Research

13 pages, 3764 KiB

Open AccessFeature PaperArticle

Advanced Removal of Dyes with Tuning Carbon/TiO₂ Composite Properties

by Halyna Bodnar Yankovych, Coset Abreu-Jaureguí, Judit Farrando-Perez, Inna Melnyk, Miroslava Václavíková and Joaquín Silvestre-Albero

Nanomaterials 2024, 14(3), 309; https://doi.org/10.3390/nano14030309 - 03 Feb 2024

Viewed by 826

Abstract

This study evaluates the removal of several dyes with different charge properties, i.e., anionic (Acid Red 88), cationic (Basic Red 13), and neutral (Basic Red 5) using transition metal-doped TiO₂ supported on a high-surface-area activated carbon. Experimental results confirm the successful deposition [...] Read more.

This study evaluates the removal of several dyes with different charge properties, i.e., anionic (Acid Red 88), cationic (Basic Red 13), and neutral (Basic Red 5) using transition metal-doped TiO₂ supported on a high-surface-area activated carbon. Experimental results confirm the successful deposition of TiO₂ and the derivatives (Zr-, Cu-, and Ce-doped samples) on the surface of the activated carbon material and the development of extended heterojunctions with improved electronic properties. Incorporating a small percentage of dopants significantly improves the adsorption properties of the composites towards the three dyes evaluated, preferentially for sample AC/TiO₂_Zr. Similarly, the photodegradation efficiency highly depends on the nature of the composite evaluated and the characteristics of the dye. Sample AC/TiO₂_Zr demonstrates the best overall removal efficiency for Acid Red 88 and Basic Red 5—83% and 63%, respectively. This promising performance must simultaneously be attributed to a dual mechanism, i.e., adsorption and photodegradation. Notably, the AC/TiO₂_Ce outperformed the other catalysts in eliminating Basic Red 13 (74%/6 h). A possible Acid Red 88 degradation mechanism using AC/TiO₂_Zr was proposed. This study shows that the removal efficiency of AC/TiO₂ composites strongly depends on both the material and pollutant. Full article

(This article belongs to the Special Issue Applications of Nanomaterials for Electrocatalysis, Photocatalysis, Photoelectrochemical Solar Cells and Toxicity)

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17 pages, 1962 KiB

Open AccessArticle

Removal of Diclofenac and Heavy Metal Ions from Aqueous Media Using Composite Sorbents in Dynamic Conditions

by Daniela Fighir, Carmen Paduraru, Ramona Ciobanu, Florin Bucatariu, Oana Plavan, Andreea Gherghel, George Barjoveanu, Marcela Mihai and Carmen Teodosiu

Nanomaterials 2024, 14(1), 33; https://doi.org/10.3390/nano14010033 - 21 Dec 2023

Viewed by 747

Abstract

Pharmaceuticals and heavy metals pose significant risks to human health and aquatic ecosystems, necessitating their removal from water and wastewater. A promising alternative for this purpose involves their removal by adsorption on composite sorbents prepared using a conventional layer-by-layer (LbL) method or an [...] Read more.

Pharmaceuticals and heavy metals pose significant risks to human health and aquatic ecosystems, necessitating their removal from water and wastewater. A promising alternative for this purpose involves their removal by adsorption on composite sorbents prepared using a conventional layer-by-layer (LbL) method or an innovative coacervate direct deposition approach. In this study, four novel composite materials based on a silica core (IS) and a polyelectrolyte coacervate shell were used for the investigation of dynamic adsorption of three heavy metals (lead, nickel and cadmium) and an organic drug model (diclofenac sodium salt, DCF-Na). The four types of composite sorbents were tested for the first time in dynamic conditions (columns with continuous flow), and the column conditions were similar to those used in wastewater treatment plants. The influence of the polyanion nature (poly(acrylic acid) (PAA) vs. poly(sodium methacrylate) (PMAA)), maintaining a constant poly(ethyleneimine) (PEI), and the cross-linking degree (r = 0.1 and r = 1.0) of PEI chains on the immobilization of these pollutants (inorganic vs. organic) on the same type of composite was also studied. The experiments involved both single- and multi-component aqueous solutions. The kinetics of the dynamic adsorption process were examined using two non-linear models: the Thomas and Yoon–Nelson models. The tested sorbents demonstrated good adsorption capacities with affinities for the metal ions in the following order: Pb²⁺ > Cd²⁺ > Ni²⁺. An increase in the initial diclofenac sodium concentration led to an enhanced adsorption capacity of the IS/(PEI-PAA)_c-r1 sorbent. The calculated sorption capacities were in good agreement with the adsorption capacity predicted by the Thomas and Yoon–Nelson models. The substantial affinity observed between DCF-Na and a column containing composite microparticles saturated with heavy metal ions was explained. Full article

