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13 pages, 3649 KiB

Open AccessArticle

Enhancing the Photocatalytic Activity of Lead-Free Halide Perovskite Cs₃Bi₂I₉ by Compositing with Ti₃C₂ MXene

by Tao Tang, Xiaoyu Dou, Haoran Zhang, Hexu Wang, Ming Li, Guanghui Hu, Jianfeng Wen and Li Jiang

Molecules 2024, 29(21), 5096; https://doi.org/10.3390/molecules29215096 - 28 Oct 2024

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Abstract

In recent years, halide perovskite materials have become widely used in solar cells, photovoltaics, and LEDs, as well as photocatalysis. Lead-free perovskite Cs₃Bi₂I₉ has been demonstrated as an effective photocatalyst; however, the fast recombination of the photogenerated carriers [...] Read more.

In recent years, halide perovskite materials have become widely used in solar cells, photovoltaics, and LEDs, as well as photocatalysis. Lead-free perovskite Cs₃Bi₂I₉ has been demonstrated as an effective photocatalyst; however, the fast recombination of the photogenerated carriers hinders further improvements of its photocatalytic activity. In this work, Ti₃C₂ was composited with Cs₃Bi₂I₉ to promote the transfer and separation of photogenerated carriers, and thus the pollutant degradation efficiency was effectively improved. The visible-light photocatalytic reduction of Cs₃Bi₂I₉/Ti₃C₂ on rhodamine B (RhB), methylene blue (MB), and malachite green (MG) was as high as 97.3%, 96%, and 98.8%, respectively, improvements of almost 31.2%, 37.8%, and 37.2% compared to that of sole Cs₃Bi₂I₉. Our study provides a simple way to enhance the photocatalytic activity of lead-free halide perovskites. Full article

(This article belongs to the Special Issue Advances in Composite Photocatalysts)

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17 pages, 2816 KiB

Open AccessArticle

Z-Scheme BiVO₄/g-C₃N₄ Photocatalyst—With or Without an Electron Mediator?

by Tomasz Łęcki, Kamila Zarębska, Ewelina Wierzyńska, Krzysztof P. Korona, Paulina Chyży, Piotr Piotrowski and Magdalena Skompska

Molecules 2024, 29(21), 5092; https://doi.org/10.3390/molecules29215092 - 28 Oct 2024

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Abstract

The hybrid system BiVO₄/g-C₃N₄ is a prospective photocatalyst because of the favorable mutual alignment of the energy bands of both semiconductors. However, the path of the photocatalytic process is still unclear because of contradictory information in the literature [...] Read more.

The hybrid system BiVO₄/g-C₃N₄ is a prospective photocatalyst because of the favorable mutual alignment of the energy bands of both semiconductors. However, the path of the photocatalytic process is still unclear because of contradictory information in the literature on whether the mechanism of charge carrier separation at the BiVO₄/g-C₃N₄ interface is band-to-band or Z-scheme. In this work, we clarified this issue by comparative photocatalytic studies with the use of systems without a mediator and with different kinds of mediators including Au nanoparticles, fullerene derivatives, and the Fe³⁺/Fe²⁺ redox couple. Additionally, the charge transfer dynamics at the BiVO₄/g-C₃N₄ and BiVO₄/mediator/g-C₃N₄ interfaces were investigated by time-resolved photoluminescence (TRPL) measurements, while the influence of the mediator on the surface recombination of the charge carriers was verified by intensity-modulated photocurrent spectroscopy (IMPS). We proved that the charge carrier separation at the BiVO₄/g-C₃N₄ interface occurs according to the mechanism typical for a heterojunction of type II, while the incorporation of the mediator between BiVO₄ and g-C₃N₄ leads to the Z-scheme mechanism. Moreover, a very strong synergetic effect on caffeine (CAF) degradation rate was found for the system BiVO₄/Au/g-C₃N₄ in the presence of Fe³⁺ ions in the CAF solution. Full article

(This article belongs to the Special Issue Advances in Composite Photocatalysts)

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17 pages, 5119 KiB

Open AccessArticle

Fabrication of Active Z-Scheme Sr₂MgSi₂O₇: Eu²⁺, Dy³⁺/COF Photocatalyst for Round-the-Clock Efficient Removal of Total Cr

by Meng Xu, Junshu Wu, Mupeng Zheng and Jinshu Wang

Molecules 2024, 29(18), 4327; https://doi.org/10.3390/molecules29184327 - 12 Sep 2024

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Abstract

Photoreduction is recognized as a desirable treatment method for hexavalent chromium (Cr(VI)). However, it has been limited by the intermittent solar flux and limited light absorption. In this work, a novel Z-scheme photocatalyst combining a covalent organic framework (COF) with Eu²⁺, [...] Read more.

