Coupling TiO2 Research Articles

Enhanced Visible-Light Photocatalysis Activity of TiO2/Ag Nanocomposites Prepared by the Ultrasound-Assisted Sol–Gel Method: Characterization and Degradation–Mineralization of Cationic and Anionic Dyes

Coupling TiO2 with various elements could enhance its photocatalytic activity. In this study, an innovative ultrasound-assisted sol–gel method was used to synthesize TiO2/Ag(x%) by varying Ag–support mass (x = 9.3, 17.1, and 23.6%), followed by calcination at 450 °C for 30 min. The aim was to demonstrate that Ag compositing improves photoactivity under visible light (>400 nm). The synthesized photocatalysts were assessed for their effectiveness in the degradation and mineralization of Methylene Blue (MB) and Acid Orange 7 (AO7) using visible lamps emitting in the range of 400–800 nm. Characterization of the prepared photocatalysts was performed by using Raman spectroscopy, SEM/EDS, pHpzc, and UV–visible spectroscopy. Raman spectroscopy confirmed the predominance of the anatase phase in all the photocatalysts. The photodegradation efficiencies of the selected dyes, MB and AO7, reached 99% (pH 6) and 95% (pH 3) after 180 min of irradiation, respectively. The best performance for the degradation of the two dyes was observed with TiO2/Ag9.3%, showing optimal kinetics at this doping concentration. The improved photoactivity of the TiO2/Ag composite is due to a decrease in the recombination rate of electron/hole (e−/h+) and a decrease in the band gap from 3.13 to 2.49 eV. The mineralization rate of both dyes under visible light is about 9.3%, indicating the presence of refractory by-products that resist complete degradation. Under UVA irradiation, complete mineralization is obtained. This study confirms the potential of TiO2/Ag composite as a high-performance and cost-effective photocatalyst for solar environmental remediation, highlighting the role of silver in extending light absorption into the visible region and improving charge separation.

Synergistic adsorption–photocatalytic degradation of the emerging contaminant hydroxybenzotriazole by a 3D sponge-like easy separation polypyrrole/TiO2 composite

Herein, a 3D sponge-like polypyrrole/TiO2 (Ppy-TiO2) composite aerogel was developed for the first time to remove hydroxybenzotriazole (HOBt) from water. Mesoporous TiO2 was prepared via a sol–gel method, and then the Ppy-TiO2 composite hydrogel was prepared by oxidative polymerization and converted to aerogel by freeze-drying. The morphological, compositional, and surface characteristics of the prepared materials were detailly characterized. The characterization studies revealed that pure anatase mesoporous TiO2 nanoparticles were successfully prepared and incorporated into amorphous 3D Ppy with a porous chain-like network structure. Coupling Ppy and TiO2 extended the light absorption to the visible region and decreased the electron/hole recombination rate. The performance studies revealed that the Ppy-TiO2 composite has higher adsorption and photocatalytic activities than the sum of the individual components. Optimum performance was obtained at pH 5.3 using 0.25 g/L of the Ppy-TiO2 composite with a Ppy: TiO2 mass ratio of 1:1. The intermolecular hydrogen bonding was pivotal in the adsorption process which was multilayer. The degradation of HOBt occurs primarily by holes, then superoxide anion radicals. The total organic carbon (TOC) analysis showed a 90% reduction in carbon content after 30 min of treatment. The toxicity study indicated that the photocatalytic process decreased the toxicity of the HOBt solution. The synergism between adsorption and photocatalysis, easy separation, and reusability promote the application of Ppy-TiO2 composite aerogel for water treatment.

