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3 pages, 189 KiB

Open AccessEditorial

Special Issue: Photocatalytic Materials for Environment Treatment and Energy Production

by Luminita Isac

Materials 2022, 15(10), 3631; https://doi.org/10.3390/ma15103631 - 19 May 2022

Cited by 1 | Viewed by 1037

Abstract

Nowadays, given the major problems facing humanity, the increasing environmental pollution and the need for sustainable and cheap energy sources represent important research issues [...] Full article

(This article belongs to the Special Issue Photocatalytic Materials for Environment Treatment and Energy Production)

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15 pages, 2717 KiB

Open AccessArticle

Visible-Light-Driven AO7 Photocatalytic Degradation and Toxicity Removal at Bi-Doped SrTiO₃

by Maria João Nunes, Ana Lopes, Maria José Pacheco and Lurdes Ciríaco

Materials 2022, 15(7), 2465; https://doi.org/10.3390/ma15072465 - 27 Mar 2022

Cited by 11 | Viewed by 1945

Abstract

In this study, Bi-doped SrTiO₃ perovskites (Sr_1−xBi_xTiO₃, x = 0, 0.03, 0.05, 0.07 and 0.1) were synthesized using the solid-state method, characterized, and tested as photocatalysts in the degradation of the azo dye acid orange 7 [...] Read more.

In this study, Bi-doped SrTiO₃ perovskites (Sr_1−xBi_xTiO₃, x = 0, 0.03, 0.05, 0.07 and 0.1) were synthesized using the solid-state method, characterized, and tested as photocatalysts in the degradation of the azo dye acid orange 7 (AO7) under visible light. The perovskites were successfully synthesized, and XRD data showed a predominant, well-crystallized phase, belonging to the cubic perovskite symmetry. For the doped samples, a minority phase, identified as bismuth titanate, was detected. All doped samples exhibited improved photocatalytic activity under visible light, on the degradation of AO7 (10 mg L⁻¹), when compared with the undoped SrTiO₃, with an increase in relative Abs_{484 nm} decay from 3.7% to ≥67.8% after 1 h, for a powder suspension of 0.2 g L⁻¹. The best photocatalytic activity was exhibited by the Sr_0.95Bi_0.05TiO₃ perovskite. Reusability studies showed no significant loss in photocatalytic activity under visible light. The final solutions showed no toxicity towards D. magna, proving the efficiency of Sr_0.95Bi_0.05TiO₃ as a visible-light-driven photocatalyst to degrade both the AO7 dye as well as its toxic by-products. A degradation mechanism is proposed. Full article

(This article belongs to the Special Issue Photocatalytic Materials for Environment Treatment and Energy Production)

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11 pages, 3510 KiB

Open AccessArticle

Determination of Band Structure of Naturally Occurring Goethite with Al Substitution: A Case Study of Zhushan Iron Zone

by Yan Shao, Guofeng Hu, Zihao Liu, Xiaoming Xu, Mengqi Zhang, Cong Ding and Yan Li

Materials 2022, 15(4), 1465; https://doi.org/10.3390/ma15041465 - 16 Feb 2022

Cited by 7 | Viewed by 2242

Abstract

The photocatalytic property of Fe oxide minerals has long been considered to play an important role in shaping modern terrestrial environments. However, due to the complexity of natural settings, a precise determination of the band structure of natural goethite has not been achieved. [...] Read more.

The photocatalytic property of Fe oxide minerals has long been considered to play an important role in shaping modern terrestrial environments. However, due to the complexity of natural settings, a precise determination of the band structure of natural goethite has not been achieved. In this work, the mineralogical characteristics of natural goethite samples obtained from Zhushan, China, were systematically studied through X-ray diffraction, transmission electron microscopy, X-ray energy dispersive spectroscopy, and X-ray fluorescence spectroscopy. Afterward, the band structure for both natural and synthetic goethite samples was determined by synchrotron-based X-ray absorption and emission spectra and photoelectron spectroscopy. The band gap of natural goethite (2.25 eV) was narrower than that of its synthetic counterpart (2.55 eV), and the valence band position of natural goethite was slightly lifted (−5.06 eV) compared to that of synthetic goethite (−5.38 eV). Al doping in natural goethite crystal, as revealed by the mineralogical tests, was the main reason that contributed to this difference. The theoretical calculation showed the narrowed band gap was caused by the contribution of Al-2p orbits at the top of the valence band. Therefore, free electrons can be created under light irradiation with a shorter wavelength. The experiments showed that natural goethite can photo-catalytically degrade methyl orange, and the degradation efficiency was better (47.5%) than that of the synthetic goethite group (31.5%). This study, for the first time, revealed the band structure and confirmed the photocatalytic properties of natural goethite, which should play an important role in surface substance evolution and elemental cycling. Full article

