Catalysts

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4 pages, 204 KiB

Open AccessEditorial

Editorial Catalysts: Special Issue on Recent Advances in TiO₂ Photocatalysts

by Anna Malankowska, Ewa Borowska, Rui C. Martins and Marta Gmurek

Catalysts 2021, 11(7), 790; https://doi.org/10.3390/catal11070790 - 29 Jun 2021

Cited by 5 | Viewed by 2730

Abstract

The development of civilization and the massive use of traditional energy sources has led to progressive environmental degradation that requires immediate action [...] Full article

(This article belongs to the Special Issue Recent Advances in TiO2 Photocatalysts)

Research

Jump to: Editorial, Review

14 pages, 2749 KiB

Open AccessArticle

Gas-Phase TiO₂ Photosensitized Mineralization of Some VOCs: Mechanistic Suggestions through a Langmuir–Hinshelwood Kinetic Approach

by Marta Bettoni, Stefano Falcinelli, Cesare Rol, Marzio Rosi and Giovanni Vittorio Sebastiani

Catalysts 2021, 11(1), 20; https://doi.org/10.3390/catal11010020 - 26 Dec 2020

Cited by 16 | Viewed by 2975

Abstract

A jointed experimental and theoretical investigation pointing out new insights about the microscopic mechanism of the volatile organic compounds (VOCs) photocatalytic elimination by TiO₂ was done. Methane, hexane, isooctane, acetone and methanol were photomineralized in a batch reactor. Values of K (adsorption [...] Read more.

A jointed experimental and theoretical investigation pointing out new insights about the microscopic mechanism of the volatile organic compounds (VOCs) photocatalytic elimination by TiO₂ was done. Methane, hexane, isooctane, acetone and methanol were photomineralized in a batch reactor. Values of K (adsorption constant on TiO₂) and k (mineralization rate constant) of the five VOCs (treating the kinetic data through a Langmuir–Hinshelwood approach) were determined. Recorded K (in the range of 0.74 × 10⁻²–1.11 × 10⁻² ppm⁻¹) and k (in the range of 1.9–9.9 ppm min⁻¹) values and performed theoretical calculations allowed us to suggest the involvement of an electron transfer step between the VOC and the hole, TiO₂(h⁺), as the rate-determining one. Full article

(This article belongs to the Special Issue Recent Advances in TiO2 Photocatalysts)

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14 pages, 5210 KiB

Open AccessArticle

Fabrication of a Cu₂O-Au-TiO₂ Heterostructure with Improved Photocatalytic Performance for the Abatement of Hazardous Toluene and α-Pinene Vapors

by Joon Yeob Lee and Jeong-Hak Choi

Catalysts 2020, 10(12), 1434; https://doi.org/10.3390/catal10121434 - 8 Dec 2020

Cited by 7 | Viewed by 2651

Abstract

In the current research, a Cu₂O-Au-TiO₂ heterostructure was fabricated via a step-wise photodeposition route to determine its possible application in the photocatalytic oxidation of hazardous vapors. The results of electron microscopy and X-ray photoelectron spectroscopy confirm the successful fabrication of [...] Read more.

In the current research, a Cu₂O-Au-TiO₂ heterostructure was fabricated via a step-wise photodeposition route to determine its possible application in the photocatalytic oxidation of hazardous vapors. The results of electron microscopy and X-ray photoelectron spectroscopy confirm the successful fabrication of the Cu₂O-Au-TiO₂ heterostructure. Strong absorption in the visible region, along with a slight red-shift in the absorption edge, was observed in the UV–vis diffuse reflectance spectrum of Cu₂O-Au-TiO₂ composite, which implies that the composite can generate a greater number of photoexcited charges necessary for photocatalytic reaction. Toluene and α-pinene, as common gas contaminants in the indoor atmosphere, were employed to assess the photooxidation efficiency of the Cu₂O-Au-TiO₂ composite. Importantly, photocatalytic activity results indicate that the Cu₂O-Au-TiO₂ composite showed excellent photodegradation performance compared to pure TiO₂ and Cu₂O-TiO₂ and Au-TiO₂, where photocatalytic efficiency was approximately 92.9% and 99.9% for toluene and α-pinene, respectively, under standard daylight illumination. The increased light-harvesting capacity and boosted separation efficiency of electron-hole pairs were mainly accountable for improved degradation performance of the Cu₂O-Au-TiO₂ composite. In addition, the degradation efficiencies for toluene and α-pinene by the Cu₂O-Au-TiO₂ composite were also examined under three different light sources: 0.32 W white, blue and violet LEDs. The findings of this work suggested a great promise of effective photooxidation of gas pollutants by the Cu₂O-Au-TiO₂ composite. Full article

(This article belongs to the Special Issue Recent Advances in TiO2 Photocatalysts)

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16 pages, 3802 KiB

Open AccessArticle

Experimental and Computational Analysis of NO_x Photocatalytic Abatement Using Carbon-Modified TiO₂ Materials

by Tatiana Zhiltsova., Nelson Martins, Mariana R. F. Silva, Carla F. Da Silva, Mirtha A. O. Lourenço, David M. Tobaldi, Daniel Covita, Maria Paula Seabra and Paula Ferreira

Catalysts 2020, 10(12), 1366; https://doi.org/10.3390/catal10121366 - 24 Nov 2020

Cited by 4 | Viewed by 3297

Abstract

In the present study, two photocatalytic graphene oxide (GO) and carbon nanotubes (CNT) modified TiO₂ materials thermally treated at 300 °C (T300_GO and T300_CNT, respectively) were tested and revealed their conversion efficiency of nitrogen oxides (NO_x) under simulated solar light, [...] Read more.