Three-dimension TiO2@NiFe-layered double hydroxide core-shell heterostructures for enhanced photocatalytic phenol hydroxylation

One-step selectively photocatalytic phenol hydroxylation to produce Dihydroxybenzenes (DHB) is an attractive and challenging strategy. However, the rapid recombination of photogenerated carriers existed in single component photocatalyst seriously hinders the photocatalytic efficiency. The heterojunction strategy can optimize the band structure of the photocatalyst, and effectively improve the carriers' separation and transfer during the photocatalytic process. Herein, we successfully designed and prepared a 3D TiO2@Ni3Fe1-LDH core-shell heterostructure photocatalyst by coupling TiO2 nanorods with Ni3Fe1-LDH nanosheets for the photocatalytic phenol hydroxylation to produce DHB. The results showed that the 3D TiO2@Ni3Fe1-LDH core-shell heterostructure had a suitable energy band structure for the photocatalytic phenol hydroxylation and the heterostructure accelerated the carriers’ separation and transfer. Meanwhile, the high porosity and abundant active sites were conducive to the adsorption of H2O2 and the photogenerated carriers transfer efficiency from the photocatalyst to H2O2. The 3D TiO2@Ni3Fe1-LDH core-shell heterostructure showed excellent photocatalytic performance of phenol hydroxylation, where the phenol conversion was 48.6%, and the selectivity of DHB was 81.1% at 25 °C and 4 h of light illumination. Furthermore, the as-prepared photocatalysts exhibited good stability after four cycles of experiment. This work provided a convenient and efficient method for the green synthesis of DHB.

Coupling ultrafine TiO2 within pyridinic-N enriched porous carbon towards high-rate and long-life sodium ion capacitors

Coupling TiO2 within N-doped porous carbon (NPC) is essential for enhancing its Na+ storage performance. However, the role of different N configurations in NPC in improving the electrochemical performance of TiO2 is currently unknown.In this study, melamine is deliberately incorporated as a pore-forming agent in the self-assembly process of metal organic framework precursors (NH2-MIL-125(Ti)). This intentional inclusion of melamine leads to the one-pot and in-situ formation of highly active edge-N, which is vital for the development of TiO2/NPC with exceptional reactivity. Electrochemical performance characterization and density functional theory (DFT) calculation indicate that the interaction between TiO2 and pyridinic-N enriched NPC can effectively narrow the bandgap of TiO2/NPC, thereby significantly improving electron/ion transfer. Additionally, the abundant mesoporous channels, high N content and oxygen vacancies also contribute to the fast reaction kinetics of TiO2/NPC. As a result, the optimized TiO2/NPC-M, with high proportion of pyridinic-N (44.1 %) and abundant mesoporous channels (97.8 %), delivers high specific capacity of 282.1 mA h−1 at 0.05 A g−1, superior rate capability of 177.3 mA h−1 at 10 A g−1, and prominent capacity retention of 89.3 % over 5000 cycles even under ultrahigh 10 A g−1. Furthermore, the TiO2/NPC-M//AC sodium ion capacitors (SIC) device achieves a high energy density of 136.7 Wh kg−1 at 200 W kg−1. This research not only offers fresh perspectives on the production of high-performance TiO2-based anodes, but also paves the way for customizing other active materials for energy storage and beyond.

Synthesis of CuO, ZnO and SnO2 Coupled TiO2 Photocatalyst Particles for Enhanced Photodegradation of Rhodamine B Dye

Environmental pollution is a global problem and dye pollution is one of the major factors. TiO2 shows promising photocatalytic properties that can degrade organic pollutants such as dye under ultraviolet (UV) irradiation. However, TiO2 possesses some disadvantages such as a wide band gap and a high recombination rate of electron-hole pairs. Coupling TiO2 with various metal oxides can enhance photocatalytic properties. In this work, photodepositon (reduction of metal ions on TiO2) followed by the thermal oxidation method were used for the coupling of TiO2 with CuO, ZnO, or SnO2 under various methanol concentrations (25 vol% or 50 vol%) and deposition duration (1 h or 3 h) to observe the effect of these parameters on the photocatalytic degradation activity on Rhodamine B (RhB) dye (up to 90 min). The rate constant of the photodegradation reaction (k) has improved from 0.0141 min−1 (uncoupled TiO2) to 0.0151~0.0368 min−1. Overall, CuO/TiO2 and SnO2/TiO2 samples have shown similar photocatalytic properties (average rate constants of 0.0341 min−1 and 0.0327 min-1, respectively), and both performed better than ZnO/TiO2 in terms of RhB photodegradation (average rate constants of 0.0197 min−1). The difference in photocatalytic performance can be explained by the bandgap of metal oxides and their relative band positions with TiO2. Lastly, CuO/TiO2 (50 vol%, 3 h) and SnO2/TiO2 (50 vol%, 3 h) have shown the best photocatalytic properties respectively due to a longer deposition time and higher concentration methanol, resulting in more deposited materials. Copyright © 2023 by Authors, Published by BCREC Group. This is an open access article under the CC BY-SA License (https://creativecommons.org/licenses/by-sa/4.0).