(This article belongs to the Special Issue Applications of Nanomaterials for Electrocatalysis, Photocatalysis, Photoelectrochemical Solar Cells and Toxicity)

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14 pages, 4156 KiB

Open AccessArticle

Experimental and Theoretical Investigation of Gadolinium Oxyhydride (GdHO) Thin Films: Optical, Photocatalytic, and Electronic Properties

by Kasi Vinoth Kumar, Luminita Andronic, Elbruz Murat Baba, Dargie Deribew, Jeyanthinath Mayandi, Ellen Moons and Smagul Zh. Karazhanov

Nanomaterials 2023, 13(24), 3093; https://doi.org/10.3390/nano13243093 - 07 Dec 2023

Cited by 1 | Viewed by 896

Abstract

Oxyhydrides of rare-earth metals (REMOHs) exhibit notable photochromic behaviors. Among these, yttrium oxyhydride (YHO) stands out for its impressive transparency and swift UV-responsive color change, positioning it as an optimal material for self-cleaning window applications. Although semiconductor photocatalysis holds potential solutions for critical [...] Read more.

Oxyhydrides of rare-earth metals (REMOHs) exhibit notable photochromic behaviors. Among these, yttrium oxyhydride (YHO) stands out for its impressive transparency and swift UV-responsive color change, positioning it as an optimal material for self-cleaning window applications. Although semiconductor photocatalysis holds potential solutions for critical environmental issues, optimizing the photocatalytic efficacy of photochromic substances has not been adequately addressed. This research advances the study of REMOHs, focusing on the properties of gadolinium oxyhydride (GdHO) both theoretically and experimentally. The electronic and structural characteristics of GdHO, vital for ceramic technology, are thoroughly examined. Explicitly determined work functions for GdH₂, GdHO, and Gd₂O₃ stand at 3.4 eV, 3.0 eV, and 4.3 eV, respectively. Bader charge analysis showcases GdHO’s intricate bonding attributes, whereas its electron localization function majorly presents an ionic nature. The charge neutrality level is situated about 0.33 eV below the top valence band, highlighting these materials’ inclination for acceptor-dominant electrical conductivity. Remarkably, this research unveils GdHO films’ photocatalytic capabilities for the first time. Even with their restricted surface due to thinness, these films follow the Langmuir–Hinshelwood degradation kinetics, ensuring total degradation of methylene blue in a day. It was observed that GdHO’s work function diminishes with reduced deposition pressure, and UV exposure further decreases it by 0.2 eV—a change that reverts post-UV exposure. The persistent stability of GdHO films, hinting at feasible recyclability, enhances their potential efficiency, underlining their viability in practical applications. Overall, this study accentuates GdHO’s pivotal role in electronics and photocatalysis, representing a landmark advancement in the domain. Full article

(This article belongs to the Special Issue Applications of Nanomaterials for Electrocatalysis, Photocatalysis, Photoelectrochemical Solar Cells and Toxicity)

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14 pages, 6008 KiB

Open AccessArticle

Bi/Mn-Doped BiOCl Nanosheets Self-Assembled Microspheres toward Optimized Photocatalytic Performance

by Shijie Wang, Dongxue Song, Lijun Liao, Bo Wang, Zhenzi Li, Mingxia Li and Wei Zhou

Nanomaterials 2023, 13(17), 2408; https://doi.org/10.3390/nano13172408 - 25 Aug 2023

Viewed by 899

Abstract

Doping engineering of metallic elements is of significant importance in photocatalysis, especially in the transition element range where metals possess empty ‘d’ orbitals that readily absorb electrons and increase carrier concentration. The doping of Mn ions produces dipole interactions that change the local [...] Read more.

Doping engineering of metallic elements is of significant importance in photocatalysis, especially in the transition element range where metals possess empty ‘d’ orbitals that readily absorb electrons and increase carrier concentration. The doping of Mn ions produces dipole interactions that change the local structure of BiOCl, thus increasing the specific surface area of BiOCl and the number of mesoporous distributions, and providing a broader platform and richer surface active sites for catalytic reactions. The combination of Mn doping and metal Bi reduces the forbidden bandwidth of BiOCl, thereby increasing the absorption in the light region and strengthening the photocatalytic ability of BiOCl. The degradation of norfloxacin by Bi/Mn-doped BiOCl can reach 86.5% within 10 min. The synergistic effect of Mn doping and Bi metal can change the internal energy level and increase light absorption simultaneously. The photocatalytic system created by such a dual-technology combination has promising applications in environmental remediation. Full article

