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2D Energy Materials

A special issue of Energies (ISSN 1996-1073). This special issue belongs to the section "D1: Advanced Energy Materials".

Deadline for manuscript submissions: closed (20 December 2019) | Viewed by 17733

Special Issue Editors


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Guest Editor
Department of Materials Science and Engineering, Seoul National University, Seoul 08826, Korea
Interests: chemical sensors for e-nose and e-tongue; memristors; plasmonics; metal–insulator transition; and ferroelectricity
Special Issues, Collections and Topics in MDPI journals
Department of Materials Science and Engineering & Department of Energy Systems Research, Ajou University, Suwon 16499, Korea
Interests: mateirlas growth; low dimenstional materials; x-ray diffraction; physical chemistry

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Guest Editor
Department of Materials Science and Engineering, Dankook University, Cheonan 31116, Korea
Interests: 2D materials; fuel cell materials; ionic and electronic conductors

Special Issue Information

Dear Colleagues,

Two-dimensional (2D) materials represent a fast-growing class of materials. After the discovery of atomically thin graphene exfoliated from graphite, 2D materials have undergone rapid development for applications of their unusual electronic, mechanical, chemical, electrochemical, and optical properties. The unique bonding nature of strong in-plane chemical bonding and weak out-of-plane van der Waals interactions allows for the manipulation of the interlayer spacing and surface functional groups through effective nanoscale surface/interficial engineering, resulting in many 2D materials of large in-plane topology and atomic scale thickness. Extensive studies have been carried out on 2D materials with diversified applications, including electronics, sensing, catalysis, energy storage, and energy conversion, etc. In light of the ever-growing demand for electricity storage in stationary and mobile electronic devices and for energy conversion on large and small scales, atomically thin layered structures of electrochemically active 2D materials are considered very attractive for energy storage devices, and those of highly transparent and (semi-)conducting 2D materials for energy conversion devices. Typical 2D materials for energy storage and conversion include graphene, transition metal dichalcogenides, transition metal oxides/hydroxides, transition metal carbides/nitrides (MXenes), and 2D metal–organic frameworks and covalent–organic frameworks. This Special Issue focuses on the synthesis and applications of 2D materials for energy storage and conversion devices.

We cordially invite you to submit manuscripts on all related topics for this Special Issue "2D Energy Materials”. Both theoretical and experimental contributions are welcome.

Prof. Dr. Ho Won Jang
Dr. Hak Ki Yu
Prof. Dr. Hee Jung Park
Guest Editor

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. Energies is an international peer-reviewed open access semimonthly 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 2600 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

  • 2D materials for energy storage and conversion
  • Graphene, transition metal dichalcogenides/oxides/hydroxides/carbides/nitrides, Mxenes, 2D metal–organic frameworks
  • Batteries
  • Supercapacitors
  • Solar cells
  • Fuel cells
  • Water splitting
  • CO2 reduction
  • Thermoelectric
  • Energy harvesting.

Published Papers (5 papers)