3D ordered macroporous sulfur-doped g-C3N4/TiO2 S-scheme photocatalysts for efficient H2O2 production in pure water

Photocatalytic hydrogen peroxide (H2O2) production offers a clean and cost-efficient alternative to the traditional anthraquinone oxidation approach. Herein, a step-scheme (S-scheme) heterojunction photocatalyst is fabricated by coupling TiO2 with three dimensionally ordered macroporous sulfur-doped graphitic carbon nitride (3DOM SCN/T) by electrostatic self-assembly. The optimized photocatalyst achieved a high photocatalytic H2O2 production activity with a yield of 2128 μmol h−1g−1 without the addition of hole scavengers. The remarkable performance was attributed to the synergy between the 3DOM framework and the S-scheme heterojunction. The former enhances light harvesting and provides abundant active sites for surface reactions, while the latter promotes the spatial separation of photogenerated carriers and enhances the redox power. Finally, the mechanism of photocatalytic H2O2 production over the 3DOM SCN/T S-scheme composite is proposed. This work provides novel insights into the development of efficient photocatalysts for H2O2 production from water and O2.

Experimental and theoretical photocatalytic potential of binary NiTiO2 and ternary CdNiTiO2 nanocomposites of TiO2

The large band gap and the high electron–hole pair recombination rate of neat TiO2 limit its practical applications. Among different approaches, the nanocomposite formation by coupling TiO2 with other semiconducting materials of lower gap energy is a magnificent option. The same approach was followed for synthesizing NiTiO2 and CdNiTiO2 nanocomposites by co-precipitation method. The morphological analysis of the synthesized materials performed via scanning electron microscopy shows aggregated spherical shaped TiO2 NPs, while the synthesized nanocomposites have irregular shapes found in both dispersed and aggregated forms. The components of the nanocomposites are well mixed and intercalated to each other as confirmed by transmission electron microscopy. The X-Ray diffraction and energy dispersive X-ray analyses confirmed the anatase TiO2 of high purity. Brunauer Emmett Teller analysis has shown a 50.2 m2/g surface area for the ternary CdNiTiO2 nanocomposite. A red shift in the absorbance wavelength and decrease in band gap energy of the NiTiO2 (2.5 eV) and CdNiTiO2 (2.4 eV) compared to TiO2 (2.6 eV) shows efficient photocatalytic activity for the nanocomposites. The photo-degradation experiments in aqueous media by UV light interaction revealed about 72, 77, and 91.2% methylene blue and 69, 80, and 94.5 methyl orange dyes degradation for TiO2, NiTiO2 and CdNiTiO2, respectively within 100 min. Maximum photo-degradation is achieved in the basic medium (pH 10) and with a 0.030 g of photo-catalyst dosage. The density functional theory (DFT) simulations show that both the nanocomposites are energetically favorable, stable and show significantly tuned electronic properties compared to neat TiO2.

TiO2/g-C3N4 Binary Composite as an Efficient Photocatalyst for Biodiesel Production from Jatropha Oil and Dye Degradation.

In the present work, TiO2/g-C3N4 nanocomposites were synthesized by using highly crystalline TiO2 nanorods/rice (NRs) and various percentages of g-C3N4 via a facile, scalable, and inexpensive pyrolysis method. The synthesized nanocomposites were characterized by various techniques, e.g., X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), N2 adsorption and desorption analysis (BET), Fourier transform infrared spectroscopy (FTIR), UV-vis diffuse reflectance spectroscopy (DRS), electrochemical impedance spectroscopy (EIS), and chronoamperometry (CA). It was found that biodiesel production by the esterification reaction can be remarkably enhanced by coupling TiO2 with g-C3N4; hereby, it was observed that with increasing percentage of g-C3N4 from 5 to 10 and 15% with respect to TiO2 NRs, the photocatalytic activity rose and the maximum photocatalytic activity with 97% conversion was observed for NC-3, i.e., 15% g-C3N4/TiO2. Moreover, the photoactivity of pristine TiO2 NR aggregates was contrasted with their nanoparticle morphology and was estimated to be slightly better. When applied for photocatalytic Congo red dye degradation, this sample showed a 91% degradation efficiency using only a very small amount of the catalyst. The high catalytic efficiency is attributed to the narrow band gap, exceptionally high surface area, and efficient charge separation properties of the prepared catalysts.