(This article belongs to the Special Issue Photocatalytic Materials for Environment Treatment and Energy Production)

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16 pages, 2423 KiB

Open AccessArticle

Reductive Modification of Carbon Nitride Structure by Metals—The Influence on Structure and Photocatalytic Hydrogen Evolution

by Emilia Alwin, Robert Wojcieszak, Kamila Kočí, Miroslava Edelmannová, Michał Zieliński, Agata Suchora, Tomasz Pędziński and Mariusz Pietrowski

Materials 2022, 15(3), 710; https://doi.org/10.3390/ma15030710 - 18 Jan 2022

Cited by 9 | Viewed by 1752

Abstract

Pt, Ru, and Ir were introduced onto the surface of graphitic carbon nitride (g-C₃N₄) using the wet impregnation method. A reduction of these photocatalysts with hydrogen causes several changes, such as a significant increase in the specific surface area, [...] Read more.

Pt, Ru, and Ir were introduced onto the surface of graphitic carbon nitride (g-C₃N₄) using the wet impregnation method. A reduction of these photocatalysts with hydrogen causes several changes, such as a significant increase in the specific surface area, a C/N atomic ratio, a number of defects in the crystalline structure of g-C₃N₄, and the contribution of nitrogen bound to the amino and imino groups. According to the X-ray photoelectron spectroscopy results, a transition layer is formed at the g-C₃N₄/metal nanoparticle interphase, which contains metal at a positive degree of oxidation bonded to nitrogen. These structural changes significantly enhanced the photocatalytic activity in the production of hydrogen through the water-splitting reaction. The activity of the platinum photocatalyst was 24 times greater than that of pristine g-C₃N₄. Moreover, the enhanced activity was attributed to significantly better separation of photogenerated electron–hole pairs on metal nanoparticles and structural distortions of g-C₃N₄. Full article

(This article belongs to the Special Issue Photocatalytic Materials for Environment Treatment and Energy Production)

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11 pages, 3160 KiB

Open AccessArticle

Enhanced Photodegradation of p-Nitrobenzoic Acid by Binary Mixtures with Ba²⁺/TiO₂ and MCM-41

by Xianyuan Fan, Hong Liu, Weikun Song and Chia-Yuan Chang

Materials 2021, 14(9), 2404; https://doi.org/10.3390/ma14092404 - 5 May 2021

Cited by 3 | Viewed by 1646

Abstract

A novel Ba(II)/TiO₂–MCM-41 composite was synthesized using binary mixtures with Ba²⁺/TiO₂ and MCM-41, and Ba²⁺ as a doping ion of TiO₂. The specific surface area and pore structure characterizations confirm that a mesoporous structure with [...] Read more.

A novel Ba(II)/TiO₂–MCM-41 composite was synthesized using binary mixtures with Ba²⁺/TiO₂ and MCM-41, and Ba²⁺ as a doping ion of TiO₂. The specific surface area and pore structure characterizations confirm that a mesoporous structure with a surface area of 341.2 m²/g and a narrow pore size distribution ranging from 2 to 4 nm was achieved using Ba(II)/TiO₂–MCM-41. Ba(II)/TiO₂ particles were synthesized into 10–15 nm particles and were well dispersed onto MCM-41. The diffraction peaks in the XRD patterns of TiO₂–MCM-41 and Ba(II)/TiO₂–MCM-41 were all attributed to anatase TiO₂. By taking advantage of MCM-41 and Ba²⁺, the photocatalytic performance of Ba(II)/TiO₂–MCM-41 was remarkably enhanced by suppressing its rutile phase, by lowering the band gap energy, and by facilitating the dispersion of TiO₂. Therefore, the photodegradation efficiencies of p-nitrobenzoic acid (4 × 10⁻⁴ mol/L) by various photocatalysts (60 min) under UV light irradiation are arranged in the following order: Ba(II)/TiO₂–MCM-41 (91.7%) > P25 (86.3%) > TiO₂–MCM-41 (80.6%) > Ba(II)/TiO₂ (55.7%) > TiO₂ (53.9%). The Ba(II)/TiO₂–MCM-41 composite was reused for five cycles and maintained a high catalytic activity (73%). Full article