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Research

11 pages, 3030 KiB  
Article
Effect of UV-Light Treatment on Efficiency of Perovskite Solar Cells (PSCs)
by Sangmo Kim, Hoang Van Quy, Hyung Wook Choi and Chung Wung Bark
Energies 2020, 13(5), 1069; https://doi.org/10.3390/en13051069 - 01 Mar 2020
Cited by 6 | Viewed by 3785
Abstract
We employed ultra-violet (UV) light treatment on the TiO2 layer prior to coating the perovskite layer to improve the solar conversion efficiency of perovskite solar cells (PSCs). A laboratory-made UV treatment system was equipped with various UV light sources (8 W power; [...] Read more.
We employed ultra-violet (UV) light treatment on the TiO2 layer prior to coating the perovskite layer to improve the solar conversion efficiency of perovskite solar cells (PSCs). A laboratory-made UV treatment system was equipped with various UV light sources (8 W power; maximum wavelengths of 254, 302, and 365 nm). The UV light treatment improved the power conversion efficiency (PCE) while coating the uniformity layer and removing impurities from the surface of cells. After the PSCs were exposed to UV light, their PCE developed approximately 10% efficiency; PBI2 decreased without changing the structure. Full article
(This article belongs to the Special Issue 2D Energy Materials)
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12 pages, 4697 KiB  
Article
Influence of C3N4 Precursors on Photoelectrochemical Behavior of TiO2/C3N4 Photoanode for Solar Water Oxidation
by Swetha S. M. Bhat, Sang Eon Jun, Sol A Lee, Tae Hyung Lee and Ho Won Jang
Energies 2020, 13(4), 974; https://doi.org/10.3390/en13040974 - 21 Feb 2020
Cited by 18 | Viewed by 4027
Abstract
Photoelectrochemical water splitting is considered as a long-term solution for the ever-increasing energy demands. Various strategies have been employed to improve the traditional TiO2 photoanode. In this study, TiO2 nanorods were decorated by graphitic carbon nitride (C3N4) [...] Read more.
Photoelectrochemical water splitting is considered as a long-term solution for the ever-increasing energy demands. Various strategies have been employed to improve the traditional TiO2 photoanode. In this study, TiO2 nanorods were decorated by graphitic carbon nitride (C3N4) derived from different precursors such as thiourea, melamine, and a mixture of thiourea and melamine. Photoelectrochemical activity of TiO2/C3N4 photoanode can be modified by tuning the number of precursors used to synthesize C3N4. C3N4 derived from the mixture of melamine and thiourea in TiO2/C3N4 photoanode showed photocurrent density as high as 2.74 mA/cm2 at 1.23 V vs. RHE. C3N4 synthesized by thiourea showed particle-like morphology, while melamine and melamine with thiourea derived C3N4 yielded two dimensional (2D) nanosheets. Nanosheet-like C3N4 showed higher photoelectrochemical performance than that of particle-like nanostructures as specific surface area, and the redox ability of nanosheets are believed to be superior to particle-like nanostructures. TiO2/C3N4 displayed excellent photostability up to 20 h under continuous illumination. Thiourea plays an important role in enhancing the photoelectrochemical performance of TiO2/C3N4. This study emphasizes the fact that the improved photoelectrochemical performance can be achieved by varying the precursors of C3N4 in TiO2/C3N4 heterojunction. This is the first report to show the influence of C3N4 precursors on photoelectrochemical performance in TiO2/C3N4 systems. This would pave the way to explore different precursors influence on C3N4 with respect to the photoelectrochemical response of TiO2/C3N4 heterojunction photoanode. Full article
(This article belongs to the Special Issue 2D Energy Materials)
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10 pages, 4622 KiB  
Article
Biomass-Derived Graphitic Carbon Encapsulated Fe/Fe3C Composite as an Anode Material for High-Performance Lithium Ion Batteries
by Ying Liu, Xueying Li, Anupriya K. Haridas, Yuanzheng Sun, Jungwon Heo, Jou-Hyeon Ahn and Younki Lee
Energies 2020, 13(4), 827; https://doi.org/10.3390/en13040827 - 14 Feb 2020
Cited by 25 | Viewed by 2822
Abstract
Lithium ion (Li-ion) batteries have been widely applied to portable electronic devices and hybrid vehicles. In order to further enhance performance, the search for advanced anode materials to meet the growing demand for high-performance Li-ion batteries is significant. Fe3C as an [...] Read more.
