Applications of Nanomaterials for Electrocatalysis, Photocatalysis, Photoelectrochemical Solar Cells and Toxicity

A special issue of Nanomaterials (ISSN 2079-4991). This special issue belongs to the section "Energy and Catalysis".

Deadline for manuscript submissions: closed (20 May 2024) | Viewed by 10451

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Solar Energy Department, Institute for Energy Technology, P.O Box 40, NO 2027 Kjeller, Norway
Interests: materials science; modelling of materials by first-principles calculations; synthesis of nanomaterials; smart windows; solar cells; photocatalysis; photoelectrochemical cells
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Faculty of Product Design and Environment, Department of Product Design, Mechatronics and Environment, Transilvania University of Brasov, Eroilor 29, 500036 Brasov, Romania
Interests: environmental engineering; optoelectronic materials; nanomaterials; ceramics; chemical synthesis of nanoparticles; advanced oxidation processes; photocatalysis; water and wastewater treatment; nanomaterials toxicity; life cycle assessment
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

The MDPI journal Nanomaterials welcomes contributions to the Special Issue entitled "Applications of Nanomaterials for Electrocatalysis, Photocatalysis, Photoelectrochemical Solar Cells and Toxicity". The main objective of this Special Issue is to publish the latest and outstanding research results related to nanomaterials and their applications in electrocatalysis, photocatalysis, photoelectrochemical solar cells and toxicity.

The Special Issue aims at collecting perspectives, review articles, and technical papers on topics that include, but are not limited to:

  • Synthesis, physical and chemical properties of nanomaterials;
  • Applications of nanomaterials in photocatalysis, electrocatalysis, photoelectrochemical solar cells, and dyesensitized solar cells;
  • Toxicity of nanomaterials;
  • Life-cycle assessment;
  • Theoretical and experimental methods of study of nanomaterials. 

Dr. Smagul Karazhanov
Prof. Dr. Luminiţa Andronic
Guest Editors

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Keywords

  • nanoparticles
  • electrocatalysis
  • water splitting
  • photocatalysis
  • degradation
  • clean environment

Published Papers (8 papers)

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Research

13 pages, 3764 KiB  
Article
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 - 3 Feb 2024
Viewed by 902
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
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17 pages, 1962 KiB  
Article
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 825
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
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14 pages, 4156 KiB  
Article
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 - 7 Dec 2023
Cited by 1 | Viewed by 963
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
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14 pages, 6008 KiB  
Article
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 967
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
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15 pages, 3708 KiB  
Article
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 - 4 Jun 2023
Cited by 2 | Viewed by 1358
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
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17 pages, 4408 KiB  
Article
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 7 | Viewed by 1611
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
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15 pages, 3663 KiB  
Article
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 1412
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
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10 pages, 2399 KiB  
Article
An Electrochromic Ag-Decorated WO3−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 1692
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-WO3−x electrochromic heterostructure was synthesized for EC-SERS. Especially, the use of electrochromic WO3−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
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