The Importance of Shape-Tailoring at Nano- and Micro-Levels in Catalytic and Photocatalytic Applications

A special issue of Catalysts (ISSN 2073-4344). This special issue belongs to the section "Photocatalysis".

Deadline for manuscript submissions: closed (20 May 2023) | Viewed by 23423

Special Issue Editors

1. Department of Applied and Environmental Chemistry, Faculty of Natural Sciences and Informatics, Institute of Chemistry, University of Szeged, Szeged, Hungary
2. Faculty of Biology and Geology, Babeș-Bolyai University, Centre 3B, STAR-UBB, Cluj-Napoca, Romania
Interests: photocatalysis; ecotoxicology; environment–nanoparticle interaction; photochemistry
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Guest Editor
Faculty of Physics, Institute of Interdisciplinary Research in Bio-Nano-Sciences, Babes-Bolyai University, Cluj-Napoca, Romania
Interests: biomaterials; photocatalysts and graphene based materials
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Guest Editor
Faculty of Physics, Babeș-Bolyai University, M. Kogalniceanu 1, 400084 Cluj-Napoca, Romania
Interests: Raman and IR spectroscopy; plasmonics; SERS; nanostructures; pharmaceuticals; photocatalysts; carbon-based nanomaterials
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

We are all aware that we live in a world that provides constant challenges and hurdles. These issues are usually related to our everyday life and the sustainability of our home planet (energy sources, water, air, medical issues). Therefore, any scientific contribution to the already available processes and technologies is, and will be, critical in the near future. Nanotechnology is nowadays “The Technology” that answers the above-mentioned challenges. Nano- and micro-sized materials are those which will provide the solution, keeping in mind that every particle’s properties are defined by its shape or secondary organization level, the so-called hierarchical structures. The peculiarities of each crystal shape are defined by the unique structure of each exposed crystallographic facet, which can be tuned accordingly. Therefore, the present Special Issue will be focused on contributions in the field of (photo)catalysis, with special attention paid to the correlation between the catalytic and photocatalytic activity of a nano- or macro-sized material to the morphology, while taking into account the very complex network of dependencies based on the activity-structure-morphology triangle.

Dr. Zsolt Pap
Assoc. Prof. Dr. Lucian Baia
Assoc. Prof. Dr. Monica Baia
Guest Editors

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Keywords

  • (photo)catalysts
  • nano- and micro-sized materials
  • semiconductor oxides
  • noble metal nanoparticles
  • nanostructures
  • nanocomposites
  • shape-tailoring
  • plasmonics
  • carbon-based nanomaterials
  • pharmaceuticals

Published Papers (9 papers)