Lithium ion (Li-ion) batteries have been widely applied to portable electronic devices and hybrid vehicles. In order to further enhance performance, the search for advanced anode materials to meet the growing demand for high-performance Li-ion batteries is significant. Fe3C as an anode material can contribute more capacity than its theoretical one due to the pseudocapacity on the interface. However, the traditional synthetic methods need harsh conditions, such as high temperature and hazardous and expensive chemical precursors. In this study, a graphitic carbon encapsulated Fe/Fe3C (denoted as Fe/Fe3C@GC) composite was synthesized as an anode active material for high-performance lithium ion batteries by a simple and cost-effective approach through co-pyrolysis of biomass and iron precursor. The graphitic carbon shell formed by the carbonization of sawdust can improve the electrical conductivity and accommodate volume expansion during discharging. The porous microstructure of the shell can also provide increased active sites for the redox reactions. The in-situ-formed Fe/Fe3C nanoparticles show pseudocapacitive behavior that increases the capacity. The composite exhibits a high reversible capacity and excellent rate performance. The composite delivered a high initial discharge capacity of 1027 mAh g−1 at 45 mA g−1 and maintained a reversible capacity of 302 mAh g−1 at 200 mA g−1 after 200 cycles. Even at the high current density of 5000 mA g−1, the Fe/Fe3C@GC cell also shows a stable cycling performance. Therefore, Fe/Fe3C@GC composite is considered as one of the potential anode materials for lithium ion batteries. Full article
(This article belongs to the Special Issue 2D Energy Materials)
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10 pages, 3720 KiB  
Article
Effect of Surface Treatment by Chemical-Mechanical Polishing for Transparent Electrode of Perovskite Solar Cells
by Sangmo Kim and Chung Wung Bark
Energies 2020, 13(3), 585; https://doi.org/10.3390/en13030585 - 27 Jan 2020
Cited by 6 | Viewed by 3808
Abstract
Perovskite solar cells (PSCs) are usually fabricated by using the spin coating method. During the fabrication process, the surface status is very important for energy conversion between layers coated in the substrate. PSCs have multilayer-stacked structures, such as the transparent electrode layer, the [...] Read more.
Perovskite solar cells (PSCs) are usually fabricated by using the spin coating method. During the fabrication process, the surface status is very important for energy conversion between layers coated in the substrate. PSCs have multilayer-stacked structures, such as the transparent electrode layer, the perovskite layer, and a metal electrode. The efficiency and uniformity of all layers depend on the surface status of the transparent electrode coated on the glass substrate. Until now, etching methods by chemical processes have been introduced to make the substrate surface smooth and uniform by decreasing surface roughness. However, highly reactive chemical treatments can be harmful to the environment. In this study, we employed an eco-friendly chemical-mechanical polishing (CMP) process to ensure the fluorine-doped tin oxide (FTO) substrate is treated with a smooth surface. Before the perovskite layer and electron transport layer (ETL) are applied, the TiO2 layer is coated with the FTO substrate, and the surface of the FTO substrate is polished using CMP. As a result, the CMP-treated surface of the FTO substrate showed a smooth surface, and the PSCs with CMP treatment did not require conventional TiCl4 treatment. Full article
(This article belongs to the Special Issue 2D Energy Materials)
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8 pages, 2751 KiB  
Article
Reduced Bipolar Conduction in Bandgap-Engineered n-Type Cu0.008Bi2(Te,Se)3 by Sulfur Doping
by Weon Ho Shin, Hyun-Sik Kim, Se Yun Kim, Sung-sil Choo, Seok-won Hong, Yeseong Oh, Yerim Yang, Yoona Kim, Hee Jung Park and Sang-il Kim
Energies 2020, 13(2), 337; https://doi.org/10.3390/en13020337 - 10 Jan 2020
Cited by 7 | Viewed by 2736
Abstract
Significant bipolar conduction of the carriers in Bi2Te3-based alloys occurs at high temperatures due to their narrow bandgaps. Therefore, at high temperatures, their Seebeck coefficients decrease, the bipolar thermal conductivities rapidly increase, and the thermoelectric figure of merit, zT [...] Read more.
Significant bipolar conduction of the carriers in Bi2Te3-based alloys occurs at high temperatures due to their narrow bandgaps. Therefore, at high temperatures, their Seebeck coefficients decrease, the bipolar thermal conductivities rapidly increase, and the thermoelectric figure of merit, zT, rapidly decreases. In this study, band modification of n-type Cu0.008Bi2(Te,Se)3 alloys by sulfur (S) doping, which could widen the bandgap, is investigated regarding carrier transport properties and bipolar thermal conductivity. The increase in bandgap by S doping is demonstrated by the Goldsmid–Sharp estimation. The bipolar conduction reduction is shown in the carrier transport characteristics and thermal conductivity. In addition, S doping induces an additional point-defect scattering of phonons, which decreases the lattice thermal conductivity. Thus, the total thermal conductivity of the S-doped sample is reduced. Despite the reduced power factor due to the unfavorable change in the conduction band, zT at high temperatures is increased by S doping with simultaneous reductions in bipolar and lattice thermal conductivity. Full article
(This article belongs to the Special Issue 2D Energy Materials)
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