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Feature Papers in Energy Materials

A special issue of Materials (ISSN 1996-1944). This special issue belongs to the section "Energy Materials".

Deadline for manuscript submissions: closed (20 July 2023) | Viewed by 38117

Special Issue Editor

Dr. Aleksey Yaremchenko

E-Mail Website
Guest Editor
CICECO - Aveiro Institute of Materials, Department of Materials and Ceramic Engineering, University of Aveiro, 3810-193 Aveiro, Portugal
Interests: solid oxide fuel cells; solid oxide electrolysis cells; reversible solid electrolyte cells; high-temperature steam and carbon dioxide electrolysis; mixed-conducting ceramic membranes; MIEC membrane reactors; oxide-based ionic and mixed conductors

Special Issue Information

Dear colleagues

The special issue “Feature papers in Energy Materials” will collect high-quality original research papers and comprehensive reviews on the recent advances in the field of materials for harvesting, conversion, storage, transmission and utilization of energy. The issue intends to highlight new knowledge and latest innovative approaches and developments in all aspects of synthesis, processing, characterization and performance of functional energy materials and their integration in existing and emerging energy-related technologies. The potential topics include, but are not limited to:

  • Batteries and supercapacitors
  • Fuel cells
  • Water, steam and carbon dioxide electrolysis
  • Solar energy conversion
  • Photovoltaics
  • Thermoelectrics
  • Piezoelectrics
  • Phase change materials
  • Electrocatalysis and photocatalysis
  • Hydrogen technology
  • Biomass, biogas and biofuels

The Editorial Board members of the section Energy Materials of the journal Materials are encouraged to share their recent progress in their area of research, and to invite colleagues and relevant experts to contribute.

Dr. Aleksey Yaremchenko
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. Materials 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

  • batteries
  • biofuels
  • fuel cells
  • hydrogen
  • photovoltaics
  • piezoelectrics
  • solar energy
  • supercapacitors
  • thermoelectrics
  • thermoelectrics

Published Papers (16 papers)