Visible light degradation of ibuprofen using PANI coated WO3@TiO2 photocatalyst

A PANI-coated heterojunction of WO3@TiO2 nanocomposite was fabricated in three stages. The performance evaluation of the prepared photocatalyst for the degradation of ibuprofen was performed under visible light. Characterization of the photocatalyst using X-ray diffraction (XRD) analysis showed that the TiO2 prepared constituted of the anatase phase. Furthermore, results from in situ XRD analysis of WO3 show that it consisted of monoclinic and orthorhombic crystalline structures. These phases were not affected by the incorporation of PANI as revealed by XRD analysis. Results from Transmission electron microscopy (TEM) examination showed that sphere-like WO3 and TiO2 nanorods of different sizes were prepared In addition, fabrication of a heterojunction of WO3@TiO2 wrapped in PANI was shown by TEM analysis. Results from photoluminescence studies indicate that coupling TiO2 with WO3 enhanced the charge separation and the degradation performance of the nanocomposite. Supporting the heterojunction on PANI enhanced the degradation efficiency as indicated during the performance evaluation process. Diffuse reflectance spectra (DRS) calculations of the PANI/WO3@TiO2 catalysts showed that they can be used under visible light. The experimental results of X-ray Photon Spectroscopy (XPS) analysis showed the presence of elements W, C, O, Ti, and N. Solution pH influenced the degradation process and the maximum degradation efficiency was attained at pH 9. The degradation followed the Langmuir-Hinshelwood kinetic model with a Kinetic constant of 3.5 × 10−2. The rate of degradation increased in the presence of bicarbonate/carbonate ions and persulfate ions.

Use of TiO2 in Photocatalysis for Air Purification and Wastewater Treatment: A Review

This study reviews recent research on the synthesis and application of titanium dioxide (TiO2)-based photocatalysts for environmental applications. The principles of non-homogenous photo-catalysis include utilizing a solid semiconductor, such as titanium dioxide Nano or macro, to form a stable suspension (heterogeneous phase) at the impact of irradiation to elevate a reaction at the surface interface of the different phases in the system. Recently, titanium dioxide has been considered the better semiconductor in non-homogenous photoinduced treatment. TiO2-based photocatalysts have broad applications for industrial processes because of their exceptional physicochemical properties. Nevertheless, having a narrow band near the ultraviolet region limits its applications within visible radiation. As a result of this, there have been considerable research efforts to improve the visible light tendency of TiO2 through modifications of its optical and electronic properties. Several strategies, such as coupling TiO2 tightly and incorporating other metallic components during synthesis, have increased the bandgap of TiO2 for visible light applications. Moreover, an overview of nanotechnology that could enhance the properties of TiO2-based catalysts in an environmentally friendly way to decompose pollutants is also presented. The various TiO2-based photocatalysts have wide applications in degrading recalcitrant pollutants in the air, water, and wastewater treatment under visible light.

Pyropheophorbide-a/(001) TiO2 Nanocomposites with Enhanced Charge Separation and O2 Adsorption for High-Efficiency Visible-Light Degradation of Ametryn.