Photoreduction is recognized as a desirable treatment method for hexavalent chromium (Cr(VI)). However, it has been limited by the intermittent solar flux and limited light absorption. In this work, a novel Z-scheme photocatalyst combining a covalent organic framework (COF) with Eu²⁺, Dy³⁺ co-doped Sr₂MgSi₂O₇ (Sr₂MgSi₂O₇:Eu²⁺, Dy³⁺) is synthesized, which shows the high spectral conversion efficiency and works efficiently in both light irradiation and dark for Cr(VI) reduction. Sr₂MgSi₂O₇:Eu²⁺, Dy³⁺ serves as both an electron transfer station and active sites for COF molecule activation, thus resulting in 100% photoreduction of Cr(VI) (50 mL, 10 mg/L) with high light stability and over 1 h dark activity. Moreover, the XPS and FT-IR analyses reveal the existence of functional groups (Si-OH on Sr₂MgSi₂O₇:Eu²⁺, Dy³⁺, and -NH- on COF_TP-TTA) on the composited catalyst as active sites to adsorb the resultant Cr(III) species, demonstrating a synergistic effect for total Cr removal. This work provides an alternative method for the design of a round-the-clock photocatalyst for Cr(VI) reduction, allowing a versatile solid surface activation for establishing a more energy efficient and robust photocatalysis process for Cr pollution cleaning. Full article

(This article belongs to the Special Issue Advances in Composite Photocatalysts)

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15 pages, 4627 KiB

Open AccessArticle

Enhanced Photocatalytic Performance under Ultraviolet and Visible Light Illumination of ZnO Thin Films Prepared by Modified Sol-Gel Method

by Radka Gegova-Dzhurkova, Diana Nesheva, Irina Stambolova, Katerina Zaharieva, Valeri Dzhurkov and Ilko Miloushev

Molecules 2024, 29(17), 4005; https://doi.org/10.3390/molecules29174005 - 24 Aug 2024

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Abstract

Semiconductor oxides are frequently used as active photocatalysts for the degradation of organic agents in water polluted by domestic industry. In this study, sol-gel ZnO thin films with a grain size in the range of 7.5–15.7 nm were prepared by applying a novel [...] Read more.

Semiconductor oxides are frequently used as active photocatalysts for the degradation of organic agents in water polluted by domestic industry. In this study, sol-gel ZnO thin films with a grain size in the range of 7.5–15.7 nm were prepared by applying a novel two-step drying procedure involving hot air treatment at 90–95 °C followed by conventional furnace drying at 140 °C. For comparison, layers were made by standard furnace drying. The effect of hot air treatment on the film surface morphology, transparency, and photocatalytic behavior during the degradation of Malachite Green azo dye in water under ultraviolet or visible light illumination is explored. The films treated with hot air demonstrate significantly better photocatalytic activity under ultraviolet irradiation than the furnace-dried films, which is comparable with the activity of unmodified ZnO nanocrystal powders. The achieved percentage of degradation is 78–82% under ultraviolet illumination and 85–90% under visible light illumination. Multiple usages of the hot air-treated films (up to six photocatalytic cycles) are demonstrated, indicating improved photo-corrosion resistance. The observed high photocatalytic activity and good photo-corrosion stability are related to the hot air treatment, which causes a reduction of oxygen vacancies and other defects and the formation of interstitial oxygen and/or zinc vacancies in the films. Full article

(This article belongs to the Special Issue Advances in Composite Photocatalysts)

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13 pages, 3465 KiB

Open AccessArticle

Facilitated Unidirectional Electron Transmission by Ru Nano Particulars Distribution on MXene Mo₂C@g-C₃N₄ Heterostructures for Enhanced Photocatalytic H₂ Evolution

by Qiuyu Chen, Zonghan Huang, Meng Liu, Xiaoping Li, Yuxuan Du, Xiaobao Chen, Dahu Ding, Shengjiong Yang, Yang Chen and Rongzhi Chen

