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Nanostructured Materials for Photocatalysis

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

Deadline for manuscript submissions: closed (28 February 2019) | Viewed by 48617

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Prof. Dr. Paolo Fornasiero

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Department of Chemical and Pharmaceutical Sciences, Universita’degli Studi di Trieste, 34127 Trieste, Italy
Interests: material chemistry; functional metal oxides; hybrids and nanostructured catalysts; energy applications; environmental applications; heterogeneous catalysis
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Prof. Dr. Tiziano Montini

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Department of Chemical and Pharmaceutical Sciences, University of Trieste, via L. Giorgieri 1, 34127 Trieste, Italy
Interests: design of photocatalysts for H₂ production

Dr. Konstantinos Christoforidis

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Department of Environmental Engineering, Democritus University of Thrace, Vasilisis Sofias 12, 67100 Xanthi, Greece
Interests: Design of photoactive multi-phase nanomaterials; development of novel chemical methodologies for nanocatalysts synthesis; photocatalysis for water spitting, CO₂ reduction and pollutants degradation
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

Photocatalysis has been identified as a suitable and sustainable approach to address two of the main issues facing humanity: Environmental protection and clean and sustainable energy production. Many efforts have been dedicated over the past few decades to the realization of efficient semiconductor photocatalysts and understanding the fundamentals governing efficiency. This is because of the advantages of the process operating under ambient conditions and the utilization of clean and endless solar energy. This Special Issue aims at presenting the current scientific developments in the area of photoactive heterojunction nanomaterials and their photocatalytic applications to environmental protection, clean energy production and chemical synthesis/processing. It is open to both original research articles and reviews.

Prof. Dr. Paolo Fornasiero
Prof. Dr. Tiziano Montini
Dr. Konstantinos Christoforidis
Guest Editors

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Keywords

environmental pollution
water and air contamination
hydrogen production
CO₂ reduction
N₂ photoactivation
organic synthesis
reactors and testing methods
reaction kinetics and mechanism
semiconductors
light-matter interaction
computational studies

Published Papers (10 papers)

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Research

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16 pages, 3001 KiB

Open AccessArticle

Exhaustive Photocatalytic Lindane Degradation by Combined Simulated Solar Light-Activated Nanocrystalline TiO₂ and Inorganic Oxidants

by Sanaullah Khan, Changseok Han, Murtaza Sayed, Mohammad Sohail, Safeer Jan, Sabiha Sultana, Hasan M. Khan and Dionysios D. Dionysiou

Catalysts 2019, 9(5), 425; https://doi.org/10.3390/catal9050425 - 07 May 2019

Cited by 26 | Viewed by 4052

Abstract

Organochlorine compounds (OCs) are very toxic, highly persistent, and ubiquitous contaminants in the environment. Degradation of lindane, a selected OC, by simulated solar light-activated TiO₂ (SSLA-TiO₂) photocatalysis was investigated. The film types of the TiO₂ photocatalyst were prepared using a dip-coating method. The physical properties of the films were investigated using X-ray diffraction, transmission electron microscopy, and environmental scanning electron microscopy. The SSLA-TiO₂ photocatalysis led to a lindane removal of 23% in 6 h, with 0.042 h⁻¹ of an observed pseudo first-order rate constant (k_obs). The SSLA-TiO₂ photocatalysis efficiency was greatly enhanced by adding hydrogen peroxide (H₂O₂), persulfate (S₂O₈²⁻), or both combined, corresponding to a 64%, 89%, and 99% lindane removal in the presence of 200 µM of H₂O₂, S₂O₈²⁻, or equimolar H₂O₂-S₂O₈²⁻, respectively. The hydroxyl and sulfate radicals mainly participated in lindane degradation, proven by the results of a radical scavenger study. The degradation kinetics were hindered in the presence of the water constituents, indicated by a 61%, 35%, 50%, 70%, 88%, and 91% degradation of lindane in 6 h, using a SSLA-TiO₂/S₂O₈²⁻/H₂O₂ photocatalysis system containing 1.0 mg L⁻¹ humic acid (HA), or 1 mM of CO₃²⁻, HCO₃⁻, NO₃⁻, SO₄²⁻, and Cl⁻, respectively. The TiO₂ film demonstrated high reusability during four runs of lindane decomposition experiments. The SSLA-TiO₂/S₂O₈²⁻/H₂O₂ photocatalysis is very effective for the elimination of a persistent OC, lindane, from a water environment. Full article