It is highly desired to enhance charge separation and O2 adsorption of the pyropheophorbide-a (Ppa) to promote visible-light activity and stability. Herein, Ppa modified 001-facet-exposed TiO2 nanosheets (Ppa/001T) nanocomposites with different weight ratios were fabricated via the self-assembly approach by OH induced. Compared with the bare Ppa, the 8% amount optimized 8Ppa/001T sample displayed 41-fold enhanced activity for degradation of Ametryn (AME) under visible-light irradiation. The promoted photoactivities could be attributed to the accelerated charge carrier’s separation by coupling TiO2 as thermodynamic platform for accepting the photoelectrons with high energy from Ppa and the promoted O2 adsorption because of the residual fluoride on TiO2. As for this, a distinctive two radicals (•O2− and •OH) involved pathway of AME degradation is carried out, which is different from the radical pathway dominated by •O2− for the bare Ppa. This work is of utmost importance since it gives us detailed information regarding the charge carrier’s separation and the impact of the radical pathway that will pave a new approach toward the design of high activity visible-light driven photocatalysts.

Enhancing photoelectrochemical cathodic protection performance by facile tuning sulfur redox state in sacrificial agents

Photocathodic protection (PCP) performance is restricted by the photogenerated charges separation efficiency. This study reported a facile approach to enhance PCP performance. Na2S, Na2SO3, Na2S2O3, Na2SO4, and NaCl was selected as sacrificial agents, in which the PCP performance is characterized by coupling TiO2 and TiO2/ZnSe composites with 304 stainless steel. TiO2/ZnSe photoanode presented the best PCP performance in Na2S media. The maximum potential drop is 466.7 mV, which is about 3.5 times higher than that of in NaCl media. The corresponding photocurrent density is 270.7 μA/cm2, which is about 10 times higher than that of in NaCl media. Based on circle voltammetry and ultraviolet photo-electron spectroscopy characterization, it was found that the redox potential of the sacrificial reagent governs the migration and consumption of photogenerated holes of the photoanode.

Carbon dots incorporated in hierarchical macro/mesoporous g-C3N4/TiO2 as an all-solid-state Z-scheme heterojunction for enhancement of photocatalytic H2 evolution under visible light

In recent years, coupling TiO2 with other narrow bandgap semiconductors to improve photocatalytic hydrogen generation rate has attracted widespread attention. Herein, carbon dots (C dots) decorated g-C3N4/TiO2 all-solid-state Z-scheme heterojunction photocatalysts with hierarchical macro/mesoporous structure have been fabricated via a facile solvothermal and calcination method. The dosage of C dots greatly influences the microstructure and the visible-light photocatalytic H2 evolution rate (HER). Under the optimal condition, the ternary composites consisting of C dots, g-C3N4 and TiO2 exhibited the highest HER of 580 μmol g−1 h−1, exceed the pure TiO2, pure g-C3N4 and the binary g-C3N4/TiO2 hybrid photocatalyst by a fact of 6.6 times, 2.1 times and 1.6 times, respectively. The excellent photocatalytic performance for hydrogen evolution is ascribed to the stronger light absorption, higher specific surface area and faster charge transportation. An all-solid-state Z-scheme heterojunction mechanism was proposed in which C dots serve as a mediator to improve the separation and transportation of photo-excited charge carriers.

Synthesis of ultrathin, nano-sized Ti3C2Tx with abundant =O and –OH terminals and high transparency as a cocatalyst: Enabling design of high-performance Titania-Ti3C2Tx hybrid photocatalysts

Conventional Ti3C2Tx used in photocatalysis usually has properties that are detrimental to the process such as thick layers, a micro-sized structure with low transparency, and a high concentration of fluorine terminals. Herein, we demonstrate the synthesis of ultrathin, nano-sized Ti3C2Tx with abundant oxygen-containing groups (=O and –OH) and high transparency (designated as N–Ti3C2Tx) as an alternative cocatalyst in liquid and gas phase photocatalysis. N–Ti3C2Tx is prepared by a two-step process that involves etching Al from Ti3AlC2 via fluorine treatment followed by simultaneous exfoliation and fluorine reduction. N–Ti3C2Tx is then coupled with TiO2 via hydration and dehydration approaches to form a photocatalyst (TiO2–N–Ti3C2Tx) with distinct morphology and surface chemistry. The small size of N–Ti3C2Tx facilitates a strong interfacial contact with TiO2, thereby enhancing electron transport between TiO2 and N–Ti3C2Tx, and electron-hole separation; and (2) the high transparency of N–Ti3C2Tx facilitates photon-TiO2 interactions. As a consequence, the photocatalytic activity of TiO2–N–Ti3C2Tx is superior to that of pristine TiO2, TiO2 coupled with thin, micro-sized Ti3C2Tx that is characterized by low transparency and fluorine terminals, and the widely used Ti3C2Tx-based photocatalyst synthesized by thermal nucleation of TiO2 on Ti3C2Tx. The high photocatalytic activity of TiO2–N–Ti3C2Tx is also attributed to the presence of abundant = O and –OH terminals on N–Ti3C2Tx that boosts pollutant adsorption. The study provides a rational approach for coupling TiO2 and Ti3C2Tx to promote beneficial charge transfer properties and synergistic effects that have far-reaching applications in photocatalysis.