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Research

10 pages, 968 KiB  
Article
Operando Laboratory X-ray Absorption Spectroscopy and UV–Vis Study of Pt/TiO2 Photocatalysts during Photodeposition and Hydrogen Evolution Reactions
by Elizaveta G. Kozyr, Peter N. Njoroge, Sergei V. Chapek, Viktor V. Shapovalov, Alina A. Skorynina, Anna Yu. Pnevskaya, Alexey N. Bulgakov, Alexander V. Soldatov, Francesco Pellegrino, Elena Groppo, Silvia Bordiga, Lorenzo Mino and Aram L. Bugaev
Catalysts 2023, 13(2), 414; https://doi.org/10.3390/catal13020414 - 15 Feb 2023
Cited by 4 | Viewed by 2378
Abstract
Photocatalytic hydrogen (H2) production is a promising route for alternative energetics. Understanding structure–activity relationships is a crucial step towards the rational design of photocatalysts, which requires the application of operando spectroscopy under relevant working conditions. We performed an operando investigation on [...] Read more.
Photocatalytic hydrogen (H2) production is a promising route for alternative energetics. Understanding structure–activity relationships is a crucial step towards the rational design of photocatalysts, which requires the application of operando spectroscopy under relevant working conditions. We performed an operando investigation on a catalytic system during the photodeposition of Pt on TiO2 and photostimulated H2 production, using simultaneous laboratory X-ray absorption spectroscopy (XAS), UV–Vis spectroscopy, and mass spectrometry. XAS showed a progressive increase in Pt fluorescence for Pt deposited on TiO2 for over an hour, which is correlated with the signal of the produced H2. The final Pt/TiO2 catalyst contained Pt(0) particles. The electronic features corresponding to the Pt4+ species in the UV–Vis spectrum of the solution disappear as soon as UV radiation is applied in the presence of formic acid, which acts as a hole scavenger, resulting in the presence of Pt(0) particles in solution. Full article
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12 pages, 3421 KiB  
Article
Pulsed-Laser Induced Photolysis of Synthesizing Magnetic Fe3O4 Nanoparticles for Visible-Light Photocatalysis
by Bing-Yen Wang, Sheng-Yang Huang, Ya-Shing Hsiao, Pei-Ching Wei, Chia-Man Chou and Vincent K. S. Hsiao
Catalysts 2022, 12(11), 1459; https://doi.org/10.3390/catal12111459 - 17 Nov 2022
Cited by 6 | Viewed by 1651
Abstract
Our report is the first example describing the successful synthesis of magnetic Fe3O4 nanoparticles (NPs), for which we used pulsed-laser induced photolysis (PLIP). Compared with the previous method of using pulsed-laser ablation of a target, or strong energy of pulsed-laser [...] Read more.
Our report is the first example describing the successful synthesis of magnetic Fe3O4 nanoparticles (NPs), for which we used pulsed-laser induced photolysis (PLIP). Compared with the previous method of using pulsed-laser ablation of a target, or strong energy of pulsed-laser light to decompose precursors in generating a solvated-ion reaction, the PLIP method used here is dependent on hydrogen peroxide (H2O2) to generate a hydrolysis reaction. Energy-dispersive X-ray spectroscopy (EDS) and X-ray diffraction (XRD) were used to demonstrate the Fe3O4 crystalline structure of the synthesized NPs. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) images revealed that the average size of the NPs was about 20–50 nm. Regarding their magnetic characteristics, the synthesized NPs exhibited a saturation magnetization of 5.62 emu/g, remanence of 3.82 emu/g, and coercive force of 49.8 Oe. The photocatalytic experiments confirmed that the synthesized magnetic Fe3O4 NPs have visible light-degradation effects based on their ability to photocatalytically degrade methylene blue (MB). The MB degradation efficiency was 60–80% under white-light exposure for 180 min. This study presents a new route for synthesizing magnetic Fe3O4 NPs for their potential use in photocatalysis. Full article
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12 pages, 2192 KiB  
Article
Visible Light-Induced Photocatalyst with Au/TiO2 Nanocomposites Fabricated through Pulsed Laser-Induced Photolysis