In the present study, two photocatalytic graphene oxide (GO) and carbon nanotubes (CNT) modified TiO₂ materials thermally treated at 300 °C (T300_GO and T300_CNT, respectively) were tested and revealed their conversion efficiency of nitrogen oxides (NO_x) under simulated solar light, showing slightly better results when compared with the commercial Degussa P25 material at the initial concentration of NO_x of 200 ppb. A chemical kinetic model based on the Langmuir–Hinshelwood (L-H) mechanism was employed to simulate micropollutant abatement. Modeling of the fluid dynamics and photocatalytic oxidation (PCO) kinetics was accomplished with computational fluid dynamics (CFD) approach for modeling single-phase liquid fluid flow (air/NO_x mixture) with an isothermal heterogeneous surface reaction. A tuning methodology based on an extensive CFD simulation procedure was applied to adjust the kinetic model parameters toward a better correspondence between simulated and experimentally obtained data. The kinetic simulations of heterogeneous photo-oxidation of NO_x carried out with the optimized parameters demonstrated a high degree of matching with the experimentally obtained NO_x conversion. T300_CNT is the most active photolytic material with a degradation rate of 62.1%, followed by P25-61.4% and T300_GO-60.4%, when irradiated, for 30 min, with emission spectra similar to solar light. Full article

(This article belongs to the Special Issue Recent Advances in TiO2 Photocatalysts)

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16 pages, 3336 KiB

Open AccessArticle

Visible-Light Photocatalytic Degradation of Aniline Blue by Stainless-Steel Foam Coated with TiO₂ Grafted with Anthocyanins from a Maqui-Blackberry System

by Dreidy Vásquez, Francisca Palominos and Sebastián Martínez

Catalysts 2020, 10(11), 1245; https://doi.org/10.3390/catal10111245 - 28 Oct 2020

Cited by 11 | Viewed by 3985

Abstract

Anthocyanins from maqui (Aristotelia chilensis) and blackberry (Rubus glaucus) were used as light harvesters to improve the photocatalytic activity of titanium dioxide in visible light. Anthocyanins from both species were obtained using high-frequency ultrasound-assisted liquid-liquid extraction with methanol. Mixtures [...] Read more.

Anthocyanins from maqui (Aristotelia chilensis) and blackberry (Rubus glaucus) were used as light harvesters to improve the photocatalytic activity of titanium dioxide in visible light. Anthocyanins from both species were obtained using high-frequency ultrasound-assisted liquid-liquid extraction with methanol. Mixtures of anthocyanins were developed to study their effectiveness in the visible light/TiO₂ reaction for the oxidation of aniline blue. For this purpose, stainless-steel foams were covered with TiO₂ and anthocyanin and characterized by SEM. Different samples were fabricated by varying the ratio of the two anthocyanins in the mixture (100, 75, 50, 25 and 0 vol% of maqui-anthocyanin (delphinidin)). The mixtures of 25 vol% anthocyanin from maqui and 75 vol% anthocyanin from blackberry had higher total anthocyanin content and better photocatalytic activity in visible light: degradation of aniline blue was 40% at pH 7, 56% at pH 3 and 95% at pH 3 with the injection of oxygen for 2 h in comparison with TiO₂-foam/UV light, which yielded values of 13% at pH 7 and 73% at pH 3 with and without the addition of oxygen. Natural dyes that are low-cost and environmentally friendly substances are shown to be capable of improving the visible-light photocatalytic activity of TiO₂. Full article

(This article belongs to the Special Issue Recent Advances in TiO2 Photocatalysts)

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9 pages, 2387 KiB

Open AccessArticle

Large-Area Patterning of Oil-Based Inks on Superhydrophobic TiO₂ Nanotubular Layers by Photocatalytic Wettability Conversion

by Jiao Jin, Huihui Ren and Zhaoyue Liu

Catalysts 2020, 10(10), 1203; https://doi.org/10.3390/catal10101203 - 17 Oct 2020

Cited by 3 | Viewed by 2210

Abstract

Patterning an oil-based ink on a solid surface based on a wettability difference is of significant importance for the application of offset printing. Herein, we describe a large-area patterning of oil-based ink on a self-organized TiO₂ nanotubular layer based on a photocatalytic [...] Read more.

Patterning an oil-based ink on a solid surface based on a wettability difference is of significant importance for the application of offset printing. Herein, we describe a large-area patterning of oil-based ink on a self-organized TiO₂ nanotubular layer based on a photocatalytic wettability conversion. The TiO₂ nanotubular layer was fabricated by electrochemical anodization, which demonstrated a superhydrophobic wettability after modification with a self-assembled molecular layer. Subsequently, area-selective ultraviolet (UV) irradiation through a pre-designed pattern of water-based UV-resistant ink formed by an ink-jet technique was used to form a wettability difference. After removing the water-based ink, an oil-based ink was capable of depositing selectively on the superhydrophobic area to form the same pattern as the pre-designed pattern of water-based ink. This large-area patterning of an oil-based ink based on the photocatalytic wettability conversion is potentially applicable in offset printing. Full article

(This article belongs to the Special Issue Recent Advances in TiO2 Photocatalysts)

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21 pages, 5519 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Exploring the Photothermo-Catalytic Performance of Brookite TiO₂-CeO₂ Composites

by Marianna Bellardita, Roberto Fiorenza, Luisa D'Urso, Luca Spitaleri, Antonino Gulino, Giuseppe Compagnini, Salvatore Scirè and Leonardo Palmisano

Catalysts 2020, 10(7), 765; https://doi.org/10.3390/catal10070765 - 9 Jul 2020

Cited by 42 | Viewed by 4699

Abstract

The thermocatalytic, photocatalytic and photothermo-catalytic oxidation of some volatile organic compounds (VOCs), 2-propanol, ethanol and toluene, was investigated over brookite TiO₂-CeO₂ composites. The multi-catalytic approach based on the synergistic effect between solar photocatalysis and thermocatalysis led to the considerable decrease [...] Read more.

The thermocatalytic, photocatalytic and photothermo-catalytic oxidation of some volatile organic compounds (VOCs), 2-propanol, ethanol and toluene, was investigated over brookite TiO₂-CeO₂ composites. The multi-catalytic approach based on the synergistic effect between solar photocatalysis and thermocatalysis led to the considerable decrease in the conversion temperatures of the organic compounds. In particular, in the photothermo-catalytic runs, for the most active samples (TiO₂-3 wt% CeO₂ and TiO₂-5 wt% CeO₂), the temperature at which 90% of VOC conversion occurred was about 60 °C, 40 °C and 20 °C lower than in the thermocatalytic tests for 2-propanol, ethanol and toluene, respectively. Furthermore, the addition of cerium oxide to brookite TiO₂ favored the total oxidation to CO₂ already in the photocatalytic tests at room temperature. The presence of small amounts of cerium oxide allowed to obtain efficient brookite-based composites facilitating the space charge separation and increasing the lifetime of the photogenerated holes and electrons as confirmed by the characterization measurements. The possibility to concurrently utilize the photocatalytic properties of brookite and the redox properties of CeO₂, both activated in the photothermal tests, is an attractive approach easily applicable to purify air from VOCs. Full article

(This article belongs to the Special Issue Recent Advances in TiO2 Photocatalysts)

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11 pages, 2677 KiB

Open AccessArticle

Enhanced Photocatalytic CO₂ Reduction over TiO₂ Using Metalloporphyrin as the Cocatalyst

by Ziyi Wang, Wei Zhou, Xin Wang, Xueliang Zhang, Huayu Chen, Huilin Hu, Lequan Liu, Jinhua Ye and Defa Wang

Catalysts 2020, 10(6), 654; https://doi.org/10.3390/catal10060654 - 11 Jun 2020

Cited by 38 | Viewed by 4879

Abstract

The photocatalytic reduction of carbon dioxide (CO₂) into CO and hydrocarbon fuels has been considered as an ideal green technology for solar-to-chemical energy conversion. The separation/transport of photoinduced charge carriers and adsorption/activation of CO₂ molecules play crucial roles in photocatalytic [...] Read more.