One-step fluorine-free synthesis of delaminated, OH-terminated Ti3C2: High photocatalytic NOx storage selectivity enabled by coupling TiO2 and Ti3C2-OH

Difficulties associated with MXene fabrication typified by an environmentally hazardous fluorine-based etching process followed by delamination and fluorine reduction steps create obstacles against the expansion of this outstanding material and its application in air purification. Herein, we demonstrate a one-step hydrothermal process that involves alkali (NaOH)-assisted aluminum etching in the presence of a delaminating agent (hydrazine) for synthesis of delaminated, OH-terminated MXene (Ti3C2-OH). The process does not require the use of fluorine-containing compounds and produces Ti3C2-OH sheets without the need for post-synthesis treatment. Ti3C2-OH shows a strong synergistic effect as a co-catalyst when coupled with TiO2 during photocatalytic oxidation of NOx. Excellent NOx storage selectivity (91 %) and a positive DeNOx index (+ 0.30) were achieved at NO conversion of 54 %. The photocatalytic activity of the hybrid shows high sensitivity to the surface chemistry of the co-catalyst as Ti3C2-OH outperforms delaminated, F-terminated Ti3C2 (fabricated via the traditional process), which shows low NOx storage selectivity (65 %) and a negative DeNOx index (−0.05) at NO conversion of 47 %. We envision that these findings will benefit ongoing efforts aimed at developing effective alternative methods for MXene synthesis and provide a pathway for rational design of efficient NOx abatement photocatalysts.

Preparation of TiO2–MoO3 composite nanofibers by water-based electrospinning process and their application in photocatalysis

Coupling TiO2 nanofibers with other semiconductor metal oxides can effectively extend the light absorbability of TiO2 to the visible range of the electromagnetic spectrum. This study demonstrates the synthesis of TiO2–MoO3 composite nanofibers via electrospinning using Ti and Mo water-soluble precursors. Aqueous solutions of these precursors were added to a PVP solution in N–N dimethylformamide. The mixture was electrospun, followed by annealing in air at 600 °C obtaining oxide nanofibers. The fibers were characterized via thermogravimetry and differential thermal analysis, X-ray photoelectron spectroscopy, scanning electron microscopy and energy-dispersive X-ray spectroscopy, transmission electron microscopy, Fourier-transform infrared spectroscopy, X-ray diffraction, and Raman spectroscopy. The diameter of the TiO2–MoO3 fibers was between 90 and 110 nm after annealing, Furthermore, methylene blue dye was used to investigate the photocatalytic activity of the fibers in visible light. TiO2–MoO3 fibers showed the best photocalaytic activity with a rate constant of 0.0018 min−1 while pure TiO2 and MoO3 nanofibers had 0.0009 min−1 and 0.0008 min−1 respectively.

Polymeric viologen-based electron transfer mediator for improving the photoelectrochemical water splitting on Sb2Se3 photocathode