by Bing-Yen Wang, Ya-Shing Hsiao, Pei-Ching Wei, Yuan-Tung Liu, Chih-Chien Chu and Vincent K. S. Hsiao
Catalysts 2022, 12(5), 564; https://doi.org/10.3390/catal12050564 - 20 May 2022
Cited by 7 | Viewed by 2167
Abstract
Gold–titanium oxide nanocomposites (Au–TiO2 NCPs) were fabricated through pulsed laser-induced photolysis (PIPS) and verified to be usable for the visible light catalytic degradation of methylene blue (MB). The PIPS method can produce a sufficient amount of NCPs quickly and has potential to [...] Read more.
Gold–titanium oxide nanocomposites (Au–TiO2 NCPs) were fabricated through pulsed laser-induced photolysis (PIPS) and verified to be usable for the visible light catalytic degradation of methylene blue (MB). The PIPS method can produce a sufficient amount of NCPs quickly and has potential to be commercialized. In contrast to other studies, we clarified the optical spectrum of the light sources, including peak power, bandwidth, and total intensity used for photodegradation reactions and discovered that the photodegradation efficiency of the produced Au–TiO2 NCPs in the wavelength range of 405 nm could reach 37% in 30 min due to the charge transfer between Au and TiO2. The control experiment shows that the addition of individual Au and TiO2 nanoparticles (NPs) to an MB solution has no enhancement of degradation ability under visible light illumination. The photodegradation of Au–TiO2 NCPs can be further improved by increasing the concentrations of auric acid and TiO2 NPs in a precursor under PIPS fabrication. Full article
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9 pages, 3466 KiB  
Article
Reduced Graphene Oxide Supported Zinc Tungstate Nanoparticles as Proficient Electro-Catalysts for Hydrogen Evolution Reactions
by Norah Alhokbany, Tansir Ahamad, Saad M. Alshehri and Jahangeer Ahmed
Catalysts 2022, 12(5), 530; https://doi.org/10.3390/catal12050530 - 9 May 2022
Cited by 2 | Viewed by 2056
Abstract
The nanocomposites of reduced graphene oxide (rGO) supported zinc tungstate nanoparticles (ZnWO4-NPs) receive considerable attention in electro-catalytic hydrogen evolution reactions (HER) and reveal significantly higher electro-catalytic performances than pure ZnWO4-NPs in alkaline media (i.e., 0.5 M KOH electrolyte). The [...] Read more.
The nanocomposites of reduced graphene oxide (rGO) supported zinc tungstate nanoparticles (ZnWO4-NPs) receive considerable attention in electro-catalytic hydrogen evolution reactions (HER) and reveal significantly higher electro-catalytic performances than pure ZnWO4-NPs in alkaline media (i.e., 0.5 M KOH electrolyte). The polarization studies show that the ZnWO4-NPs@rGO nanocomposites exhibit low energy loss and good electrode stability during electrochemical reactions for HER. Furthermore, the Tafel slope of ZnWO4-NPs@rGO nanocomposites is found to be approximately 149 mV/dec, which closely agrees with the reported Tafel values of the noble metal electrocatalyst. In contrast, the performance of the ZnWO4-NPs@rGO nanocomposite is found to be approximately 1.5 times higher than that of ZnWO4-NPs in hydrogen production efficiency. Our results emphasize the significance of the nanocomposites with enhanced electro-catalytic activities by lowering the energy loss during electro-catalysis in an alkaline medium. Full article
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19 pages, 4640 KiB  
Article
Tailoring g-C3N4 with Lanthanum and Cobalt Oxides for Enhanced Photoelectrochemical and Photocatalytic Activity
by Naseer Iqbal
Catalysts 2022, 12(1), 15; https://doi.org/10.3390/catal12010015 - 24 Dec 2021
Cited by 10 | Viewed by 3596
Abstract
Herein, the synthesis, characterization, and photoelectrochemical and photocatalytic characteristics of hydrothermally prepared La2O3–g-C3N4, CoO–g-C3N4, and La2O3–CoO–g-C3N4 are discussed. The XRD analysis and crystalline phases [...] Read more.