(This article belongs to the Special Issue Nanostructured Materials for Photocatalysis)

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13 pages, 2377 KiB

Open AccessArticle

Hierarchically-Structured TiO₂/MnO₂ Hollow Spheres Exhibiting the Complete Mineralization of Phenol

by Caiguo Jiang, Yi Ge, Wenjing Chen, Li Hua, Huiquan Li, Ying Zhang and Shunsheng Cao

Catalysts 2019, 9(4), 390; https://doi.org/10.3390/catal9040390 - 25 Apr 2019

Cited by 5 | Viewed by 3765

Abstract

Although TiO₂ or MnO₂-based materials have been widely used for the degradation of phenolic compounds, complete mineralization is still a challenge, especially for TiO₂-based materials. Here, we devise a hierarchically-structured TiO₂/MnO₂ (HTM) hollow sphere, in which hollow TiO₂ acts as a skeleton for the deposition of MnO₂ in order to prevent the aggregation of MnO₂ nanoparticles and to maintain its hollow structure. During the oxidation reaction, the as-synthesized HTM can fully exert their respective advantages of the TiO₂ and MnO₂ species to realize the first stage of the rapid oxidation degradation of phenol and the second stage of the complete photo-mineralization of residual phenol and its intermediates, which efficiently overcomes the incomplete mineralization of phenolic compounds. The degradation mechanism and pathway of phenol are also proposed according to the analysis of Mass Spectrometry (MS). Therefore, this work provides a new insight for exploring hierarchically-structured materials with two or more species. Full article

(This article belongs to the Special Issue Nanostructured Materials for Photocatalysis)

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16 pages, 3589 KiB

Open AccessArticle

Radiative and Non-Radiative Recombination Pathways in Mixed-Phase TiO₂ Nanotubes for PEC Water-Splitting

by Rambabu Yalavarthi, Alberto Naldoni, Štěpán Kment, Luca Mascaretti, Hana Kmentová, Ondřej Tomanec, Patrik Schmuki and Radek Zbořil

Catalysts 2019, 9(2), 204; https://doi.org/10.3390/catal9020204 - 23 Feb 2019

Cited by 38 | Viewed by 6535

Abstract

Anatase and rutile mixed-phase TiO₂ with an ideal ratio has been proven to significantly enhance photoelectrochemical (PEC) activity in water-splitting applications due to suppressing the electron–hole recombination. However, the mechanism of this improvement has not been satisfactory described yet. The PEC water oxidation (oxygen evolution) at the interface of TiO₂ photoanode and electrolyte solution is determined by the fraction of the photogenerated holes that reach the solution and it is defined as the hole transfer efficiency. The surface and bulk recombination processes in semiconductor photoanodes majorly influence the hole transfer efficiency. In this work, we study the hole transfer process involved in mixed-phase TiO₂ nanotube arrays/solution junction using intensity-modulated photocurrent and photovoltage spectroscopy (IMPS and IMVS); then, we correlate the obtained hole transfer rate constants to (photo)electrochemical impedance spectroscopy (PEIS) measurements. The results suggest that the enhanced performance of the TiO₂ mixed-phase is due to the improved hole transfer rate across the TiO₂/liquid interface as well as to the decrease in the surface trap recombination of the holes. Full article

(This article belongs to the Special Issue Nanostructured Materials for Photocatalysis)