Molecules 2024, 29(7), 1684; https://doi.org/10.3390/molecules29071684 - 8 Apr 2024

Cited by 3 | Viewed by 1277

Abstract

Precious metals exhibit promising potential for the hydrogen evolution reaction (HER), but their limited abundance restricts widespread utilization. Loading precious metal nanoparticles (NPs) on 2D/2D heterojunctions has garnered considerable interest since it saves precious metal consumption and facilitates unidirectional electron transmission from semiconductors [...] Read more.

Precious metals exhibit promising potential for the hydrogen evolution reaction (HER), but their limited abundance restricts widespread utilization. Loading precious metal nanoparticles (NPs) on 2D/2D heterojunctions has garnered considerable interest since it saves precious metal consumption and facilitates unidirectional electron transmission from semiconductors to active sites. In this study, Ru NPs loaded on MXenes Mo₂C by an in-site simple strategy and then formed 2D/2D heterojunctions with 2D g-C₃N₄ (CN) via electrostatic self-assembly were used to enhance photocatalytic H₂ evolution. Evident from energy band structure analyses such as UV-vis and TRPL, trace amounts of Ru NPs as active sites significantly improve the efficiency of the hydrogen evolution reaction. More interestingly, MXene Mo₂C, as substrates for supporting Ru NPs, enriches photoexcited electrons from CN, thereby enhancing the unidirectional electron transmission. As a result, the combination of Ru-Mo₂C and CN constructs a composite heterojunction (Ru-Mo₂C@CN) that shows an improved H₂ production rate at 1776.4 μmol∙g⁻¹∙h⁻¹ (AQE 3.58% at 400 nm), which is facilitated by the unidirectional photogenerated electron transmission from the valence band on CN to the active sites on Ru (CN→Mo₂C→Ru). The study offers fresh perspectives on accelerated unidirectional photogenerated electron transmission and saved precious metal usage in photocatalytic systems. Full article

(This article belongs to the Special Issue Advances in Composite Photocatalysts)

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17 pages, 7171 KiB

Open AccessArticle

Achieving Highly Efficient Photocatalytic Hydrogen Evolution through the Construction of g-C₃N₄@PdS@Pt Nanocomposites

by Ligang Ma, Chao Lin, Wenjun Jiang, Shun Yan, Huilin Jiang, Xiang Song, Xiaoqian Ai, Xiaoxiao Cao and Yihuan Ding

Molecules 2024, 29(2), 493; https://doi.org/10.3390/molecules29020493 - 19 Jan 2024

Cited by 3 | Viewed by 1388

Abstract

Selective supported catalysts have emerged as a promising approach to enhance carrier separation, particularly in the realm of photocatalytic hydrogen production. Herein, a pioneering exploration involves the loading of PdS and Pt catalyst onto g-C₃N₄ nanosheets to construct g-C₃ [...] Read more.

Selective supported catalysts have emerged as a promising approach to enhance carrier separation, particularly in the realm of photocatalytic hydrogen production. Herein, a pioneering exploration involves the loading of PdS and Pt catalyst onto g-C₃N₄ nanosheets to construct g-C₃N₄@PdS@Pt nanocomposites. The photocatalytic activity of nanocomposites was evaluated under visible light and full spectrum irradiation. The results show that g-C₃N₄@PdS@Pt nanocomposites exhibit excellent properties. Under visible light irradiation, these nanocomposites exhibit a remarkable production rate of 1289 μmol·g⁻¹·h⁻¹, marking a staggering 60-fold increase compared to g-C₃N₄@Pt (20.9 μmol·g⁻¹·h⁻¹). Furthermore, when subjected to full spectrum irradiation, the hydrogen production efficiency of g-C₃N₄@PdS@Pt-3 nanocomposites reaches an impressive 11,438 μmol·g⁻¹·h⁻¹, representing an eightfold enhancement compared to g-C₃N₄@Pt (1452 μmol·g⁻¹·h⁻¹) under identical conditions. Detailed investigations into the microstructure and optical properties of g-C₃N₄@PdS catalysts were conducted, shedding light on the mechanisms governing photocatalytic hydrogen production. This study offers valuable insights into the potential of these nanocomposites and their pivotal role in advancing photocatalysis. Full article