(This article belongs to the Special Issue Applications of Nanomaterials for Electrocatalysis, Photocatalysis, Photoelectrochemical Solar Cells and Toxicity)

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15 pages, 3708 KiB

Open AccessEditor’s ChoiceArticle

Construction of 2D/2D Mesoporous WO₃/CeO₂ Laminated Heterojunctions for Optimized Photocatalytic Performance

by Wenjie Wang, Decai Yang, Yifan Mou, Lijun Liao, Shijie Wang, Liping Guo, Xuepeng Wang, Zhenzi Li and Wei Zhou

Nanomaterials 2023, 13(11), 1798; https://doi.org/10.3390/nano13111798 - 04 Jun 2023

Cited by 2 | Viewed by 1295

Abstract

Photocatalytic elimination of antibiotics from the environment and drinking water is of great significance for human health. However, the efficiency of photoremoval of antibiotics such as tetracycline is severely limited by the prompt recombination of electron holes and slow charge migration efficacy. Fabrication [...] Read more.

Photocatalytic elimination of antibiotics from the environment and drinking water is of great significance for human health. However, the efficiency of photoremoval of antibiotics such as tetracycline is severely limited by the prompt recombination of electron holes and slow charge migration efficacy. Fabrication of low-dimensional heterojunction composites is an efficient method for shortening charge carrier migration distance and enhancing charge transfer efficiency. Herein, 2D/2D mesoporous WO₃/CeO₂ laminated Z-scheme heterojunctions were successfully prepared using a two-step hydrothermal process. The mesoporous structure of the composites was proved by nitrogen sorption isotherms, in which sorption-desorption hysteresis was observed. The intimate contact and charge transfer mechanism between WO₃ nanoplates and CeO₂ nanosheets was investigated using high-resolution transmission electron microscopy and X-ray photoelectron spectroscopy measurements, respectively. Photocatalytic tetracycline degradation efficiency was noticeably promoted by the formation of 2D/2D laminated heterojunctions. The improved photocatalytic activity could be attributed to the formation of Z-scheme laminated heterostructure and 2D morphology favoring spatial charge separation, confirmed by various characterizations. The optimized 5WO₃/CeO₂ (5 wt.% WO₃) composites can degrade more than 99% of tetracycline in 80 min, achieving a peak TC photodegradation efficiency of 0.0482 min⁻¹, which is approximately 3.4 times that of pristine CeO₂. A Z-scheme mechanism is proposed for photocatalytic tetracycline by from WO₃/CeO₂ Z-scheme laminated heterojunctions based on the experimental results. Full article

(This article belongs to the Special Issue Applications of Nanomaterials for Electrocatalysis, Photocatalysis, Photoelectrochemical Solar Cells and Toxicity)

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17 pages, 4408 KiB

Open AccessArticle

Oxygen Vacancy Mediated Band-Gap Engineering via B-Doping for Enhancing Z-Scheme A-TiO₂/R-TiO₂ Heterojunction Photocatalytic Performance

by Changqing Liu, Chenggang Xu, Wanting Wang, Long Chen, Xu Li and Yuanting Wu

Nanomaterials 2023, 13(5), 794; https://doi.org/10.3390/nano13050794 - 21 Feb 2023

Cited by 6 | Viewed by 1529

Abstract

Fabrication of Z-scheme heterojunction photocatalysts is an ideal strategy for solving environmental problems by providing inexhaustible solar energy. A direct Z-scheme anatase TiO₂/rutile TiO₂ heterojunction photocatalyst was prepared using a facile B-doping strategy. The band structure and oxygen-vacancy content can [...] Read more.

Fabrication of Z-scheme heterojunction photocatalysts is an ideal strategy for solving environmental problems by providing inexhaustible solar energy. A direct Z-scheme anatase TiO₂/rutile TiO₂ heterojunction photocatalyst was prepared using a facile B-doping strategy. The band structure and oxygen-vacancy content can be successfully tailored by controlling the amount of B-dopant. The photocatalytic performance was enhanced via the Z-scheme transfer path formed between the B doped anatase-TiO₂ and rutile-TiO₂, optimized band structure with markedly positively shifted band potentials, and the synergistically-mediated oxygen vacancy contents. Moreover, the optimization study indicated that 10% B-doping with the R-TiO₂ to A-TiO₂ weight ratio of 0.04 could achieve the highest photocatalytic performance. This work may provide an effective approach to synthesize nonmetal-doped semiconductor photocatalysts with tunable-energy structures and promote the efficiency of charge separation. Full article