The photocatalytic reduction of carbon dioxide (CO₂) into CO and hydrocarbon fuels has been considered as an ideal green technology for solar-to-chemical energy conversion. The separation/transport of photoinduced charge carriers and adsorption/activation of CO₂ molecules play crucial roles in photocatalytic activity. Herein, tetrakis (4-carboxyphenyl) porphyrin (H₂TCPP) was incorporated with different metal atoms in the center of a conjugate macrocycle, forming the metalloporphyrins TCPP-M (M = Co, Ni, Cu). The as-obtained metalloporphyrin was loaded as a cocatalyst on commercial titania (P25) to form TCPP-M@P25 (M = Co, Ni, Cu) for enhanced CO₂ photoreduction. Among all of the TCPP-M@P25 (M = Co, Ni, Cu), TCPP-Cu@P25 exhibited the highest evolution rates of CO (13.6 μmol⋅g⁻¹⋅h⁻¹) and CH₄ (1.0 μmol⋅g⁻¹⋅h⁻¹), which were 35.8 times and 97.0 times those of bare P25, respectively. The enhanced photocatalytic activity could be attributed to the improved photogenerated electron-hole separation efficiency, as well as the increased adsorption/activation sites provided by the metal centers in TCPP-M (M = Co, Ni, Cu). Our study indicates that metalloporphyrin could be used as a high-efficiency cocatalyst to enhance CO₂ photoreduction activity. Full article

(This article belongs to the Special Issue Recent Advances in TiO2 Photocatalysts)

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16 pages, 92929 KiB

Open AccessArticle

Industrial Textile Wastewater Ozone Treatment: Catalyst Selection

by Lucyna Bilińska, Kazimierz Blus, Magdalena Bilińska and Marta Gmurek

Catalysts 2020, 10(6), 611; https://doi.org/10.3390/catal10060611 - 1 Jun 2020

Cited by 22 | Viewed by 4444

Abstract

One of the recent trends in textile wastewater treatment has become catalytic ozonation. The necessity of effective color removal in a short treatment time is a standard during industrial implementation. At the same time, efficient chemical oxygen demand (COD), total organic carbon (TOC), [...] Read more.

One of the recent trends in textile wastewater treatment has become catalytic ozonation. The necessity of effective color removal in a short treatment time is a standard during industrial implementation. At the same time, efficient chemical oxygen demand (COD), total organic carbon (TOC), and toxic by-product removal are highly expected. This study presents the results of a catalytic ozonation treatment. Three types of catalysts: a metal oxide (TiO₂ as P25 by Degussa), activated carbon (nano-powder by Sigma, AC), and metal particles (platinum, 1% wt. supported on AC matrix by Sigma, Pt–AC) have been applied. The investigations were conducted for real industrial wastewater originated in textile dyeing with Reactive Black 5 dye (RB5). The experiments ran for the raw wastewater (without pretreatment), exposed blocking of the catalytic action by all used catalysts. The catalytic effect could be observed when catalytic ozonation was used as a polishing step after electrocoagulation (EC). Although the catalytic effect could be observe for all catalysts then, especially in the removal of colorless by-products, the AC was exposed as the most effective. This contributed to 35% and 40% of TOC and COD removal. While only 18% and 23% of TOC and COD were removed in the same process without AC. The decrease in toxicity was 30%. The results of the study revealed the complexity of the issue and resulted in an extensive discussion devoted to the basis of the catalytic activity of each catalyst. Full article

(This article belongs to the Special Issue Recent Advances in TiO2 Photocatalysts)

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14 pages, 6139 KiB

Open AccessArticle

Synthesis of Conducting Bifunctional Polyaniline@Mn-TiO₂ Nanocomposites for Supercapacitor Electrode and Visible Light Driven Photocatalysis

by Milan Babu Poudel, Changho Yu and Han Joo Kim

Catalysts 2020, 10(5), 546; https://doi.org/10.3390/catal10050546 - 14 May 2020

Cited by 87 | Viewed by 6284

Abstract

We report a polyaniline-wrapped, manganese-doped titanium oxide (PANi/Mn-TiO₂) nanoparticle composite for supercapacitor electrode and photocatalytic degradation. The PANi/Mn-TiO₂ nanoparticles were synthesized using a solvothermal process, followed by oxidative polymerization of aniline. The structural properties of studied materials were confirmed by [...] Read more.

We report a polyaniline-wrapped, manganese-doped titanium oxide (PANi/Mn-TiO₂) nanoparticle composite for supercapacitor electrode and photocatalytic degradation. The PANi/Mn-TiO₂ nanoparticles were synthesized using a solvothermal process, followed by oxidative polymerization of aniline. The structural properties of studied materials were confirmed by XRD, FTIR, HRTEM, FESEM, and UV visible spectroscopy. The as-prepared PANi/Mn-TiO₂ nanoparticles revealed admirable electrochemical performance with a specific capacitance of 635.87 F g⁻¹ at a current density of 1 A g⁻¹ with a notable life cycle retention of 91% after 5000 charge/discharge cycles. Furthermore, the asymmetric cell with PANi/Mn-TiO₂ as a positive electrode exhibited energy density of 18.66 W h kg⁻¹ with excellent stability. Moreover, the PANi/Mn-TiO₂ had promising photocatalytic activity for methylene blue degradation. The improved performance of PANi/Mn-TiO₂ nanoparticles is attributed to the well-built synergetic effect of components that lead to significant reduction of band gap energy and charge transfer resistance, as revealed by UV visible spectroscopy and electrochemical impedance spectroscopy. Full article

(This article belongs to the Special Issue Recent Advances in TiO2 Photocatalysts)

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14 pages, 3548 KiB

Open AccessArticle

Biomorphic Fibrous TiO₂ Photocatalyst Obtained by Hydrothermal Impregnation of Short Flax Fibers with Titanium Polyhydroxocomplexes

by Mikhail F. Butman, Nataliya E. Kochkina, Nikolay L. Ovchinnikov, Nikolay V. Zinenko, Dmitry N. Sergeev and Michael Müller

Catalysts 2020, 10(5), 541; https://doi.org/10.3390/catal10050541 - 13 May 2020

Cited by 8 | Viewed by 2750

Abstract

A biomimetic solution technology for producing a photocatalytic material in the form of biomorphic titanium oxide fibers with a hierarchical structure using short flax fiber as a biotemplate is proposed. The impregnation of flax fibers intensified under hydrothermal conditions with a precursor was [...] Read more.