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27 pages, 10021 KiB

Open AccessArticle

Strong Photo-Oxidative Capability of ZnWO₄ Nanoplates with Highly Exposed {0 1 1} Facets

by Bao-gai Zhai, Long Yang, Fu-fang Zhou, Jun-sheng Shi and Yuan Ming Huang

Catalysts 2019, 9(2), 178; https://doi.org/10.3390/catal9020178 - 14 Feb 2019

Cited by 18 | Viewed by 3220

Abstract

ZnWO₄ nanoplates with highly exposed {0

\bar{1}

ZnWO₄ nanoplates with highly exposed {0

\bar{1}

1} facets were synthesized via a hydrothermal technique. The phase, morphology, and optical characteristics of ZnWO₄ nanoplates were characterized with scanning electron microscopy, transmission electron microscopy, X–ray diffraction, diffuse ultraviolet–visible light (UV–Vis) reflectance spectroscopy, photoluminescence (PL) spectrophotometry, and PL lifetime spectroscopy. Optical characterizations, along with the density functional calculations, confirm that the strong blue PL band of ZnWO₄ nanoplates originates from the intrinsic defects in ZnWO₄ nanoplates. Furthermore, photocatalytic tests show that ZnWO₄ nanoplates exhibit strong photo-oxidative capability of complete mineralization of the organic pollutant (methyl orange) in water, whereas ZnWO₄ nanoparticles can only cleave the organic molecules into fragments. The superior photo-oxidative capability of ZnWO₄ nanoplates can be attributed to the specific chemical bonding and stereochemistry on the exposed facets. This work demonstrates that crystal facet engineering is an efficient strategy to endow ZnWO₄ with strong photo-oxidative capability. Full article

(This article belongs to the Special Issue Nanostructured Materials for Photocatalysis)

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12 pages, 5056 KiB

Open AccessArticle

N-Doped K₃Ti₅NbO₁₄@TiO₂ Core-Shell Structure for Enhanced Visible-Light-Driven Photocatalytic Activity in Environmental Remediation

by Xin Gao, Chen Wang, Qixiang Xu, Hongjie Lv, Ting Chen, Chao Liu and Xinguo Xi

Catalysts 2019, 9(1), 106; https://doi.org/10.3390/catal9010106 - 21 Jan 2019

Cited by 1 | Viewed by 4485

Abstract

A novel N-doped K₃Ti₅NbO₁₄@TiO₂ (NTNT) core-shell heterojunction photocatalyst was synthesized by firstly mixing titanium isopropoxide and K₃Ti₅NbO₁₄ nanobelt, and then calcinating at 500 °C in air using urea as the nitrogen source. The samples were analyzed by X-ray diffraction pattern (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), UV-Vis absorption spectroscopy and X-ray photoelectron spectroscopic (XPS) spectra. Anatase TiO₂ nanoparticles were closely deposited on the surface of K₃Ti₅NbO₁₄ nanobelt to form a nanoscale heterojunction structure favorable for the separation of photogenerated charge carriers. Meanwhile, the nitrogen atoms were mainly doped in the crystal lattices of TiO₂, resulting in the increased light harvesting ability to visible light region. The photocatalytic performance was evaluated by the degradation of methylene blue (MB) under visible light irradiation. The enhanced photocatalytic activity of NTNT was ascribed to the combined effects of morphology engineering, N doping and the formation of heterojunction. A possible photocatalytic mechanism was proposed based on the experimental results. Full article

(This article belongs to the Special Issue Nanostructured Materials for Photocatalysis)

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13 pages, 5212 KiB

Open AccessArticle

Microcystis aeruginosa Synergistically Facilitate the Photocatalytic Degradation of Tetracycline Hydrochloride and Cr(VI) on PAN/TiO₂/Ag Nanofiber Mats

by Lei Wang, Changbo Zhang, Rong Cheng, Jafar Ali, Zhenbo Wang, Gilles Mailhot and Gang Pan

