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Heterojunction-Based Photocatalysts and Photoelectrodes for Water Splitting and CO2...
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Heterojunction-Based Photocatalysts and Photoelectrodes for Water Splitting and CO2 Reduction: From Fundamentals to Applications

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

Deadline for manuscript submissions: closed (31 December 2020) | Viewed by 24421

Special Issue Editors

Dr. Marco Altomare

E-Mail Website
Guest Editor
Department of Materials Science and Engineering, WW4-LKO, University of Erlangen-Nuremberg, Martensstrasse 7, 91058 Erlangen, Germany
Interests: photocatalysis; photoelectrochemistry; hydrogen generation; self-organizing electrochemistry; electrochemical anodization; TiO2 nanotubes; one-dimensional nanostructures; metal oxide semiconductors; solid state dewetting; metal nanoparticles
Dr. Roland Marschall

E-Mail Website
Co-Guest Editor
Institute of Physical Chemistry, Justus-Liebig-University Giessen, Giessen, Germany
Interests: materials science; mesoporous materials; photocatalysis; water splitting; proton conduction
Prof. Dr. Hicham Idriss

E-Mail Website
Co-Guest Editor
1. SABIC-CRD, King Abdullah University of Science and Technology (KAUST), Thuwal 23955-6900, Saudi Arabia
2. Department of Chemistry, University College London, London WC1H 0AJ, UK
Interests: catalysis; surface science; metal oxides; photo-catalysis; electron transfer; reaction mechanism

Special Issue Information

Dear Colleagues,

Photocatalytic and photoelectrochemical processes have been intensively studied for almost 50 years, and the scientific interest in these areas is still growing. The main reason is the great potential to enable, ideally under solar illumination, a variety of reactions of environmental relevance in the current energy scenario, such as the generation of H2 by water splitting and the reduction of greenhouse gas CO2 to hydrocarbons. Key elements towards high reaction yields are efficient separation and swift transfer of photo-generated charge carriers to reactants. For this, numerous materials have been explored, often in the form of nanostructured semiconductor and metal composites.

The aim of this Special Issue is to highlight current research on heterojunction-based photocatalysts and photoelectrodes for H2 generation and CO2 reduction, with focus on issues that still drastically hamper their performance. In this context, significant advancement lies in further understanding of aspects related to surface structural requirements and their relationship to bulk properties. The electronic properties of, e.g., semiconductor/semiconductor or metal/semiconductor interfaces, the role of metal and metal oxides clusters in charge transfer or, at a more fundamental level, the engineering of orbital overlap between reactants and the semiconductor surfaces, and the associated charge lifetime and charge transfer reaction kinetics are deemed essential to improve photocatalytic and photoelectrochemical efficiencies.

In addition, the development of advanced nanostructuring tools that enable precise morphological control over heterojunction formation is also of crucial importance to maximize light harvesting, for instance by the design of photonic band gap and plasmonic materials, and metamaterials. Additionally, site-specific cocatalyst placement at the semiconductor surface and surface-structure electronic effects on charge transfer (such as changes in work function and electric field) are important parameters requiring further attention.

These are some of the key concepts and topics within the scope of this Special Issue, which is open to original research articles, and also to reviews that target a critical viewpoint in the field.

Dr. Marco Altomare
Dr. Roland Marschall
Prof. Dr. Hicham Idriss
Guest Editors

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Catalysts is an international peer-reviewed open access monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2700 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • photocatalysis
  • photoelectrochemistry
  • water splitting
  • H2 generation
  • CO2 reduction
  • hydrocarbon synthesis
  • semiconductor
  • cocatalyst
  • heterojunction
  • metal cluster
  • metal oxide
  • work function
  • electric field effect
  • plasmonic material
  • photonic band gap
  • charge transfer
  • transient absorption spectroscopy

Published Papers (6 papers)