A biomimetic solution technology for producing a photocatalytic material in the form of biomorphic titanium oxide fibers with a hierarchical structure using short flax fiber as a biotemplate is proposed. The impregnation of flax fibers intensified under hydrothermal conditions with a precursor was performed in an autoclave to activate the nucleation of the photoactive TiO₂ phases. The interaction between precursor and flax fibers was studied by using infrared spectroscopy (IR) and differential scanning calorimetry/thermogravimetry analysis (DSC/TG). The morphology, structure, and textural properties of the TiO₂ fibers obtained at annealing temperatures of 500–700 °C were determined by X-ray diffraction analysis, scanning electron microscopy, and nitrogen adsorption/desorption. It is shown that the annealing temperature of the impregnated biotemplates significantly affects the phase composition, crystallite size, and porous structure of TiO₂ fiber samples. The photocatalytic activity of the obtained fibrous TiO₂ materials was evaluated by using the decomposition of the cationic dye Rhodamine B in an aqueous solution (concentration 12 mg/L) under the influence of ultraviolet radiation (UV). The maximum photodegradation efficiency of the Rhodamine B was observed for TiO₂ fibers annealed at 600 °C and containing 40% anatase and 60% rutile. This sample ensured 100% degradation of the dye in 20 min, and this amount significantly exceeds the photocatalytic activity of the commercial Degussa P25 photocatalyst and TiO₂ samples obtained previously under hydrothermal conditions by the sol-gel method. Full article

(This article belongs to the Special Issue Recent Advances in TiO2 Photocatalysts)

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13 pages, 3352 KiB

Open AccessArticle

Photocatalytic Oxidative Degradation of Carbamazepine by TiO₂ Irradiated by UV Light Emitting Diode

by Zhilin Ran, Yuanhang Fang, Jian Sun, Cong Ma and Shaofeng Li

Catalysts 2020, 10(5), 540; https://doi.org/10.3390/catal10050540 - 13 May 2020

Cited by 21 | Viewed by 4085

Abstract

Here, ultraviolet light-emitting diodes (UV-LED) combined with TiO₂ was used to investigate the feasibility of carbamazepine (CBZ) degradation. The effects of various factors, like crystal form of the catalyst (anatase, rutile, and mixed phase), mass concentration of TiO₂, wavelength and [...] Read more.

Here, ultraviolet light-emitting diodes (UV-LED) combined with TiO₂ was used to investigate the feasibility of carbamazepine (CBZ) degradation. The effects of various factors, like crystal form of the catalyst (anatase, rutile, and mixed phase), mass concentration of TiO₂, wavelength and irradiation intensity of the UV-LED light source, pH of the reaction system, and coexisting anions and cations, on the photocatalytic degradation of CBZ were studied. The mixed-phase (2.8 g/L) showed the best degradation efficiency at 365 nm among three kinds of TiO₂, wherein CBZ (21.1 µM) was completely oxidized within 1 h. The results of batch experiments showed that: (i) CBZ degradation efficiency under UV-LED light at 365 nm was higher than 275 nm, due to stronger penetrability of 365 nm light in solution. (ii) The degradation efficiency increased with increase in irradiation intensity and pH, whereas it decreased with increase in initial CBZ concentration. (iii) The optimal amount of mixed-phase TiO₂ catalyst was 2.8 g/L and excessive catalyst decreased the rate. (iv) The co-existence of CO₃²⁻, HCO₃⁻, and Fe³⁺ ions in water significantly accelerated the degradation rate of photocatalytic CBZ, whereas Cu²⁺ ions strongly inhibited the degradation process of CBZ. ·OH was found to be the main active species in the UV-LED photocatalytic degradation of CBZ. UV-LED is more environmentally friendly, energy efficient, and safer, whereas commercial TiO₂ is economical and readily available. Therefore, this study provides a practically viable reference method for the degradation of pharmaceuticals and personal care products (PPCPs). Full article

(This article belongs to the Special Issue Recent Advances in TiO2 Photocatalysts)

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20 pages, 4128 KiB

Open AccessArticle

Shape-Selective Mesoscale Nanoarchitectures: Preparation and Photocatalytic Performance

by Simona E. Hunyadi Murph and Katie Heruox

Catalysts 2020, 10(5), 532; https://doi.org/10.3390/catal10050532 - 12 May 2020

Cited by 13 | Viewed by 2486

Abstract

We create ordered arrays of shape-selective gold-titania composite nanomaterials at the mesoscale (100 µm to 5 mm) by a combination of both bottom-up and top-down approaches for exquisite control of the size, shape, and arrangement of nanomaterials. Lithographic techniques along with wet chemical [...] Read more.

We create ordered arrays of shape-selective gold-titania composite nanomaterials at the mesoscale (100 µm to 5 mm) by a combination of both bottom-up and top-down approaches for exquisite control of the size, shape, and arrangement of nanomaterials. Lithographic techniques along with wet chemical synthetic methods were combined to create these composite nanomaterials. The photocatalytic activity of these TiO_2, TiO₂-Au and SiO₂-TiO₂-Au nano-composite mesoscale materials was monitored by the photodegradation of a model analyte, methyl orange, under UV and visible (Vis) illumination. Bare TiO₂- and SiO₂-TiO₂-coated pillar arrays showed significant activity toward methyl orange in UV light with degradation rates on the order of 10⁻⁴–10⁻³ min⁻¹. The photocatalytic activity of these arrays was also found to depend on the nanoparticle shape, in which particles with more edges and corners were found to be more reactive than spherical particles (i.e., the photocatalytic activity decreased as follows: diamonds > squares > triangles > spheres). SiO₂-TiO₂-Au nano-composite pillar arrays were tested in both UV and Vis light and showed increased activity in Vis light but decreased activity in UV light as compared to the bare semiconductor arrays. Additionally, the Au nanorod-functionalized nanoarrays exhibit a strong shape-dependence in their photocatalytic activity toward methyl orange degradation in Vis light. Full article

(This article belongs to the Special Issue Recent Advances in TiO2 Photocatalysts)

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12 pages, 2472 KiB

Open AccessArticle

Investigation of the Synergistic Effect of Sonolysis and Photocatalysis of Titanium Dioxide for Organic Dye Degradation

by Yunseok Choi, Daein Lee, Sungje Hong, Sovann Khan, Burak Darya, Jae-Young Lee, Jaewon Chung and So-Hye Cho

Catalysts 2020, 10(5), 500; https://doi.org/10.3390/catal10050500 - 2 May 2020

Cited by 32 | Viewed by 5097

Abstract

Herein, we report the effect of sonoluminescence and an initial dye concentration on the sonophotocatalysis of TiO₂ for the degradation of eosin B, a textile dye. We first investigated the light illuminated during ultrasound irradiation (sonoluminescence) by photographic images, a radical indicator [...] Read more.

