Research

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16 pages, 3387 KiB

Open AccessArticle

Investigation of the Photocatalytic Performance, Mechanism, and Degradation Pathways of Rhodamine B with Bi₂O₃ Microrods under Visible-Light Irradiation

by Dechong Ma, Jiawei Tang, Guowen He and Sai Pan

Materials 2024, 17(4), 957; https://0-doi-org.brum.beds.ac.uk/10.3390/ma17040957 - 19 Feb 2024

Cited by 1 | Viewed by 569

Abstract

In the present work, the photodegradation of Rhodamine B with different pH values by using Bi₂O₃ microrods under visible-light irradiation was studied in terms of the dye degradation efficiency, active species, degradation mechanism, and degradation pathway. X-ray diffractometry, polarized optical [...] Read more.

In the present work, the photodegradation of Rhodamine B with different pH values by using Bi₂O₃ microrods under visible-light irradiation was studied in terms of the dye degradation efficiency, active species, degradation mechanism, and degradation pathway. X-ray diffractometry, polarized optical microscopy, scanning electron microscopy, fluorescence spectrophotometry, diffuse reflectance spectra, Brunauer–Emmett–Teller, X-ray photoelectron spectroscopy, Fourier-transform infrared spectroscopy, UV–visible spectrophotometry, total organic carbon, and liquid chromatography–mass spectroscopy analysis techniques were used to analyze the crystal structure, morphology, surface structures, band gap values, catalytic performance, and mechanistic pathway. The photoluminescence spectra and diffuse reflectance spectrum (the band gap values of the Bi₂O₃ microrods are 2.79 eV) reveals that the absorption spectrum extended to the visible region, which resulted in a high separation and low recombination rate of electron–hole pairs. The photodegradation results of Bi₂O₃ clearly indicated that Rhodamine B dye had removal efficiencies of about 97.2%, 90.6%, and 50.2% within 120 min at the pH values of 3.0, 5.0, and 7.0, respectively. In addition, the mineralization of RhB was evaluated by measuring the effect of Bi₂O₃ on chemical oxygen demand and total organic carbon at the pH value of 3.0. At the same time, quenching experiments were carried out to understand the core reaction species involved in the photodegradation of Rhodamine B solution at different pH values. The results of X-ray photoelectron spectroscopy, Fourier-transform infrared spectroscopy, and X-ray diffractometer analysis of pre- and post-Bi₂O₃ degradation showed that BiOCl was formed on the surface of Bi₂O₃, and a BiOCl/Bi₂O₃ heterojunction was formed after acid photocatalytic degradation. Furthermore, the catalytic degradation of active substances and the possible mechanism of the photocatalytic degradation of Rhodamine B over Bi₂O₃ at different pH values were analyzed based on the results of X-ray diffractometry, radical capture, Fourier-transform infrared spectroscopy, total organic carbon analysis, and X-ray photoelectron spectroscopy. The degradation intermediates of Rhodamine B with the Bi₂O₃ photocatalyst in visible light were also identified with the assistance of liquid chromatography–mass spectroscopy. Full article

(This article belongs to the Special Issue Advanced Nanostructured Materials for Catalytic Applications)

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12 pages, 2846 KiB

Open AccessArticle

Influence of the Mesoporosity of Hierarchical ZSM-5 in Toluene Alkylation by Methanol

by Lucie Desmurs, Claudia Cammarano, Olinda Gimello, Anne Galarneau and Vasile Hulea

Materials 2023, 16(21), 6872; https://0-doi-org.brum.beds.ac.uk/10.3390/ma16216872 - 26 Oct 2023

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Abstract

Among the different strategies to design highly shape-selective ZSM-5 to obtain para-xylene through toluene alkylation with methanol, the introduction of mesopores to increase reactant and product diffusion has been proposed but barely studied. In this study, we prepared mesoporous ZSM-5 catalysts, named ZSM5-MT(x), [...] Read more.