(This article belongs to the Special Issue Photocatalytic Materials for Environment Treatment and Energy Production)

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14 pages, 5243 KiB

Open AccessArticle

Tuned S-Scheme Cu₂S_TiO₂_WO₃ Heterostructure Photocatalyst toward S-Metolachlor (S-MCh) Herbicide Removal

by Alexandru Enesca and Luminita Isac

Materials 2021, 14(9), 2231; https://doi.org/10.3390/ma14092231 - 26 Apr 2021

Cited by 11 | Viewed by 1591

Abstract

A dual S-scheme Cu₂S_TiO₂_WO₃ heterostructure was constructed by sol–gel method using a two-step procedure. Due to the synthesis parameters and annealing treatment the heterostructure is characterized by sulfur deficit and oxygen excess allowing the passivation of oxygen vacancies. [...] Read more.

A dual S-scheme Cu₂S_TiO₂_WO₃ heterostructure was constructed by sol–gel method using a two-step procedure. Due to the synthesis parameters and annealing treatment the heterostructure is characterized by sulfur deficit and oxygen excess allowing the passivation of oxygen vacancies. The photocatalytic activity was evaluated under UV and UV–Vis irradiation scenarios using S-MCh as reference pollutant. The heterostructure is composed on orthorhombic Cu₂S, anatase TiO₂ and monoclinic WO₃ with crystallite sizes varying from 65.2 Å for Cu₂S to 97.1 Å for WO₃. The heterostructure exhibit a dense morphology with pellets and particle-like morphology closely combined in a relatively compact assembly. The surface elemental composition indicate that the heterostructure maintain a similar atomic ratio as established during the synthesis with a slight sulfur deficit due to the annealing treatments. The results indicate that the three-component heterostructure have higher photocatalytic efficiency (61%) comparing with two-component heterostructure or bare components. Moreover, Cu₂S_TiO₂_WO₃ exhibit a superior constant rate (0.114 s⁻¹) due to the high concentration of photogenerated charge carriers, efficient charge separation and migration. Full article

(This article belongs to the Special Issue Photocatalytic Materials for Environment Treatment and Energy Production)

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13 pages, 5052 KiB

Open AccessArticle

Enhanced Photocatalytic Activity of Spherical Nd³⁺ Substituted ZnFe₂O₄ Nanoparticles

by Loan T. T. Nguyen, Hang T. T. Nguyen, Thieng H. Le, Lan T. H. Nguyen, Hai Q. Nguyen, Thanh T. H. Pham, Nguyen D. Bui, Ngan T. K. Tran, Duyen Thi Cam Nguyen, Tan Van Lam and Thuan Van Tran

Materials 2021, 14(8), 2054; https://doi.org/10.3390/ma14082054 - 19 Apr 2021

Cited by 26 | Viewed by 2500

Abstract

In this study, nanocrystalline ZnNd_xFe_2−xO₄ ferrites with x = 0.0, 0.01, 0.03 and 0.05 were fabricated and used as a catalyst for dye removal potential. The effect of Nd³⁺ ions substitution on the structural, optical and photo-Fenton [...] Read more.

In this study, nanocrystalline ZnNd_xFe_2−xO₄ ferrites with x = 0.0, 0.01, 0.03 and 0.05 were fabricated and used as a catalyst for dye removal potential. The effect of Nd³⁺ ions substitution on the structural, optical and photo-Fenton activity of ZnNd_xFe_2−xO₄ has been investigated. The addition of Nd³⁺ ions caused a decrease in the grain size of ferrites, the reduction of the optical bandgap energies and thus could be well exploited for the catalytic study. The photocatalytic activity of the ferrite samples was evaluated by the degradation of Rhodamine B (RhB) in the presence of H₂O₂ under visible light radiation. The results indicated that the ZnNd_xFe_2−xO₄ samples exhibited higher removal efficiencies than the pure ZnFe₂O₄ ferrites. The highest degradation efficiency was 98.00%, attained after 210 min using the ZnNd_0.03Fe_1.97O₄ sample. The enhanced photocatalytic activity of the ZnFe₂O₄ doped with Nd³⁺ is explained due to the efficient separation mechanism of photoinduced electron and holes. The effect of various factors (H₂O₂ oxidant concentration and catalyst loading) on the degradation of RhB dye was clarified. Full article