(This article belongs to the Special Issue Applications of Nanomaterials for Electrocatalysis, Photocatalysis, Photoelectrochemical Solar Cells and Toxicity)

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15 pages, 3663 KiB

Open AccessArticle

Effect of Iodide-Based Organic Salts and Ionic Liquid Additives in Dye-Sensitized Solar Cell Performance

by João Sarrato, Ana Lucia Pinto, Hugo Cruz, Noémi Jordão, Gabriela Malta, Paula S. Branco, J. Carlos Lima and Luis C. Branco

Nanomaterials 2022, 12(17), 2988; https://doi.org/10.3390/nano12172988 - 29 Aug 2022

Cited by 3 | Viewed by 1338

Abstract

The use of ionic liquid and organic salts as additives for electrolyte systems in dye-sensitized solar cells have been widely described in recent years. The tunability of their physical-chemical properties according to the cation–anion selection contributes toward their high efficiencies. For this purpose, [...] Read more.

The use of ionic liquid and organic salts as additives for electrolyte systems in dye-sensitized solar cells have been widely described in recent years. The tunability of their physical-chemical properties according to the cation–anion selection contributes toward their high efficiencies. For this purpose, several iodide-based organic salts including imidazolium, picolinium, guanidinium and alkylammonium cations were tested using acetonitrile/valeronitrile electrolytes and their photovoltaic parameters were compared. A best efficiency of 4.48% (4.15% for the reference) was found for 1-ethyl-2,3-dimethylimidazolium iodide ([C2DMIM]I) containing electrolyte, reaffirming the effectiveness of these additives. 4-tertbutylpyridine was included into the formulation to further improve the performance while determining which iodide salts demonstrate the highest synergy with this additive. [C2DMIM]I once again proved to be the superior additive, achieving an efficiency of 6.48% (6% for the reference). Electrochemical impedance spectroscopy was employed to elucidate the effects of the various additives, demonstrating the relevance of the counter electrode resistance on device performance. Finally, several computational descriptors for the cationic structures were calculated and correlated with the photovoltaic and resistance parameters, showing that properties related to polarity, namely relative positive charge, molecular polarizability and partition coefficient are in good agreement with the counter-electrode resistance. Full article

(This article belongs to the Special Issue Applications of Nanomaterials for Electrocatalysis, Photocatalysis, Photoelectrochemical Solar Cells and Toxicity)

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10 pages, 2399 KiB

Open AccessArticle

An Electrochromic Ag-Decorated WO_3−x Film with Adjustable Defect States for Electrochemical Surface-Enhanced Raman Spectroscopy

by Siqi Qu, Jing Guan, Dongqi Cai, Qianshuo Wang, Xiuyun Wang, Wei Song and Wei Ji

Nanomaterials 2022, 12(10), 1637; https://doi.org/10.3390/nano12101637 - 11 May 2022

Cited by 3 | Viewed by 1645

Abstract

Electrochemical surface-enhanced Raman scattering (EC-SERS) spectroscopy is an ultrasensitive spectro-electrochemistry technique that provides mechanistic and dynamic information on electrochemical interfaces at the molecular level. However, the plasmon-mediated photocatalysis hinders the intrinsic electrochemical behavior of molecules at electrochemical interfaces. This work aimed to develop [...] Read more.

Electrochemical surface-enhanced Raman scattering (EC-SERS) spectroscopy is an ultrasensitive spectro-electrochemistry technique that provides mechanistic and dynamic information on electrochemical interfaces at the molecular level. However, the plasmon-mediated photocatalysis hinders the intrinsic electrochemical behavior of molecules at electrochemical interfaces. This work aimed to develop a facile method for constructing a reliable EC-SERS substrate that can be used to study the molecular dynamics at electrochemical interfaces. Herein, a novel Ag-WO_3−x electrochromic heterostructure was synthesized for EC-SERS. Especially, the use of electrochromic WO_3−x film suppresses the influence of hot-electrons-induced catalysis while offering a reliable SERS effect. Based on this finding, the real electrochemical behavior of p-aminothiophenol (PATP) on Ag nanoparticles (NPs) surface was revealed for the first time. We are confident that metal-semiconductor electrochromic heterostructures could be developed into reliable substrates for EC-SERS analysis. Furthermore, the results obtained in this work provide new insights not only into the chemical mechanism of SERS, but also into the hot-electron transfer mechanism in metal-semiconductor heterostructures. Full article

(This article belongs to the Special Issue Applications of Nanomaterials for Electrocatalysis, Photocatalysis, Photoelectrochemical Solar Cells and Toxicity)

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