Herein, we report the effect of sonoluminescence and an initial dye concentration on the sonophotocatalysis of TiO₂ for the degradation of eosin B, a textile dye. We first investigated the light illuminated during ultrasound irradiation (sonoluminescence) by photographic images, a radical indicator (luminol), and photoluminescence spectra of the detection range of 300–1050 nm. Next, we examined the synergistic effect of sonolysis on photocatalysis by comparing the dye degradation of sonophotocatalysis to that of individual contributions of sonolysis and photocatalysis. Since it was found that the synergist effect is highly engaged with a dye concentration and sonication power, we conducted the comparison test in different concentrations of eosin B (5 and 20 mg/L) and ultrasound powers (35.4, 106.1, and 176.8 W/cm²). When the concentration of dyes was low, negative synergistic effects were found at all ultrasound powers, whereas at the high concentration, positive synergistic effects were observed at high ultrasound power. This difference in synergistic effects was explained by the influence of ultrasound on dynamics of dye adsorption on the TiO₂ surface. Full article

(This article belongs to the Special Issue Recent Advances in TiO2 Photocatalysts)

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16 pages, 3953 KiB

Open AccessArticle

Enhancement of Photocatalytic Oxidation of Glucose to Value-Added Chemicals on TiO₂ Photocatalysts by A Zeolite (Type Y) Support and Metal Loading

by Kamonchanok Roongraung, Surawut Chuangchote and Navadol Laosiripojana

Catalysts 2020, 10(4), 423; https://doi.org/10.3390/catal10040423 - 13 Apr 2020

Cited by 28 | Viewed by 4842

Abstract

TiO₂-based photocatalysts synthesized by the microwave-assisted sol-gel method was tested in the photocatalytic glucose conversion. Modifications of TiO₂ with type-Y zeolite (ZeY) and metals (Ag, Cu, and Ag-Cu) were developed for increasing the dispersion of TiO₂ nanoparticles and increasing [...] Read more.

TiO₂-based photocatalysts synthesized by the microwave-assisted sol-gel method was tested in the photocatalytic glucose conversion. Modifications of TiO₂ with type-Y zeolite (ZeY) and metals (Ag, Cu, and Ag-Cu) were developed for increasing the dispersion of TiO₂ nanoparticles and increasing the photocatalytic activity. Effects of the TiO₂ dosage to zeolite ratio (i.e., TiO₂/ZeY of 10, 20, 40, and 50 mol %) and the silica to alumina ratio in ZeY (i.e., SiO₂:Al₂O₃ of 10, 100, and 500) were firstly studied. It was found that the specific surface area of TiO₂/ZeY was 400–590 m²g⁻¹, which was higher than that of pristine TiO₂ (34.38 m²g⁻¹). The good properties of 20%TiO₂/ZeY photocatalyst, including smaller particles (13.27 nm) and high surface area, could achieve the highest photocatalytic glucose conversion (75%). Yields of gluconic acid, arabinose, xylitol, and formic acid obtained from 20%TiO₂/ZeY were 9%, 26%, 4%, and 35%, respectively. For the effect of the silica to alumina ratio, the highest glucose conversion was obtained from SiO₂:Al₂O₃ ratio of 100. Interestingly, it was found that the SiO₂:Al₂O₃ ratio affected the selectivity of carboxylic products (gluconic acid and formic acid). At a low ratio of silica to alumina (SiO₂:Al₂O₃ = 10), higher selectivity of the carboxylic products (gluconic acid = 29% and formic acid = 32%) was obtained (compared with other higher ratios). TiO₂/ZeY was further loaded by metals using the microwave-assisted incipient wetness impregnation technique. The highest glucose conversion of 96.9 % was obtained from 1 wt. % Ag-TiO₂ (40%)/ZeY. Furthermore, the bimetallic Ag-Cu-loaded TiO₂/ZeY presented the highest xylitol yield of 12.93%. Full article

(This article belongs to the Special Issue Recent Advances in TiO2 Photocatalysts)

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18 pages, 4522 KiB

Open AccessFeature PaperArticle

The Effect of AgInS₂, SnS, CuS₂, Bi₂S₃ Quantum Dots on the Surface Properties and Photocatalytic Activity of QDs-Sensitized TiO₂ Composite

by Anna Malankowska, Daria Kulesza, Jakub Sowik, Onur Cavdar, Tomasz Klimczuk, Grzegorz Trykowski and Adriana Zaleska-Medynska

Catalysts 2020, 10(4), 403; https://doi.org/10.3390/catal10040403 - 7 Apr 2020

Cited by 13 | Viewed by 4912

Abstract

The effect of type (AgInS₂, SnS, CuS₂, Bi₂S₃) and amount (5, 10, 15 wt%) of quantum dots (QDs) on the surface properties and photocatalytic activity of QDs-sensitized TiO₂ composite, was investigated. AgInS₂, [...] Read more.