Catalysts 2018, 8(12), 628; https://doi.org/10.3390/catal8120628 - 05 Dec 2018

Cited by 17 | Viewed by 3627

Abstract

Cyanobacterial blooms can cause serious damage to aquatic ecosystems. However, we have demonstrated that typical algae-blooming species Microcystis aeruginosa (M. aeruginosa) combined with photocatalysts could synergistically facilitate the photodecontamination of tetracycline hydrochloride (TC) and Cr(VI). In this study, for the first time, harmful algae were successfully converted into photoreactive bionano hybrid materials by immobilizing M. aeruginosa cells onto polyacrylonitrile (PAN)-TiO₂/Ag hybrid nanofibers, and their photocatalytic activity was evaluated. The addition of M. aeruginosa significantly improved the photodecontamination, and the reaction rate constant (k) values of TC and Cr(VI) degradation by M. aeruginosa-PAN/TiO₂/Ag nanofiber mats were 2.4 and 1.5-fold higher than that of bare PAN/TiO₂/Ag nanofiber. Photoreaction caused damage to algae cells, but no microcystin was found that had been photodegraded simultaneously. The effects of various active species were also investigated, and the photodegradation mechanism was proposed. Recycling tests revealed that this flexible M. aeruginosa-PAN/TiO₂/Ag hybrid mat had potential application in the removal of mixed organic and inorganic pollutants with high efficiency and without secondary pollutants. Thus, harmful algae blooms could serve as an efficient materials to remove toxic pollutants in a sustainable way under visible light irradiation. Full article

(This article belongs to the Special Issue Nanostructured Materials for Photocatalysis)

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12 pages, 11630 KiB

Open AccessArticle

Full-Spectrum Photocatalytic Activity of ZnO/CuO/ZnFe₂O₄ Nanocomposite as a PhotoFenton-Like Catalyst

by Zhenzhen Li, Huabin Chen and Wenxia Liu

Catalysts 2018, 8(11), 557; https://doi.org/10.3390/catal8110557 - 18 Nov 2018

Cited by 41 | Viewed by 6973

Abstract

Deriving photocatalysts by the calcination of hydrotalcite-like compounds has attracted growing interest for extending their photocatalytic activity to the visible and even near-infrared (NIR) light regions. Herein, we describe the acquisition of a ZnO/CuO/ZnFe₂O₄ nanocomposite with good photoFenton-like catalytic activity under UV, visible and near-infrared (NIR) light irradiation by optimizing the calcination temperature of the coprecipitation product of Zn²⁺, Cu²⁺ and Fe³⁺. The ZnO/CuO/ZnFe₂O₄ nanocomposite is composed of symbiotic crystals of ZnO, CuO and ZnFe₂O₄, which enable the nanocomposite to show absorption in the UV, visible and NIR light regions and to produce a transient photocurrent in the presence of H₂O₂ under NIR irradiation. The full-spectrum photoFenton-like catalyst shows improved performance for the degradation of methyl orange with an increasing amount of H₂O₂ and is very stable in the recycling process. We believe that the ZnO/CuO/ZnFe₂O₄ nanocomposite is a promising full-spectrum photoFenton-like catalyst for the degradation of organic pollutants. Full article

(This article belongs to the Special Issue Nanostructured Materials for Photocatalysis)

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13 pages, 1854 KiB

Open AccessCommunication

Enhancement Photocatalytic Activity of the Heterojunction of Two-Dimensional Hybrid Semiconductors ZnO/V₂O₅

by Juan Aliaga, Nasla Cifuentes, Guillermo González, Clivia Sotomayor-Torres and Eglantina Benavente

Catalysts 2018, 8(9), 374; https://doi.org/10.3390/catal8090374 - 04 Sep 2018

Cited by 66 | Viewed by 5296

Abstract

In this work, we report the fabrication of the new heterojunction of two 2D hybrid layered semiconductors—ZnO (stearic acid)/V₂O₅ (hexadecylamine)—and its behavior in the degradation of aqueous methylene blue under visible light irradiation. The optimal photocatalyst efficiency, reached at a ZnO (stearic acid)/V₂O₅ (hexadecylamine) ratio of 1:0.25, results in being six times higher than that of pristine zinc oxide. Reusability test shows that after three photocatalysis cycles, no significant changes in either the dye degradation efficiency loss, nor the photocatalyst structure, occur. Visible light photocatalytic performance observed indicates there is synergetic effect between both 2D nanocomposites used in the heterojunction. The visible light absorption enhancement promoted by the narrower bandgap V₂O₅ based components; an increased photo generated charge separation favored by extensive interface area; and abundance of hydrophobic sites for dye adsorption appear as probable causes of the improved photocatalytic efficiency in this hybrid semiconductors heterojunction. Estimated band-edge positions for both conduction and valence band of semiconductors, together with experiments using specific radical scavengers, allow a plausible photodegradation mechanism. Full article