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Research

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12 pages, 2796 KiB  
Article
Effect of Ag2S Nanocrystals/Reduced Graphene Oxide Interface on Hydrogen Evolution Reaction
by Chen Zhao, Zhi Yu, Jun Xing, Yuting Zou, Huiwen Liu, Hao Zhang, Weili Yu, Hicham Idriss and Chunlei Guo
Catalysts 2020, 10(9), 948; https://doi.org/10.3390/catal10090948 - 19 Aug 2020
Cited by 15 | Viewed by 3937
Abstract
The development of efficient electrocatalyst to produce molecular hydrogen from water is receiving considerable attention, in an effort to decrease our reliance on fossil fuels. The prevention of the aggregation of active sites during material synthesis, in order to increase charge transport properties [...] Read more.
The development of efficient electrocatalyst to produce molecular hydrogen from water is receiving considerable attention, in an effort to decrease our reliance on fossil fuels. The prevention of the aggregation of active sites during material synthesis, in order to increase charge transport properties of electrocatalysts, is needed. We have designed, synthesized, and studied a Ag2S/reduced graphene oxide (rGO) electrochemical catalyst (for hydrogen evolution) from water. The Ag2S nanocrystals were synthesized by the solvothermal method in which the rGO was added. The addition of the rGO resulted in the formation of smaller Ag2S nanocrystals, which consequently increased the electrical conductivity of the composite catalyst. The composite catalyst showed a higher electrochemical catalytic activity than the one with an absence of rGO. At a current density of 10 mA/cm2, a low overpotential of 120 mV was obtained. A Tafel slope of 49.1 mV/dec suggests a Volmer–Herovsky mechanism for the composite catalyst. These results may provide a novel strategy for developing hydrogen evolution reaction (HER) electrocatalysts, via the combining of a nano-semiconductor catalyst with a 2D material. Full article
(This article belongs to the Special Issue Heterojunction-Based Photocatalysts and Photoelectrodes for Water Splitting and CO2 Reduction: From Fundamentals to Applications)
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15 pages, 4687 KiB  
Article
Multi-Leg TiO2 Nanotube Photoelectrodes Modified by Platinized Cyanographene with Enhanced Photoelectrochemical Performance
by Mahdi Shahrezaei, Seyyed Mohammad Hossein Hejazi, Yalavarthi Rambabu, Miroslav Vavrecka, Aristides Bakandritsos, Selda Oezkan, Radek Zboril, Patrik Schmuki, Alberto Naldoni and Stepan Kment
Catalysts 2020, 10(6), 717; https://doi.org/10.3390/catal10060717 - 26 Jun 2020
Cited by 10 | Viewed by 3186
Abstract
Highly ordered multi-leg TiO2 nanotubes (MLTNTs) functionalized with platinized cyanographene are proposed as a hybrid photoelectrode for enhanced photoelectrochemical water splitting. The platinized cyanographene and cyanographene/MLTNTs composite yielded photocurrent densities 1.66 and 1.25 times higher than those of the pristine MLTNTs nanotubes, [...] Read more.
Highly ordered multi-leg TiO2 nanotubes (MLTNTs) functionalized with platinized cyanographene are proposed as a hybrid photoelectrode for enhanced photoelectrochemical water splitting. The platinized cyanographene and cyanographene/MLTNTs composite yielded photocurrent densities 1.66 and 1.25 times higher than those of the pristine MLTNTs nanotubes, respectively. Open circuit VOC decay (VOCD), electrochemical impedance spectroscopy (EIS), and intensity-modulated photocurrent spectroscopy (IMPS) analyses were performed to study the recombination rate, charge transfer characteristics, and transfer time of photogenerated electrons, respectively. According to the VOCD and IMPS results, the addition of (platinized) cynographene decreased the recombination rate and the transfer time of photogenerated electrons by one order of magnitude. Furthermore, EIS results showed that the (platinized) cyanographene MLTNTs composite has the lowest charge transfer resistance and therefore the highest photoelectrochemical performance. Full article
(This article belongs to the Special Issue Heterojunction-Based Photocatalysts and Photoelectrodes for Water Splitting and CO2 Reduction: From Fundamentals to Applications)
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10 pages, 1553 KiB  
Article
Understanding the Photo- and Electro-Carboxylation of o-Methylbenzophenone with Carbon Dioxide
by Keyi Tian, Ruonan Chen, Jiafang Xu, Ge Yang, Xintong Xu and Yanhua Zhang
Catalysts 2020, 10(6), 664; https://doi.org/10.3390/catal10060664 - 12 Jun 2020
Cited by 5 | Viewed by 2845
Abstract
The lack of understanding of the radical reaction mechanism of Carbon dioxide (CO2) in photo- and electro-catalysis results in the development of such applications far behind the traditional synthesis methods. Using methylbenzophenone as the model, we clarify and compare the photo-enolization/Diels−Alder [...] Read more.
The lack of understanding of the radical reaction mechanism of Carbon dioxide (CO2) in photo- and electro-catalysis results in the development of such applications far behind the traditional synthesis methods. Using methylbenzophenone as the model, we clarify and compare the photo-enolization/Diels−Alder (PEDA) mechanism for photo-carboxylation and the two-step single-electron reduction pathway for electro-carboxylation with CO2 through careful control experiments. The regioselective carboxylation products, o-acylphenylacetic acid and α-hydroxycarboxylic acid are obtained, respectively, in photo- and electro-chemistry systems. On the basis of understanding the mechanism, a one-pot step-by-step dicarboxylation of o-methylbenzophenone is designed and conducted. Both the experimental results and related density functional theory (DFT) calculation verify the feasibility of the possible pathway in which electro-carboxylation is conducted right after photo-carboxylation in one vessel. This synthesis approach may provide a mild, eco-friendly strategy for the production of polycarboxylic acids in industry. Full article
(This article belongs to the Special Issue Heterojunction-Based Photocatalysts and Photoelectrodes for Water Splitting and CO2 Reduction: From Fundamentals to Applications)
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13 pages, 3474 KiB  
Article
Crystal-Plane Dependence of Nb-Doped Rutile TiO2 Single Crystals on Photoelectrochemical Water Splitting
by Tomohiko Nakajima, Takako Nakamura and Tetsuo Tsuchiya
Catalysts 2019, 9(9), 725; https://doi.org/10.3390/catal9090725 - 28 Aug 2019
Cited by 4 | Viewed by 3497
Abstract
The crystal-plane dependence of the photoelectrochemical (PEC) water-splitting property of rutile-structured Nb-doped TiO2 (TiO2:Nb) single-crystal substrates was investigated. Among the crystal planes, the (001) plane was a very promising surface for attaining good photocurrent. Under 1 sun illumination at 1.5 [...] Read more.
The crystal-plane dependence of the photoelectrochemical (PEC) water-splitting property of rutile-structured Nb-doped TiO2 (TiO2:Nb) single-crystal substrates was investigated. Among the crystal planes, the (001) plane was a very promising surface for attaining good photocurrent. Under 1 sun illumination at 1.5 V vs. a reversible hydrogen electrode, the TiO2:Nb(001) single-crystal substrate showed the highest photocurrent (0.47 mA/cm2) among the investigated substrates. The doped Nb ions were segregated inward from the top surface, and the TiO2 ultrathin layer was formed at the surface of the crystal, resulting in the formation of a heterointerface between the TiO2 and the TiO2:Nb. The enhancement of the PEC properties of the TiO2:Nb(001) single-crystal substrate originated from favorable atomic configurations for water molecule absorption and facilitation of transport of photoexcited electron–hole pairs in the depletion layer formed around the heterointerface of TiO2 thin layers on the base crystal. Full article
(This article belongs to the Special Issue Heterojunction-Based Photocatalysts and Photoelectrodes for Water Splitting and CO2 Reduction: From Fundamentals to Applications)
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11 pages, 3261 KiB  
Article
Structure and Photocatalytic Activity of PdCrOx Cocatalyst on SrTiO3 for Overall Water Splitting
by Tomoki Kanazawa, Shunsuke Nozawa, Daling Lu and Kazuhiko Maeda
Catalysts 2019, 9(1), 59; https://doi.org/10.3390/catal9010059 - 08 Jan 2019
Cited by 23 | Viewed by 3654
Abstract
The mechanism of PdCrOx multi-component cocatalyst formation on SrTiO3 was investigated using transmission electron microscopy, X-ray absorption fine structure spectroscopy and X-ray photoelectron spectroscopy. The PdCrOx/SrTiO3 samples were synthesized by a photodeposition method under UV light irradiation ( [...] Read more.
The mechanism of PdCrOx multi-component cocatalyst formation on SrTiO3 was investigated using transmission electron microscopy, X-ray absorption fine structure spectroscopy and X-ray photoelectron spectroscopy. The PdCrOx/SrTiO3 samples were synthesized by a photodeposition method under UV light irradiation (λ > 300 nm) for various time periods (0–5 h). The fine structure and valence state of the Pd species of PdCrOx nanoparticles were varied from Pd oxide to a mixture of metallic Pd and oxidized Pd species with an increase in the irradiation time. The overall water-splitting activity of PdCrOx was strongly dependent on the photoirradiation time during deposition. Although longer photoirradiation time during preparation did not influence the H2 evolution activity of PdCrOx/SrTiO3 from aqueous methanol solution, it was effective in suppressing the O2 photoreduction activity, which is one of the backward reactions during overall water splitting. Full article
(This article belongs to the Special Issue Heterojunction-Based Photocatalysts and Photoelectrodes for Water Splitting and CO2 Reduction: From Fundamentals to Applications)
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Review