The effect of type (AgInS₂, SnS, CuS₂, Bi₂S₃) and amount (5, 10, 15 wt%) of quantum dots (QDs) on the surface properties and photocatalytic activity of QDs-sensitized TiO₂ composite, was investigated. AgInS₂, SnS, CuS₂, Bi₂S₃ QDs were obtained by hot-injection, sonochemical, microwave, and hot-injection method, respectively. To characterize of as-prepared samples high-resolution transmission electron microscopy (HRTEM), scanning electron microscopy (SEM), X-ray diffraction (XRD), UV-Vis spectroscopy and photoluminescence (PL) emission spectroscopy were applied. The size of AgInS₂, SnS, CuS₂, Bi₂S₃ QDs were 12; 2–6; 2–3, and 1–2 nm, respectively. The QDs and QDs-sensitized TiO₂ composites obtained have been tested in toluene degradation under LEDs light irradiation (λ_max = 415 nm and λ_max = 375 nm). For pristine QDs the efficiency of toluene degradation increased in the order of AgInS₂ < Bi₂S₃ < CuS < SnS under 375 nm and AgInS₂ < CuS < Bi₂S₃ < SnS under 415 nm. In the presence of TiO₂/SnS QDs_15% composite, 91% of toluene was degraded after 1 h of irradiation, and this efficiency was about 12 higher than that for pristine QDs under 375 nm. Generally, building the TiO₂/AgInS₂ and TiO₂/SnS exhibited higher photoactivity under 375 nm than the pristine TiO₂ and QDs which suggests a synergistic effect between QDs and TiO₂ matrix. Full article

(This article belongs to the Special Issue Recent Advances in TiO2 Photocatalysts)

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12 pages, 2472 KiB

Open AccessArticle

Selective Oxidation of Crude Glycerol to Dihydroxyacetone in a Biphasic Photoreactor

by Alexander Luis Imbault and Ramin Farnood

Catalysts 2020, 10(4), 360; https://doi.org/10.3390/catal10040360 - 26 Mar 2020

Cited by 5 | Viewed by 4300

Abstract

In this paper, the first biphasic photoreactor was introduced and utilized for the conversion of glycerol to glyceraldehyde (GAD) and dihydroxyacetone (DHA) using water and ethyl acetate as dispersed (active) and continuous (inactive) phases, respectively. Increasing the ethyl acetate content in the reactor [...] Read more.

In this paper, the first biphasic photoreactor was introduced and utilized for the conversion of glycerol to glyceraldehyde (GAD) and dihydroxyacetone (DHA) using water and ethyl acetate as dispersed (active) and continuous (inactive) phases, respectively. Increasing the ethyl acetate content in the reactor improved the DHA yield; however, the optimal DHA selectivity was obtained at an ethyl acetate to water ratio of 90:10 (vol/vol). Compared to a monophasic photoreactor containing only water and identical amounts of glycerol and photocatalyst, the biphasic reactor containing 90 vol % ethyl acetate increased the DHA yield by a factor of 2.9 (from 4.5% to 13%) and the concentration of DHA by approximately 14 times (from 0.08 mM to 1.1 mM) after 240 min. Additionally, photocatalytic conversion of crude glycerol extracted using a 90:10 (vol/vol) ethyl acetate-water mixture showed a similar DHA conversion and yield to that of pure glycerol. Full article

(This article belongs to the Special Issue Recent Advances in TiO2 Photocatalysts)

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18 pages, 5324 KiB

Open AccessArticle

Synergistic Effect of Dielectric Barrier Discharge Plasma and TiO₂-Pillared Montmorillonite on the Degradation of Rhodamine B in an Aqueous Solution

by Mikhail F. Butman, Andrey A. Gushchin, Nikolay L. Ovchinnikov, Grigoriy I. Gusev, Nikolay V. Zinenko, Sofia P. Karamysheva and Karl W. Krämer

Catalysts 2020, 10(4), 359; https://doi.org/10.3390/catal10040359 - 25 Mar 2020

Cited by 34 | Viewed by 3707

Abstract

Photocatalytic, plasma and combined plasma–photocatalytic processes were applied for the destruction of a model pollutant, Rhodamine B dye, in an aqueous solution (concentration of 40 mg/L). For this purpose TiO₂-pillared montmorillonite was used as a photocatalyst (characterized by X-ray analysis and [...] Read more.

Photocatalytic, plasma and combined plasma–photocatalytic processes were applied for the destruction of a model pollutant, Rhodamine B dye, in an aqueous solution (concentration of 40 mg/L). For this purpose TiO₂-pillared montmorillonite was used as a photocatalyst (characterized by X-ray analysis and low-temperature nitrogen adsorption/desorption). It was prepared by the method of intercalation of titanium hydroxocomplexes, including hydrothermal activation of the process and preliminary mechanical treatment of the layered substrate. The dielectric barrier discharge (DBD) plasma in the presence of photocatalysts increases the efficiency of dye degradation (100%, 8 s) compared to plasmolysis (94%) and UV photolysis (92%, 100 min of UV irradiation); in contrast to photolysis, destructive processes are more profound and lead to the formation of simple organic compounds such as carboxylic acids. The plasma–catalytic method enhances by 20% the energetic efficiency of the destruction of Rhodamine B compared to DBD plasma. The efficiency of dye destruction with the plasma–catalytic method increases with the improvement of the textural properties of the photocatalyst. Full article

(This article belongs to the Special Issue Recent Advances in TiO2 Photocatalysts)

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16 pages, 3736 KiB

Open AccessArticle

Core-Shell Nanostructures of Graphene-Wrapped CdS Nanoparticles and TiO₂ (CdS@G@TiO₂): The Role of Graphene in Enhanced Photocatalytic H₂ Generation

by Muhammad Zubair, Ingeborg-Helene Svenum, Magnus Rønning and Jia Yang

Catalysts 2020, 10(4), 358; https://doi.org/10.3390/catal10040358 - 25 Mar 2020

Cited by 31 | Viewed by 5244

Abstract

Aiming to achieve enhanced photocatalytic activity and stability toward the generation of H₂ from water, we have synthesized noble metal-free core-shell nanoparticles of graphene (G)-wrapped CdS and TiO₂ (CdS@G@TiO₂) by a facile hydrothermal method. The interlayer thickness of G [...] Read more.

Aiming to achieve enhanced photocatalytic activity and stability toward the generation of H₂ from water, we have synthesized noble metal-free core-shell nanoparticles of graphene (G)-wrapped CdS and TiO₂ (CdS@G@TiO₂) by a facile hydrothermal method. The interlayer thickness of G between the CdS core and TiO₂ shell is optimized by varying the amount of graphene quantum dots (GQD) during the synthesis procedure. The most optimized sample, i.e., CdS@50G@TiO₂ generated 1510 µmole g⁻¹ h⁻¹ of H₂ (apparent quantum efficiency (AQE) = 5.78%) from water under simulated solar light with air mass 1.5 global (AM 1.5G) condition which is ~2.7 times and ~2.2 time superior to pure TiO₂ and pure CdS respectively, along with a stable generation of H₂ during 40 h of continuous operation. The increased photocatalytic activity and stability of the CdS@50G@TiO₂ sample are attributed to the enhanced visible light absorption and efficient charge separation and transfer between the CdS and TiO₂ due to incorporation of graphene between the CdS core and TiO₂ shell, which was also confirmed by UV-vis, photoelectrochemical and valence band XPS measurements. Full article