Among the different strategies to design highly shape-selective ZSM-5 to obtain para-xylene through toluene alkylation with methanol, the introduction of mesopores to increase reactant and product diffusion has been proposed but barely studied. In this study, we prepared mesoporous ZSM-5 catalysts, named ZSM5-MT(x), from commercial ZSM-5 (Si/Al = 15), using a two-step micelle-templating procedure with octadecyltrimethylammonium bromide as a surfactant in basic medium (x = NaOH/Si). These materials were used as catalysts for the alkylation of toluene by methanol at a low contact time to avoid thermodynamic equilibrium of the xylene isomers. Compared to the parent ZSM-5, the mesoporous ZSM5-MT(x) catalysts did not improve the para-xylene selectivity, revealing that the strategy of increasing diffusion in the catalyst is not a good strategy to follow. However, ZSM5-MT(0.5) showed less deactivation on stream than the parent ZSM-5. Therefore, introducing mesopores to ZSM-5 could be interesting to explore, combined with another strategy of shape selectivity, such as the passivation of the external surface acidity. Full article

(This article belongs to the Special Issue Advanced Nanostructured Materials for Catalytic Applications)

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16 pages, 2311 KiB

Open AccessArticle

Hydrothermal Synthesis of Heterostructured g-C₃N₄/Ag–TiO₂ Nanocomposites for Enhanced Photocatalytic Degradation of Organic Pollutants

by Agidew Sewnet, Esayas Alemayehu, Mulualem Abebe, Dhakshnamoorthy Mani, Sabu Thomas and Bernd Lennartz

Materials 2023, 16(15), 5497; https://0-doi-org.brum.beds.ac.uk/10.3390/ma16155497 - 07 Aug 2023

Cited by 1 | Viewed by 1285

Abstract

In this study, heterostructured g-C₃N₄/Ag–TiO₂ nanocomposites were successfully fabricated using an easily accessible hydrothermal route. Various analytical tools were employed to investigate the surface morphology, crystal structure, specific surface area, and optical properties of as-synthesized samples. XRD and [...] Read more.

In this study, heterostructured g-C₃N₄/Ag–TiO₂ nanocomposites were successfully fabricated using an easily accessible hydrothermal route. Various analytical tools were employed to investigate the surface morphology, crystal structure, specific surface area, and optical properties of as-synthesized samples. XRD and TEM characterization results provided evidence of the successful fabrication of the ternary g-C₃N₄/Ag–TiO₂ heterostructured nanocomposite. The heterostructured g-C₃N₄/Ag–TiO₂ nanocomposite exhibited the best degradation efficiency of 98.04% against rhodamine B (RhB) within 180 min under visible LED light irradiation. The g-C₃N₄/Ag–TiO₂ nanocomposite exhibited an apparent reaction rate constant 13.16, 4.7, and 1.33 times higher than that of TiO₂, Ag–TiO₂, and g-C₃N₄, respectively. The g-C₃N₄/Ag–TiO₂ ternary composite demonstrated higher photocatalytic activity than pristine TiO₂ and binary Ag–TiO₂ photocatalysts for the degradation of RhB under visible LED light irradiation. The improved photocatalytic performance of the g-C₃N₄/Ag–TiO₂ nanocomposite can be attributed to the formation of an excellent heterostructure between TiO₂ and g-C₃N₄ as well as the incorporation of Ag nanoparticles, which promoted efficient charge carrier separation and transfer and suppressed the rate of recombination. Therefore, this study presents the development of heterostructured g-C₃N₄/Ag–TiO₂ nanocomposites that exhibit excellent photocatalytic performance for the efficient degradation of harmful organic pollutants in wastewater, making them promising candidates for environmental remediation. Full article

(This article belongs to the Special Issue Advanced Nanostructured Materials for Catalytic Applications)

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12 pages, 6716 KiB

Open AccessArticle

Formation Pathways of Lath-Shaped WO₃ Nanosheets and Elemental W Nanoparticles from Heating of WO₃ Nanocrystals Studied via In Situ TEM

by Xiaodan Chen and Marijn A. van Huis

Materials 2023, 16(3), 1291; https://0-doi-org.brum.beds.ac.uk/10.3390/ma16031291 - 02 Feb 2023

Cited by 2 | Viewed by 1461

Abstract

WO₃ is a versatile material occurring in many polymorphs, and is used in nanostructured form in many applications, including photocatalysis, gas sensing, and energy storage. We investigated the thermal evolution of cubic-phase nanocrystals with a size range of 5–25 nm by means [...] Read more.