(This article belongs to the Special Issue Nanostructured Materials for Photocatalysis)

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15 pages, 17149 KiB

Open AccessArticle

Pyrene-Based Conjugated Polymer/Bi₂MoO₆ Z-Scheme Hybrids: Facile Construction and Sustainable Enhanced Photocatalytic Performance in Ciprofloxacin and Cr(VI) Removal under Visible Light Irradiation

by Xianglong Yang, Yonggang Xiang, Xuepeng Wang, Shu Li, Hao Chen and Xing Ding

Catalysts 2018, 8(5), 185; https://doi.org/10.3390/catal8050185 - 01 May 2018

Cited by 9 | Viewed by 4089

Abstract

The search for appropriate materials with favorable staggered energy band arrangements is important and is a great challenge in order to fabricate Z-scheme photocatalysts with high activity in visible light. In this study, we demonstrated a facile and feasible strategy to construct highly active organic–inorganic Z-scheme hybrids (P-BMO) with linear pyrene-based conjugated polymer (P17-E) and Bi₂MoO₆, via an in-situ palladium-catalyzed cross-coupling reaction. The characterization results revealed C-O chemical bond formed at the heterointerface between P17-E and Bi₂MoO₆ after in-situ polycondensation and endowed the hybrids with observably improved photogenerated carries transfer capabilities. Visible, light-driven photocatalytic removal of ciprofloxacin and Cr(VI) were significantly enhanced after the incorporation of P17-E into Bi₂MoO₆, whether with the morphology of nanosheets, nanobelts, or microspheres. Moreover, these P-BMO hybrids were also found to exhibit excellent sustainable photocatalytic performance after four runs of photocatalytic evaluation tests, suggesting their high activity and stability. To better eliminate the redox ability enhancement of P-BMO, a reasonable Z-scheme electrons transferring mechanism between P17-E and Bi₂MoO₆ was proposed and proved by the determination of •O₂^– and •OH and Pt nanoparticles photodeposition experiments. This work might provide a viable source and insight into the design of Z-scheme photocatalysts with excellent redox ability for environmental remediation. Full article

(This article belongs to the Special Issue Nanostructured Materials for Photocatalysis)

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Review

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15 pages, 3446 KiB

Open AccessReview

Recent Progress in Constructing Plasmonic Metal/Semiconductor Hetero-Nanostructures for Improved Photocatalysis

by Liang Ma, Shuang Chen, Yun Shao, You-Long Chen, Mo-Xi Liu, Hai-Xia Li, Yi-Ling Mao and Si-Jing Ding

Catalysts 2018, 8(12), 634; https://doi.org/10.3390/catal8120634 - 07 Dec 2018

Cited by 18 | Viewed by 5364

Abstract

Hetero-nanomaterials constructed by plasmonic metals and functional semiconductors show enormous potential in photocatalytic applications, such as in hydrogen production, CO₂ reduction, and treatment of pollutants. Their photocatalytic performances can be better regulated through adjusting structure, composition, and components’ arrangement. Therefore, the reasonable design and synthesis of metal/semiconductor hetero-nanostructures is of vital significance. In this mini-review, we laconically summarize the recent progress in efficiently establishing metal/semiconductor nanomaterials for improved photocatalysis. The defined photocatalysts mainly include traditional binary hybrids, ternary multi-metals/semiconductor, and metal/multi-semiconductors heterojunctions. The underlying physical mechanism for the enhanced photocatalysis of the established photocatalysts is highlighted. In the end, a brief summary and possible future perspectives for further development in this field are demonstrated. Full article

(This article belongs to the Special Issue Nanostructured Materials for Photocatalysis)

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