(This article belongs to the Special Issue Recent Advances in TiO2 Photocatalysts)

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19 pages, 2851 KiB

Open AccessArticle

Development and Validation of a LC-MS/MS Method for Determination of Multi-Class Antibiotic Residues in Aquaculture and River Waters, and Photocatalytic Degradation of Antibiotics by TiO₂ Nanomaterials

by Tho Chau Minh Vinh Do, Duy Quoc Nguyen, Tuan Duc Nguyen and Phuoc Huu Le

Catalysts 2020, 10(3), 356; https://doi.org/10.3390/catal10030356 - 24 Mar 2020

Cited by 35 | Viewed by 6702

Abstract

This study presents a multi-residue method for simultaneous qualitative and quantitative analysis of eight antibiotics from some common classes, including beta-lactam, tetracyclines, lincosamides, glycopeptides, and sulfonamides in 39 aquaculture and river water samples from the Mekong Delta (Vietnam) using liquid chromatography-tandem mass spectrometry [...] Read more.

This study presents a multi-residue method for simultaneous qualitative and quantitative analysis of eight antibiotics from some common classes, including beta-lactam, tetracyclines, lincosamides, glycopeptides, and sulfonamides in 39 aquaculture and river water samples from the Mekong Delta (Vietnam) using liquid chromatography-tandem mass spectrometry (LC-MS/MS). As a result, doxycycline (DXC), oxytetracycline (OTC), lincomycin (LCM), sulfamethoxazole (SMX), and sulfamethazine (SMZ) were detected with high frequency over 65% and an average concentration of 22.6–76.8 ng·mL⁻¹. The result suggests that antibiotic residues in the aquaculture and river waters are considered as an emerging environmental problem of the region. To address this issue, we fabricated the well-defined TiO₂ nanotube arrays (TNAs) and nanowires on nanotube arrays (TNWs/TNAs) using the anodization method. The TNAs had an inner tube diameter of ~95 nm and a wall thickness of ~25 nm. Meanwhile, the TNWs/TNAs had a layer of TiO₂ nanowires with a length of ~6 µm partially covering the TNAs. In addition, both TNAs and TNWs/TNAs had pure anatase phase TiO₂ with (101) and (112) dominant preferred orientations. Moreover, the TNAs and TNWs/TNAs effectively and rapidly degraded the antibiotic residues under UV-VIS irradiation at 120 mW/cm² and obtained over 95% removal at 20 min. Indeed, the photocatalytic reaction rate constants (k) were in the range of 0.14–0.36 min⁻¹ for TNAs, and 0.15–0.38 min⁻¹ for TNWs/TNAs. Noticeably, the k values of TNWs/TNAs were slightly higher than those of TNAs for LCM, DXC, OTC, SMZ, and SMX that could be attributed to the larger surface area of TNWs/TNAs than TNAs when TNWs/TNAs had an additional ~6μm TNWs top layer. Full article

(This article belongs to the Special Issue Recent Advances in TiO2 Photocatalysts)

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14 pages, 4848 KiB

Open AccessArticle

The Use of Tunable Optical Absorption Plasmonic Au and Ag Decorated TiO₂ Structures as Efficient Visible Light Photocatalysts

by Xiaohong Yang, Yan Wang, Lingtong Zhang, Haitao Fu, Peng He, Dezhi Han, Tom Lawson and Xizhong An

Catalysts 2020, 10(1), 139; https://doi.org/10.3390/catal10010139 - 20 Jan 2020

Cited by 38 | Viewed by 4472

Abstract

Exploring solar-excited heterogeneous photocatalysts by taking advantage of surface plasmon resonance (SPR) has drawn growing research attention. As it could help to pave the way for global sustainable development. The decoration of TiO₂ particles with noble metals possessing SPR effects is regarded [...] Read more.

Exploring solar-excited heterogeneous photocatalysts by taking advantage of surface plasmon resonance (SPR) has drawn growing research attention. As it could help to pave the way for global sustainable development. The decoration of TiO₂ particles with noble metals possessing SPR effects is regarded as one of the most effective solutions. The perfect match of the SPR absorption band with the spectrum of incident light is an essential factor for plasmonic enhancement. However, modifying with sole noble metal is often limited as it tunes wavelength of only several nanometers. To overcome this drawback, an alternative approach can be offered by decoration with more than one noble metal. For instance, Au-Ag co-decoration displays greatly adjustable, composition-dependent SPR agent over a broad range of the visible light spectrum (ca. from 415 to 525 nm). Hence Au-Ag complex is a remarkable candidate for tuning the photo adsorption of TiO₂ from UV to visible light. This study presents a novel and tailored method for the fabrication of Au-Ag co-modified TiO₂ particles, and how Au-Ag dependent SPR was applied as the visible light-responsive TiO₂ based photocatalysts in a simple but reliable way. The fabricated Au-Ag co-decorated TiO₂ (Au_xAg_(1−x)/TiO₂) was characterized and proved to own excellent stability and large specific surface area. The optimization of these particles against the wavelength of maximal solar light intensity was confirmed by photo degradation of methylene blue under visible light radiation. This work may provide further insight into the design of TiO₂-based composites with improved photocatalytic properties for environmental remediation and renewable energy utilization. Full article

(This article belongs to the Special Issue Recent Advances in TiO2 Photocatalysts)

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19 pages, 2552 KiB

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Solar Photocatalytic Degradation of Sulfamethoxazole by TiO₂ Modified with Noble Metals

by Ewa Borowska, João F. Gomes, Rui C. Martins, Rosa M. Quinta-Ferreira, Harald Horn and Marta Gmurek

Catalysts 2019, 9(6), 500; https://doi.org/10.3390/catal9060500 - 30 May 2019

Cited by 38 | Viewed by 5389

Abstract

Application of solar photocatalysis for water treatment is intensively studied. In this work, we investigated TiO₂ modified with platinum (Pt/TiO₂) and palladium (Pd/TiO₂) using sulfamethoxazole (SMX) as the model contaminant. We considered the following parameters: (i) level of [...] Read more.