(This article belongs to the Special Issue Advances in Composite Photocatalysts)

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16 pages, 4165 KiB

Open AccessArticle

Hybrid Photoelectrocatalytic TiO₂-Co₃O₄/Co(OH)₂ Materials Prepared from Bio-Based Surfactants for Water Splitting

by Fanny Duquet, Valérie Flaud, Christina Villeneuve-Faure, Matthieu Rivallin, Florence Rouessac and Stéphanie Roualdès

Molecules 2023, 28(22), 7599; https://doi.org/10.3390/molecules28227599 - 15 Nov 2023

Cited by 2 | Viewed by 1148

Abstract

The development of new photoanode materials for hydrogen production and water treatment is in full progress. In this context, hybrid TiO₂-Co₃O₄/Co(OH)₂ photoanodes prepared using the sol–gel method using biosurfactants are currently being developed by our group. [...] Read more.

The development of new photoanode materials for hydrogen production and water treatment is in full progress. In this context, hybrid TiO₂-Co₃O₄/Co(OH)₂ photoanodes prepared using the sol–gel method using biosurfactants are currently being developed by our group. The combination of TiO₂ with a cobalt-based compound significantly enhances the visible absorption and electrochemical performance of thin films, which is mainly due to an increase in the specific surface area and a decrease in the charge transfer resistance on the surface of the thin films. The formation of these composites allows for a 30-fold increase in the current density when compared to cobalt-free materials, with the best TiO₂-CoN0.5 sample achieving a current of 1.570 mA.cm⁻² and a theoretical H₂ production rate of 0.3 µmol.min⁻¹.cm⁻² under xenon illumination. Full article

(This article belongs to the Special Issue Advances in Composite Photocatalysts)

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18 pages, 12675 KiB

Open AccessArticle

Selectivity of Sol-Gel and Hydrothermal TiO₂ Nanoparticles towards Photocatalytic Degradation of Cationic and Anionic Dyes

by Md. Torikul Islam, Md. Nahid Parvez Roni, Md. Yunus Ali, Md. Robiul Islam, Md. Shamim Hossan, M. Habibur Rahman, A. A. S. Mostofa Zahid, Md. Nur E Alam, Md. Abu Hanif and M. Shaheer Akhtar

Molecules 2023, 28(19), 6834; https://doi.org/10.3390/molecules28196834 - 27 Sep 2023

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Abstract

Titanium dioxide (TiO₂) nanoparticles have been extensively studied for catalyzing the photo-degradation of organic pollutants, the photocatalyst being nonselective to the substrate. We, however, found that TiO₂ nanoparticles prepared via the sol-gel and hydrothermal synthetic routes each possess a definite [...] Read more.

Titanium dioxide (TiO₂) nanoparticles have been extensively studied for catalyzing the photo-degradation of organic pollutants, the photocatalyst being nonselective to the substrate. We, however, found that TiO₂ nanoparticles prepared via the sol-gel and hydrothermal synthetic routes each possess a definite specificity to the charge of the substrate for photodegradation. The nanoparticles were characterized by SEM, FTIR, XRD, TGA, and UV-visible spectra, and the photocatalytic degradation under UV-B (285 nm) irradiation of two model compounds, anionic methyl Orange (MO) and cationic methylene blue (MB) was monitored by a UV-visible spectrophotometer. Untreated sol-gel TiO₂ nanoparticles (T_sg) preferentially degraded MO over MB (90% versus 40% in two hours), while after calcination at 400 °C for two hours (T_sgc) they showed reversed specificity (50% MO versus 90% MB in one hour). The as-prepared hydrothermal TiO₂ nanoparticles (T_ht) behaved in the opposite sense of T_sg (41% MO versus 91% MB degraded in one and a half hours); calcination at 400 °C (T_htc) did not reverse the trend but enhanced the efficiency of degradation. The study indicates that TiO₂ nanoparticles can be made to degrade a specific class of organic pollutants from an effluent facilitating the recycling of a specific class of pollutants for cost-effective effluent management. Full article

(This article belongs to the Special Issue Advances in Composite Photocatalysts)

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