WO₃ is a versatile material occurring in many polymorphs, and is used in nanostructured form in many applications, including photocatalysis, gas sensing, and energy storage. We investigated the thermal evolution of cubic-phase nanocrystals with a size range of 5–25 nm by means of in situ heating in the transmission electron microscope (TEM), and found distinct pathways for the formation of either 2D WO₃ nanosheets or elemental W nanoparticles, depending on the initial concentration of deposited WO₃ nanoparticles. These pristine particles were stable up to 600 °C, after which coalescence and fusion of the nanocrystals were observed. Typically, the nanocrystals transformed into faceted nanocrystals of elemental body-centered-cubic W after annealing to 900 °C. However, in areas where the concentration of dropcast WO₃ nanoparticles was high, at a temperature of 900 °C, considerably larger lath-shaped nanosheets (extending for hundreds of nanometers in length and up to 100 nm in width) were formed that are concluded to be in monoclinic WO₃ or WO₂.₇ phases. These lath-shaped 2D particles, which often curled up from their sides into folded 2D nanosheets, are most likely formed from the smaller nanoparticles through a solid–vapor–solid growth mechanism. The findings of the in situ experiments were confirmed by ex situ experiments performed in a high-vacuum chamber. Full article

(This article belongs to the Special Issue Advanced Nanostructured Materials for Catalytic Applications)

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10 pages, 2704 KiB

Open AccessCommunication

Electrodeposition of Stable Noble-Metal-Free Co-P Electrocatalysts for Hydrogen Evolution Reaction

by Jeongwon Kim, Yu Jin Jang and Yoon Hee Jang

Materials 2023, 16(2), 593; https://0-doi-org.brum.beds.ac.uk/10.3390/ma16020593 - 07 Jan 2023

Cited by 4 | Viewed by 1765

Abstract

Hydrogen production via water splitting has been extensively explored over the past few decades, and considerable effort has been directed toward finding more reactive and cost-effective electrocatalysts by engineering their compositions, shapes, and crystal structures. In this study, we developed hierarchical cobalt phosphide [...] Read more.

Hydrogen production via water splitting has been extensively explored over the past few decades, and considerable effort has been directed toward finding more reactive and cost-effective electrocatalysts by engineering their compositions, shapes, and crystal structures. In this study, we developed hierarchical cobalt phosphide (Co-P) nanosphere assemblies as non-noble metal electrocatalysts via one-step electrodeposition. The morphologies of the Co-P nanostructures and their electrocatalytic activities towards the hydrogen evolution reactions (HER) were controlled by the applied potentials during electrodeposition. The physicochemical properties of the as-prepared Co-P nanostructures in this study were characterized by field-emission scanning electron microscopy, X-ray photoemission spectroscopy and X-ray diffraction. Linear sweep voltammetry revealed that the Co-P grown at −0.9 V showed the best HER performance exhibiting the highest electrochemical active surface area and lowest interfacial charge transfer resistance. The Co-P electrocatalysts showed superior long-term stability to electrodeposited Pt, indicating their potential benefits. Full article

(This article belongs to the Special Issue Advanced Nanostructured Materials for Catalytic Applications)

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15 pages, 7240 KiB

Open AccessArticle

Assessment of the Synergetic Performance of Nanostructured CeO₂-SnO₂/Al₂O₃ Mixed Oxides on Automobile Exhaust Control

by Varuna Jayachandran, Vishnu Shankar Dhandapani, Elango Muniappan, Dongkyou Park, Byungki Kim, A. P. Arun and P. R. Ayyappan

Materials 2022, 15(23), 8460; https://0-doi-org.brum.beds.ac.uk/10.3390/ma15238460 - 28 Nov 2022

Cited by 1 | Viewed by 1178

Abstract

In order to control diesel exhaust emission, CeO₂-SnO₂/Al₂O₃ (CTA) mixed oxides were prepared and coated on perforated stainless steel (SS) filter plates, and the catalytic activities were analyzed in this work. The CeO₂-SnO₂ [...] Read more.

In order to control diesel exhaust emission, CeO₂-SnO₂/Al₂O₃ (CTA) mixed oxides were prepared and coated on perforated stainless steel (SS) filter plates, and the catalytic activities were analyzed in this work. The CeO₂-SnO₂ (different compositions of Ce/Sn—2:8; 1:1; 8:2) composites and Al₂O₃ were prepared separately via a co-precipitation approach, and CeO₂-SnO₂/Al₂O₃ (CTA) mixed oxides were attained by mechanical mixing of 75 wt% CeO₂-SnO₂ composites with 25 wt% Al₂O₃. X-ray diffraction (XRD) and Raman spectroscopy were performed for all three CeO₂-SnO₂/Al₂O₃ (CTA) mixed oxides; the CeO₂-SnO₂/Al₂O₃ (Ce/Sn-1:1) sample confirmed the presence of cubic and tetragonal mixed faces, which enhances the redox nature (catalytic activities). Various characterizations such as high-resolution transmission electron microscopy (HRTEM), Brunauer–Emmett–Teller (BET) analysis, X-ray photoelectron spectroscopy (XPS), and a scanning electron microscope (SEM) were employed on CeO₂-SnO₂/Al₂O₃ (Ce/Sn-1:1) sample to investigate the structural, textural, compositional, and morphological properties. The CeO₂-SnO₂/Al₂O₃ (Ce/Sn-1:1) sample was coated on a perforated stainless steel (SS) filter plate via a simple, cost-effective, and novel method, and an exhaust emission test for various compression ratios (CR), injection pressure (IP), and load (L) was completed using an AVL Digas analyzer. The CeO₂-SnO₂/Al₂O₃ (Ce/Sn-1:1) sample, with a size of 10.22 nm and a high surface area of about 73 m² g⁻¹, exhibit appreciable catalytic properties. Full article