Application of solar photocatalysis for water treatment is intensively studied. In this work, we investigated TiO₂ modified with platinum (Pt/TiO₂) and palladium (Pd/TiO₂) using sulfamethoxazole (SMX) as the model contaminant. We considered the following parameters: (i) level of TiO₂ modification with Pt/Pd, (ii) initial concentration of photocatalysts, (iii) geographic location where processes were conducted, and (iv) natural water matrix. The catalysts characterized by SEM, EDX, DRS, and XRD techniques showed successful deposition of Pd and Pt atoms on TiO₂ surface that enabled light absorption in the visible (Vis) range, and therefore caused efficient SMX removal in all tested conditions. A comparison of the rate constants of SMX degradation in various conditions revealed that modification with Pd gave better results than modification with Pt, which was explained by the better optical properties of Pd/TiO₂. The removal of SMX was higher with Pd/TiO₂ than with Pt/TiO₂, independent of the modification level. In the experiments with the same modification level, similar rate constants were achieved when four times the lower concentration of Pd/TiO₂ was used as compared with Pt/TiO₂. Formation of four SMX transformation products was confirmed, in which both amine groups are involved in photocatalytic oxidation. No toxic effect of post-reaction solutions towards Lepidium sativum was observed. Full article

(This article belongs to the Special Issue Recent Advances in TiO2 Photocatalysts)

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51 pages, 12744 KiB

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TiO₂-Graphene Quantum Dots Nanocomposites for Photocatalysis in Energy and Biomedical Applications

by Anuja Bokare, Sowbaranigha Chinnusamy and Folarin Erogbogbo

Catalysts 2021, 11(3), 319; https://doi.org/10.3390/catal11030319 - 28 Feb 2021

Cited by 49 | Viewed by 9862

Abstract

The focus of current research in material science has shifted from “less efficient” single-component nanomaterials to the superior-performance, next-generation, multifunctional nanocomposites. TiO₂ is a widely used benchmark photocatalyst with unique physicochemical properties. However, the large bandgap and massive recombination of photogenerated charge [...] Read more.

The focus of current research in material science has shifted from “less efficient” single-component nanomaterials to the superior-performance, next-generation, multifunctional nanocomposites. TiO₂ is a widely used benchmark photocatalyst with unique physicochemical properties. However, the large bandgap and massive recombination of photogenerated charge carriers limit its overall photocatalytic efficiency. When TiO₂ nanoparticles are modified with graphene quantum dots (GQDs), some significant improvements can be achieved in terms of (i) broadening the light absorption wavelengths, (ii) design of active reaction sites, and (iii) control of the electron-hole (e⁻-h⁺) recombination. Accordingly, TiO₂-GQDs nanocomposites exhibit promising multifunctionalities in a wide range of fields including, but not limited to, energy, biomedical aids, electronics, and flexible wearable sensors. This review presents some important aspects of TiO₂-GQDs nanocomposites as photocatalysts in energy and biomedical applications. These include: (1) structural formulations and synthesis methods of TiO₂-GQDs nanocomposites; (2) discourse about the mechanism behind the overall higher photoactivities of these nanocomposites; (3) various characterization techniques which can be used to judge the photocatalytic performance of these nanocomposites, and (4) the application of these nanocomposites in biomedical and energy conversion devices. Although some objectives have been achieved, new challenges still exist and hinder the widespread application of these nanocomposites. These challenges are briefly discussed in the Future Scope section of this review. Full article

(This article belongs to the Special Issue Recent Advances in TiO2 Photocatalysts)

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16 pages, 3013 KiB

Open AccessReview

Recent Advances in Synthesis and Applications of Carbon-Doped TiO₂ Nanomaterials

by Li Hua, Zhengliang Yin and Shunsheng Cao

Catalysts 2020, 10(12), 1431; https://doi.org/10.3390/catal10121431 - 8 Dec 2020

Cited by 59 | Viewed by 5861

Abstract

TiO₂ has been widely used as a photocatalyst and an electrode material toward the photodegradation of organic pollutants and electrochemical applications, respectively. However, the properties of TiO₂ are not enough up to meet practical needs because of its intrinsic disadvantages such [...] Read more.

TiO₂ has been widely used as a photocatalyst and an electrode material toward the photodegradation of organic pollutants and electrochemical applications, respectively. However, the properties of TiO₂ are not enough up to meet practical needs because of its intrinsic disadvantages such as a wide bandgap and low conductivity. Incorporation of carbon into the TiO₂ lattice is a promising tool to overcome these limitations because carbon has metal-like conductivity, high separation efficiency of photogenerated electron/hole pairs, and strong visible-light absorption. This review would describe and discuss a variety of strategies to develop carbon-doped TiO₂ with enhanced photoelectrochemical performances in environmental, energy, and catalytic fields. Emphasis is given to highlight current techniques and recent progress in C-doped TiO₂-based materials. Meanwhile, how to tackle the challenges we are currently facing is also discussed. This understanding will allow the process to continue to evolve and provide facile and feasible techniques for the design and development of carbon-doped TiO₂ materials. Full article

(This article belongs to the Special Issue Recent Advances in TiO2 Photocatalysts)

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30 pages, 6923 KiB

Open AccessReview

Recent Developments of Advanced Ti³⁺-Self-Doped TiO₂ for Efficient Visible-Light-Driven Photocatalysis

by Siyoung Na, Sohyeon Seo and Hyoyoung Lee

Catalysts 2020, 10(6), 679; https://doi.org/10.3390/catal10060679 - 17 Jun 2020

Cited by 37 | Viewed by 6002

Abstract

Research into the development of efficient semiconductor photocatalytic materials is a promising approach to solving environmental and energy problems worldwide. Among these materials, TiO₂ photocatalysts are one of the most commonly used due to their efficient photoactivity, high stability, low cost and [...] Read more.

Research into the development of efficient semiconductor photocatalytic materials is a promising approach to solving environmental and energy problems worldwide. Among these materials, TiO₂ photocatalysts are one of the most commonly used due to their efficient photoactivity, high stability, low cost and environmental friendliness. However, since the UV content of sunlight is less than 5%, the development of visible light-activated TiO₂-based photocatalysts is essential to increase the solar energy efficiency. Here, we review recent works on advanced visible light-activated Ti³⁺-self-doped TiO₂ (Ti³⁺–TiO₂) photocatalysts with improved electronic band structures for efficient charge separation. We analyze the different methods used to produce Ti³⁺–TiO₂ photocatalysts, where Ti³⁺ with a high oxygen defect density can be used for energy production from visible light. We categorize advanced modifications in electronic states of Ti³⁺–TiO₂ by improving their photocatalytic activity. Ti³⁺–TiO₂ photocatalysts with large charge separation and low recombination of photogenerated electrons and holes can be practically applied for energy conversion and advanced oxidation processes in natural environments and deserve significant attention. Full article

(This article belongs to the Special Issue Recent Advances in TiO2 Photocatalysts)

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