Herein, the synthesis, characterization, and photoelectrochemical and photocatalytic characteristics of hydrothermally prepared La2O3–g-C3N4, CoO–g-C3N4, and La2O3–CoO–g-C3N4 are discussed. The XRD analysis and crystalline phases unveiled the impregnation of La2O3 and CoO into g-C3N4. The microscopic analysis supports the formation of g-C3N4 nanoflakes and La2O3 and CoO nanoparticles embedded homogeneously in the La2O3–CoO–g-C3N4 nanocomposite, whereas the EDX comprehended their respective elemental composition and ratios. A bandgap energy of 2.38 eV for La2O3–CoO–g-C3N4 was calculated using the Tauc plot method, complementing high visible-light activity. The solar-driven water-splitting reaction exhibited significant photocurrent efficiency (~3.75 mA/cm2), augmenting the hydrogen generation by La2O3–CoO–g-C3N4 compared to that by pure g-C3N4, La2O3–g-C3N4, and CoO–g-C3N4 in 0.5 M Na2SO4 electrolyte. The synergistic effect of La2O3 and CoO impregnation with g-C3N4 led to effective division of the photogenerated charge transporters, enhancing the photocatalytic hydrogen generation by the photocatalysts. Furthermore, photocatalytic pollutant removal, namely greater than 90% decomposition of methylene blue (MB) from water, was investigated with a pseudo-first-order reaction kinetics under 1 sun visible-light irradiation. Thus, La2O3–CoO–g-C3N4 nanocomposite was found to be a prospective material for harnessing solar energy. Full article
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11 pages, 7129 KiB  
Article
Synthesis, Characterization and Enhanced Visible Light Photocatalytic Performance of ZnWO4-NPs@rGO Nanocomposites
by Norah Alhokbany, Saad M. Alshehri and Jahangeer Ahmed
Catalysts 2021, 11(12), 1536; https://doi.org/10.3390/catal11121536 - 16 Dec 2021
Cited by 10 | Viewed by 2391
Abstract
ZnWO4 nanoparticles on reduced graphene oxide (ZnWO4-NPs@rGO) nanocomposites were synthesized using the hydrothermal method. Structural, morphological, optical, and photocatalytic studies of the ZnWO4-NPs@rGO nanocomposites were successfully investigated. Photo-catalytic performances of the ZnWO4-NPs@rGO nanocomposites were examined for [...] Read more.
ZnWO4 nanoparticles on reduced graphene oxide (ZnWO4-NPs@rGO) nanocomposites were synthesized using the hydrothermal method. Structural, morphological, optical, and photocatalytic studies of the ZnWO4-NPs@rGO nanocomposites were successfully investigated. Photo-catalytic performances of the ZnWO4-NPs@rGO nanocomposites were examined for the degradation of hazardous methylene blue dye (HMBD) in a neutral medium. ZnWO4-NPs@rGO nanocomposites show superior photo-catalytic performances over pure ZnWO4 nanoparticles. ZnWO4-NPs@rGO nanocomposites degrade ~98% dye while pure ZnWO4 nanoparticles degrade ~53% dye in 120 min. The prepared nanocomposites also show excellent recycled photo-catalytic efficiencies over multiple cycles. Full article
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15 pages, 4570 KiB  
Article
Oxygen-Deficient WO3/TiO2/CC Nanorod Arrays for Visible-Light Photocatalytic Degradation of Methylene Blue
by Liaochuan Jiang, Xingyuan Gao, Shaoling Chen, Jangam Ashok and Sibudjing Kawi
Catalysts 2021, 11(11), 1349; https://doi.org/10.3390/catal11111349 - 9 Nov 2021
Cited by 12 | Viewed by 2136
Abstract
At present, TiO2 is one of the most widely used photocatalytic materials. However, the narrow response range to light limits the photocatalytic performance. Herein, we reported a successful construction of self-doped R-WO3/R-TiO2/CC nanocomposites on flexible carbon cloth (CC) [...] Read more.
At present, TiO2 is one of the most widely used photocatalytic materials. However, the narrow response range to light limits the photocatalytic performance. Herein, we reported a successful construction of self-doped R-WO3/R-TiO2/CC nanocomposites on flexible carbon cloth (CC) via electrochemical reduction to increase the oxygen vacancies (Ovs), resulting in an enhanced separation efficiency of photo-induced charge carriers. The photocurrent of R-WO3/R-TiO2/CC at −1.6 V (vs. SCE) was 2.6 times higher than that of WO3/TiO2/CC, which suggested that Ovs could improve the response to sunlight. Moreover, the photocatalytic activity of R-WO3/TiO2/CC was explored using methylene blue (MB). The degradation rate of MB could reach 68%, which was 1.3 times and 3.8 times higher than that of WO3/TiO2/CC and TiO2/CC, respectively. Furthermore, the solution resistance and charge transfer resistance of R-WO3/R-TiO2/CC were obviously decreased. Therefore, the electrochemical reduction of nanomaterials enabled a promoted separation of photogenerated electron–hole pairs, leading to high photocatalytic activity. Full article