The photogenerated charge carrier separation and transportation of inside photocathodes can greatly influence the performance of photoelectrochemical (PEC) H2 production devices. Coupling TiO2 with p-type semiconductors to construct heterojunction structures is one of the most widely used strategies to facilitate charge separation and transportation. However, the band position of TiO2 could not perfectly match with all p-type semiconductors. Here, taking antimony selenide (Sb2Se3) as an example, a rational strategy was developed by introducing a viologen electron transfer mediator (ETM) containing polymeric film (poly-1,1′-dially-[4,4′-bipyridine]-1,1′-diium, denoted as PV2+) at the interface between Sb2Se3 and TiO2 to regulate the energy band alignment, which could inhibit the recombination of photogenerated charge carriers of interfaces. With Pt as a catalyst, the constructed Sb2Se3/PV2+/TiO2/Pt photocathode showed a superior PEC hydrogen generation activity with a photocurrent density of −18.6 mA cm−2 vs. a reversible hydrogen electrode (RHE) and a half-cell solar-to-hydrogen efficiency (HC-STH) of 1.54% at 0.17 V vs. RHE, which was much better than that of the related Sb2Se3/TiO2/Pt photocathode without PV2+ (−9.8 mA cm−2, 0.51% at 0.10 V vs. RHE).

Parasitic Light Absorption, Rate Laws and Heterojunctions in the Photocatalytic Oxidation of Arsenic(III) Using Composite TiO2 /Fe2 O3.

Composite photocatalyst‐adsorbents such as TiO2/Fe2O3 are promising materials for the one‐step treatment of arsenite contaminated water. However, no previous study has investigated how coupling TiO2 with Fe2O3 influences the photocatalytic oxidation of arsenic(III). Herein, we develop new hybrid experiment/modelling approaches to study light absorption, charge carrier behaviour and changes in the rate law of the TiO2/Fe2O3 system, using UV‐Vis spectroscopy, transient absorption spectroscopy (TAS), and kinetic analysis. Whilst coupling TiO2 with Fe2O3 improves total arsenic removal by adsorption, oxidation rates significantly decrease (up to a factor of 60), primarily due to the parasitic absorption of light by Fe2O3 (88 % of photons at 368 nm) and secondly due to changes in the rate law from disguised zero‐order kinetics to first‐order kinetics. Charge transfer across this TiO2‐Fe2O3 heterojunction is not observed. Our study demonstrates the first application of a multi‐adsorbate surface complexation model (SCM) towards describing As(III) oxidation kinetics which, unlike Langmuir‐Hinshelwood kinetics, includes the competitive adsorption of As(V). We further highlight the importance of parasitic light absorption and catalyst fouling when designing heterogeneous photocatalysts for As(III) remediation.

Exploring the photocatalytic activities of a highly {0 0 1} faceted TiO2 sensitized by coupling with AgBr or Ag3PO4

TiO2 with high {001} facet exposure was coupled with AgBr or Ag3PO4. Catalysts were widely characterized and tested with rhodamine B (RhB) or caffeic acid under UV and visible light. Combination of the used sensitizer (AgBr or Ag3PO4) with TiO2, not only enhances the high photocatalytic activity shown in the UV for TiO2, but it also largely increases the degradation activity under visible illumination. A synergistic effect toward photocatalytic degradation in the visible light was observed when coupling AgBr and TiO2, with the photocatalytic degradation profiles being strongly related to the molar percentages of the coupled materials and to the nature of the contaminant. The recycling of the coupled materials allows us to conclude that the AgBr(50%)/TiO2 sample presents better results in the consecutive reuse cycles and percentages of RhB dye mineralization, in contrast to those observed for the Ag3PO4(50%)/TiO2 composite.

Thermal Treatment of Polyvinyl Alcohol for Coupling MoS2 and TiO2 Nanotube Arrays toward Enhancing Photoelectrochemical Water Splitting Performance

Solar-driven photoelectrochemical (PEC) water splitting, using semiconductor photoelectrodes, is considered a promising renewable energy source and solution for environmental sustainability. Herein, we report polyvinyl alcohol (PVA) as a binder material for combining MoS2 and TiO2 nanotube arrays (TNAs) to improve PEC water splitting ability. By a thermal treatment process, the formation of the π conjunction in the PVA structure enhanced the PEC performance of MoS2/TNAs, exhibiting linear sweeps in an anodic direction with the current density over 65 μA/cm2 at 0 V vs. Ag/AgCl. Besides, the photoresponse ability of MoS2/TNAs is approximately 6-fold more significant than that of individual TNAs. Moreover, a Tafel slope of 140.6 mV/decade has been obtained for the oxygen evolution reaction (OER) of MoS2/TNAs materials.