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25 pages, 3009 KiB  
Review
An Overview of the Photocatalytic Water Splitting over Suspended Particles
by Muhammad Amtiaz Nadeem, Mohd Adnan Khan, Ahmed Abdeslam Ziani and Hicham Idriss
Catalysts 2021, 11(1), 60; https://doi.org/10.3390/catal11010060 - 04 Jan 2021
Cited by 37 | Viewed by 6622
Abstract
The conversion of solar to chemical energy is one of the central processes considered in the emerging renewable energy economy. Hydrogen production from water splitting over particulate semiconductor catalysts has often been proposed as a simple and a cost-effective method for large-scale production. [...] Read more.
The conversion of solar to chemical energy is one of the central processes considered in the emerging renewable energy economy. Hydrogen production from water splitting over particulate semiconductor catalysts has often been proposed as a simple and a cost-effective method for large-scale production. In this review, we summarize the basic concepts of the overall water splitting (in the absence of sacrificial agents) using particulate photocatalysts, with a focus on their synthetic methods and the role of the so-called “co-catalysts”. Then, a focus is then given on improving light absorption in which the Z-scheme concept and the overall system efficiency are discussed. A section on reactor design and cost of the overall technology is given, where the possibility of the different technologies to be deployed at a commercial scale and the considerable challenges ahead are discussed. To date, the highest reported efficiency of any of these systems is at least one order of magnitude lower than that deserving consideration for practical applications. Full article
(This article belongs to the Special Issue Heterojunction-Based Photocatalysts and Photoelectrodes for Water Splitting and CO2 Reduction: From Fundamentals to Applications)
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