(This article belongs to the Special Issue Photocatalytic Materials for Environment Treatment and Energy Production)

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13 pages, 2001 KiB

Open AccessArticle

Comparison of Graphitic Carbon Nitrides Synthetized from Melamine and Melamine-Cyanurate Complex: Characterization and Photocatalytic Decomposition of Ofloxacin and Ampicillin

by Petr Praus, Aneta Smýkalová and Kryštof Foniok

Materials 2021, 14(8), 1967; https://doi.org/10.3390/ma14081967 - 14 Apr 2021

Cited by 7 | Viewed by 2340

Abstract

Graphitic carbon nitride (g-C₃N₄, hereafter abbreviated as CN) was prepared by the heating of melamine (CN-M) and melamine-cyanurate complex (CN-MCA), respectively, in air at 550 °C for 4 h. The specific surface area (SSA) of CN-M and CN-MCA was [...] Read more.

Graphitic carbon nitride (g-C₃N₄, hereafter abbreviated as CN) was prepared by the heating of melamine (CN-M) and melamine-cyanurate complex (CN-MCA), respectively, in air at 550 °C for 4 h. The specific surface area (SSA) of CN-M and CN-MCA was 12 m² g⁻¹ and 225 m²g⁻¹ and the content of oxygen was 0.62 wt.% and 1.88 wt.%, respectively. The band gap energy (E_g) of CN-M was 2.64 eV and E_g of CN-MCA was 2.73 eV. The photocatalytic activity of the CN materials was tested by means of the decomposition of antibiotics ofloxacin and ampicillin under LED irradiation of 420 nm. The activity of CN-MCA was higher due to its high SSA, which was determined based on the physisorption of nitrogen. Ofloxacin was decomposed more efficiently than ampicillin in the presence of both photocatalysts. Full article

(This article belongs to the Special Issue Photocatalytic Materials for Environment Treatment and Energy Production)

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14 pages, 6024 KiB

Open AccessArticle

The Influence of Light Irradiation on the Photocatalytic Degradation of Organic Pollutants

by Alexandru Enesca and Luminita Isac

Materials 2020, 13(11), 2494; https://doi.org/10.3390/ma13112494 - 29 May 2020

Cited by 15 | Viewed by 2262

Abstract

The design of a photocatalytic process must consider intrinsic and extrinsic parameters affecting its overall efficiency. This study aims to outline the importance of balancing several factors, such as radiation source, total irradiance, photon flux, catalyst substrate, and pollutant type in order to [...] Read more.

The design of a photocatalytic process must consider intrinsic and extrinsic parameters affecting its overall efficiency. This study aims to outline the importance of balancing several factors, such as radiation source, total irradiance, photon flux, catalyst substrate, and pollutant type in order to optimize the photocatalytic efficiency. Titanium oxide was deposed by the doctor blade technique on three substrates (microscopic glass (G), flour-doped tin oxide (FTO), and aluminum (Al)), and the photocatalytic properties of the samples were tested on two pollutants (tartrazine (Tr) and acetamiprid (Apd)). Seven irradiation scenarios were tested using different ratios of UV-A, UV-B + C, and Vis radiations. The results indicated that the presence of a conductive substrate and a suitable ratio of UV-A and Vis radiations could increase the photocatalytic efficiency of the samples. Higher efficiencies were obtained for the sample Ti_FTO (58.3% for Tr and 70.8% for Apd) and the sample Ti_Al (63.8% for Tr and 82.3% for Apd) using a mixture of three UV-A and one Vis sources (13.5 W/m² and 41.85 μmol/(m²·s)). A kinetic evaluation revealed two different mechanisms of reaction: (a) a one-interval mechanism related to Apd removal by Ti_FTO, Ti_Al (scenarios 1, 4, 5, and 7), and Ti_G samples (scenario 7) and (b) a two-interval mechanism in all other cases. Full article

(This article belongs to the Special Issue Photocatalytic Materials for Environment Treatment and Energy Production)

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