(This article belongs to the Special Issue Advanced Nanostructured Materials for Catalytic Applications)

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Review

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26 pages, 8334 KiB

Open AccessReview

Multicomponent Metal Oxide- and Metal Hydroxide-Based Electrocatalysts for Alkaline Water Splitting

by Goeun Lee, Sang Eon Jun, Yujin Kim, In-Hyeok Park, Ho Won Jang, Sun Hwa Park and Ki Chang Kwon

Materials 2023, 16(8), 3280; https://0-doi-org.brum.beds.ac.uk/10.3390/ma16083280 - 21 Apr 2023

Cited by 10 | Viewed by 2601

Abstract

Developing cost-effective, highly catalytic active, and stable electrocatalysts in alkaline electrolytes is important for the development of highly efficient anion-exchange membrane water electrolysis (AEMWE). To this end, metal oxides/hydroxides have attracted wide research interest for efficient electrocatalysts in water splitting owing to their [...] Read more.

Developing cost-effective, highly catalytic active, and stable electrocatalysts in alkaline electrolytes is important for the development of highly efficient anion-exchange membrane water electrolysis (AEMWE). To this end, metal oxides/hydroxides have attracted wide research interest for efficient electrocatalysts in water splitting owing to their abundance and tunable electronic properties. It is very challenging to achieve an efficient overall catalytic performance based on single metal oxide/hydroxide-based electrocatalysts due to low charge mobilities and limited stability. This review is mainly focused on the advanced strategies to synthesize the multicomponent metal oxide/hydroxide-based materials that include nanostructure engineering, heterointerface engineering, single-atom catalysts, and chemical modification. The state of the art of metal oxide/hydroxide-based heterostructures with various architectures is extensively discussed. Finally, this review provides the fundamental challenges and perspectives regarding the potential future direction of multicomponent metal oxide/hydroxide-based electrocatalysts. Full article

(This article belongs to the Special Issue Advanced Nanostructured Materials for Catalytic Applications)

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24 pages, 5048 KiB

Open AccessReview

Recent Advances in Water-Splitting Electrocatalysts Based on Electrodeposition

by Yujin Kim, Sang Eon Jun, Goeun Lee, Seunghoon Nam, Ho Won Jang, Sun Hwa Park and Ki Chang Kwon

Materials 2023, 16(8), 3044; https://0-doi-org.brum.beds.ac.uk/10.3390/ma16083044 - 12 Apr 2023

Cited by 8 | Viewed by 3173

Abstract

Green hydrogen is being considered as a next-generation sustainable energy source. It is created electrochemically by water splitting with renewable electricity such as wind, geothermal, solar, and hydropower. The development of electrocatalysts is crucial for the practical production of green hydrogen in order [...] Read more.

Green hydrogen is being considered as a next-generation sustainable energy source. It is created electrochemically by water splitting with renewable electricity such as wind, geothermal, solar, and hydropower. The development of electrocatalysts is crucial for the practical production of green hydrogen in order to achieve highly efficient water-splitting systems. Due to its advantages of being environmentally friendly, economically advantageous, and scalable for practical application, electrodeposition is widely used to prepare electrocatalysts. There are still some restrictions on the ability to create highly effective electrocatalysts using electrodeposition owing to the extremely complicated variables required to deposit uniform and large numbers of catalytic active sites. In this review article, we focus on recent advancements in the field of electrodeposition for water splitting, as well as a number of strategies to address current issues. The highly catalytic electrodeposited catalyst systems, including nanostructured layered double hydroxides (LDHs), single-atom catalysts (SACs), high-entropy alloys (HEAs), and core-shell structures, are intensively discussed. Lastly, we offer solutions to current problems and the potential of electrodeposition in upcoming water-splitting electrocatalysts. Full article

(This article belongs to the Special Issue Advanced Nanostructured Materials for Catalytic Applications)

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