflectance spectroscopy, it was found that g-C3N4 nanopowders absorb radiation in the visible region and have a band gap of 2.9 eV. The photocatalytic activity of the obtained graphite-like carbon nitride during the oxidation of an aqueous murexide solution under the influence of visible light was analyzed and it was shown that the obtained g-C3N4 nanopowders have activity close to that of the commercial TiO2 photocatalyst (AEROXIDE P25). In view of the high activity and low cost, the obtained powders of graphite-like carbon nitride can be used as the substrate for new photocatalytic materials.

Trioctylphosphine (TOP)-free synthesis of TiSe2 plates for enhanced photocatalytic degradation performance of Rhodamine B dyes

Two-dimensional (2D) photocatalysts have attracted increasing attentions in the past decades due to their unique physical and chemical properties. In this work, the photocatalytic performance of TiSe2 plates and the corresponding photocatalytic degradation mechanism for Rhodamine B (Rh B) solution were studied for the first time. The TiSe2 plates were successfully synthesized via a facile TOP-free chemical method at different growth time. The crystal phase, morphology, crystal structure, optical properties, surface processes electrons (e−) - holes (h+) pairs and electrochemical property were characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscope, UV–vis spectroscopy, photoluminescence, and electrochemical impedance spectroscopy. The photocatalytic activity of TiSe2 plates was evaluated by the degradation of Rh B under sunlight irradiation. Compared with commercial TiO2 (P25) photocatalyst, the TiSe2 photocatalysts exhibited enhanced photocatalytic degradation of Rh B. TiSe2 photocatalyst prepared at 90 min exhibited best photocatalytic activity of 96% in 30 min under sunlight irradiation. This work suggested that TiSe2 plates could be a promising photocatalyst candidate and might stimulate the further studies of TiSe2-based photocatalysts for environmental-pollution applications.

Synthesis of core/shell Ti/TiOx photocatalyst via single-mode magnetic microwave assisted direct oxidation of TiH2

Submicron core/shell Ti/TiOx photocatalyst is successfully synthesized via single-mode magnetic microwave (SMMW) assisted direct oxidation of planetary ball-milled TiH2. The thickness of TiOx shell including highly concentrated defects such as Ti3+ and/or oxygen vacancies is controllable in the range from 6 to over 18 nm by varying the treatment time in the SMMW assisted reaction. In addition to its quite narrow optical bandgap (1.34–2.69 eV) and efficient visible-light absorption capacity, the submicron Ti/TiOx particle exhibits superior photocatalytic performance towards H2 production from water under both UV and visible-light irradiation to compare with a commercial TiO2 photocatalyst (P-25). Such excellent performance can be achieved by the synergetic effect of enhancement in visible light absorption capacity and photo-excited carrier separation because of the highly concentrated surface defects and the specific Ti/TiOx core/shell structure, respectively.

Hydrophilic macroporous SnO2/rGO composite prepared by melamine template for high efficient photocatalyst

Based on the electrostatic interaction between melamine and graphene oxide (GO), and the solubility of melamine in hot water, we adopt melamine as template and prepare hydrophilic macroporous SnO2/reduced graphene oxide (SnO2/rGO-HM) composite for high efficient photocatalyst. During the preparation process, SnO2 nanoparticles are synthesized on GO sheets by hydrolysis of SnCl4·5H2O, and then melamine particles are added to form clad structure with melamine as cores and SnO2/GO as cladding layers. During subsequent heat annealing, melamine cores protect the oxygen-containing groups on the inner layer of SnO2/GO sheet, which ensures the hydrophilicity of SnO2/rGO composite. Meanwhile, melamine templates are removed by rinsing in hot water to produce macroporous structure. As a template agent, the effect of melamine dosage on the pore structure and photocatalysis performance is discussed. Moreover, the relationship between SnCl4·5H2O dosage and photocatalytic activity of SnO2/rGO-HM composite is also clarified. When used for degradation of Rhodamine B and methylene blue, SnO2/rGO-HM photocatalyst shows a better photocatalytic activity than that of ordinary SnO2/rGO, pure SnO2, and commercial TiO2 photocatalyst (P25). The excellent photodegradation performance is attributed to the hydrophilicity, high specific surface area of composite, and the uniform distribution of SnO2 nanoparticles on rGO sheets.

Alcohol solvothermal reduction for commercial P25 to harvest weak visible light and fabrication of the resulting floating photocatalytic spheres

In this study, to fabricate stable floating photocatalytic spheres, facile alcohol solvothermal reduction was first employed to modify commercial TiO2 (P25) photocatalysts to harvest visible light and improve their performances for photodegrading phenol in seawater exciting by visible light. Floating photocatalytic spheres were then prepared by loading reduced P25 photocatalysts on inner and outer surfaces of acrylic hollow spheres. The structural characterizations showed that reduction of P25 introduced disorder–crystalline shell–core structures with present Ti3+ in reduced P25 photocatalysts. These features facilitated visible light response and phenol degradation in seawater under visible light irradiation. As reduction time or temperature of alcohol solvothermal process rose, more Ti3+ and shell–core structures were introduced into reduced P25, resulting in higher performances towards phenol degradation in seawater. However, extended periods of time and elevated temperatures decreased disordered layer of reduced P25, deteriorating the photocatalytic performances. Thanks to good light transmission of the hollow spheres and the high performance of the reduced P25, the photocatalytic performances of spheres loaded with reduced P25 could effectively degrade phenol in seawater even at low concentrations. The removal rate of phenol by floating spheres reached more than 95% after 8 h. In addition, the floating spheres displayed good stability and convenient reusability after six repeated photocatalytic degradation for phenol in seawater, promising features for future treatment of organic pollutants in oceans.