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25 pages, 7813 KiB  
Article
Synthesis Design of Electronegativity Dependent WO3 and WO3∙0.33H2O Materials for a Better Understanding of TiO2/WO3 Composites’ Photocatalytic Activity
by István Székely, Endre-Zsolt Kedves, Zsolt Pap and Monica Baia
Catalysts 2021, 11(7), 779; https://doi.org/10.3390/catal11070779 - 27 Jun 2021
Cited by 7 | Viewed by 3257
Abstract
The design of a semiconductor or a composite semiconductor system—with applications in materials science—is complex because its morphology and structure depend on several parameters. These parameters are the precursor type, solvent, pH of the solution, synthesis approach, or shaping agents. This study gives [...] Read more.
The design of a semiconductor or a composite semiconductor system—with applications in materials science—is complex because its morphology and structure depend on several parameters. These parameters are the precursor type, solvent, pH of the solution, synthesis approach, or shaping agents. This study gives meaningful insight regarding the synthesis design of such WO3 materials. By systematically alternating the precursor (sodium tungstate dihydrate—NWH, or ammonium tungstate hydrate—AMT), subsequently shaping the agents (halide salts—NaX, KX, or hydrohalic acids—HX; X = F, Cl, Br, I), we have obtained WO3 semiconductors by hydrothermal treatment, which in composite systems can enhance the commercial TiO2 photocatalytic activity. We investigated three sample series: WO3-NWH-NaX/WO3-NWH-KX and, subsequently, WO3-AMT-HX. The presence of W+5 centers was evidenced by Raman and X-ray photoelectron spectroscopy. W+5 and W+6 species affected the band gap values of the NaX and KX series; a higher percentage of W+5 and, subsequently, W+6 caused a redshift, while, regarding the HX series, it led to a blue shift. Increased electronegativity of the halide anions has an unfavorable effect on the composites’ photoactivity. In contrast, in the case of hydrohalic acids, it had a positive impact. Full article
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15 pages, 2707 KiB  
Article
Solvothermal Crystallization of Ag/AgxO-AgCl Composites: Effect of Different Chloride Sources/Shape-Tailoring Agents
by Zsejke-Réka Tóth, Saurav Kumar Maity, Tamás Gyulavári, Enikő Bárdos, Lucian Baia, Gábor Kovács, Seema Garg, Zsolt Pap and Klara Hernadi
Catalysts 2021, 11(3), 379; https://doi.org/10.3390/catal11030379 - 15 Mar 2021
Cited by 2 | Viewed by 2323
Abstract
In the present work, AgCl microcrystals were obtained by solvothermal crystallization to investigate the effect of H+, Na+, K+, and different shape-tailoring agents (non-ionic: polyvinylpyrrolidone vs. anionic: sodium dodecyl sulfate) on the textural and photocatalytic properties of [...] Read more.
In the present work, AgCl microcrystals were obtained by solvothermal crystallization to investigate the effect of H+, Na+, K+, and different shape-tailoring agents (non-ionic: polyvinylpyrrolidone vs. anionic: sodium dodecyl sulfate) on the textural and photocatalytic properties of the samples. The crystallization process resulted in secondary products, such as AgxO or Ag, AgClO3, AgClO4, which were further transformed during the photocatalytic tests. The most efficient photocatalyst (assessed for methyl orange degradation) was synthesized using HCl, as a chloride source and polyvinylpyrrolidone, as a shape-tailoring agent. Therefore, the ability of polyvinylpyrrolidone to enhance the photocatalytic activity was also investigated, and it was found that the addition of 0.6 g polyvinylpyrrolidone resulted in the most efficient photocatalyst. Moreover, AgxO, being a charge separator, could play a critical role in the photocatalytic process, while reversibly transforming to Ag back and forth. Full article
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