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Research

Jump to: Review

15 pages, 3885 KiB  
Article
One-Step Microwave-Assisted Hydrothermal Preparation of Zn-ZnO(Nw)-rGO Electrodes for Supercapacitor Applications
by Cornelia Bandas, Mircea Nicolaescu, Mina Ionela Popescu, Corina Orha, Simona Căprărescu and Carmen Lazau
Materials 2023, 16(13), 4536; https://0-doi-org.brum.beds.ac.uk/10.3390/ma16134536 - 23 Jun 2023
Cited by 1 | Viewed by 1039
Abstract
Zn-ZnO(Nw)-rGO hybrid electrodes for supercapacitor applications were successfully prepared in situ by a one-step microwave-assisted hydrothermal method by deposition of reduced graphene oxide (rGO) on the structure of ZnO nanowires grown on the Zn foil. During the hydrothermal treatment, two processes occur the [...] Read more.
Zn-ZnO(Nw)-rGO hybrid electrodes for supercapacitor applications were successfully prepared in situ by a one-step microwave-assisted hydrothermal method by deposition of reduced graphene oxide (rGO) on the structure of ZnO nanowires grown on the Zn foil. During the hydrothermal treatment, two processes occur the reduction of graphene oxide (GO) and the deposition of rGO on the Zn-ZnO(Nw) support. The growth of ZnO nanowires was achieved by thermal oxidation below the melting point of the Zn foil in a controlled atmosphere. The as-obtained electrodes were assessed for structural, optical, and morphological properties by X-ray diffraction, Raman spectroscopy, ultraviolet-visible spectroscopy, SEM microscopy, and EDX analysis. The supercapacitor properties of the Zn-ZnO(Nw)-rGO hybrid electrodes were investigated by cyclic voltammetry, electrochemical impedance spectroscopy, and galvanostatic charge-discharge analysis. The CV curve reveals that the Zn-ZnO(Nw)-rGO hybrid structures work as negative electrodes and exhibit a non-ideal rectangle-like shape, suggesting that the as-synthesized structure behaves as a pseudo-capacitor. A maximum capacitance was determined to be 395.79 mF cm−2 at a scan rate of 5 mV s−1. Based on GCD analysis, the maximum specific capacitance of 145.59 mF cm−2 was achieved at a low power density of 2 mA cm−2. The cycle life assessment of the Zn-ZnO(Nw)-rGO hybrid electrode over a 250-cycle number was performed by CV and GCD analysis. The maximum retention rate of 120.86% was achieved from GCD analysis over 250 cycles for the Zn-ZnO(Nw)-rGO hybrid electrode. Full article
(This article belongs to the Special Issue Feature Papers in Energy Materials)
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17 pages, 20929 KiB  
Article
Pd–Co-Based Electrodes for Hydrogen Production by Water Splitting in Acidic Media
by Bernardo Patella, Claudio Zanca, Fabrizio Ganci, Sonia Carbone, Francesco Bonafede, Giuseppe Aiello, Rosario Miceli, Filippo Pellitteri, Philippe Mandin and Rosalinda Inguanta
Materials 2023, 16(2), 474; https://0-doi-org.brum.beds.ac.uk/10.3390/ma16020474 - 04 Jan 2023
Cited by 3 | Viewed by 1622
Abstract
To realize the benefits of a hydrogen economy, hydrogen must be produced cleanly, efficiently and affordably from renewable resources and, preferentially, close to the end-users. The goal is a sustainable cycle of hydrogen production and use: in the first stage of the cycle, [...] Read more.
To realize the benefits of a hydrogen economy, hydrogen must be produced cleanly, efficiently and affordably from renewable resources and, preferentially, close to the end-users. The goal is a sustainable cycle of hydrogen production and use: in the first stage of the cycle, hydrogen is produced from renewable resources and then used to feed a fuel cell. This cycle produces no pollution and no greenhouse gases. In this context, the development of electrolyzers producing high-purity hydrogen with a high efficiency and low cost is of great importance. Electrode materials play a fundamental role in influencing electrolyzer performances; consequently, in recent years considerable efforts have been made to obtain highly efficient and inexpensive catalyst materials. To reach both goals, we have developed electrodes based on Pd–Co alloys to be potentially used in the PEMEL electrolyzer. In fact, the Pd–Co alloy is a valid alternative to Pt for hydrogen evolution. The alloys were electrodeposited using two different types of support: carbon paper, to fabricate a porous structure, and anodic alumina membrane, to obtain regular arrays of nanowires. The goal was to obtain electrodes with very large active surface areas and a small amount of material. The research demonstrates that the electrochemical method is an ideal technique to obtain materials with good performances for the hydrogen evolution reaction. The Pd–Co alloy composition can be controlled by adjusting electrodeposition parameters (bath composition, current density and deposition time). The main results concerning the fabrication process and the characterization are presented and the performance in acid conditions is discussed. Full article
(This article belongs to the Special Issue Feature Papers in Energy Materials)
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12 pages, 4065 KiB  
Article
Effect of High-Voltage Additives on Formation of Solid Electrolyte Interphases in Lithium-Ion Batteries
by Minjing Chen, Yunbo Huang, Zhepu Shi, Hao Luo, Zhaoping Liu and Cai Shen
Materials 2022, 15(10), 3662; https://0-doi-org.brum.beds.ac.uk/10.3390/ma15103662 - 20 May 2022
Cited by 5 | Viewed by 2272
Abstract
Solid electrolyte interphase (SEI) formed at the interface in lithium-ion batteries plays an important role in isolating electrons and permeating ions during charging/discharging processes. Therefore, the formation of a good interface is crucial for better battery performance. In this study, additives based on [...] Read more.
Solid electrolyte interphase (SEI) formed at the interface in lithium-ion batteries plays an important role in isolating electrons and permeating ions during charging/discharging processes. Therefore, the formation of a good interface is crucial for better battery performance. In this study, additives based on adiponitrile (ADN) and trimethyl borate (TMB) were employed to broaden the electrochemical window and form a good SEI layer. Electrochemical Atomic force microscopy (EC-AFM) was used for in situ studies of film-formation mechanisms in high-voltage electrolytes on high-temperature pyrolytic graphite (HOPG), as well as Li- and Mn-rich (LMR) materials. X-ray photoelectron spectroscopy (XPS) combined with electrochemical methods revealed a synergistic reaction between the two additives to form a more stable interfacial film during charging/discharging processes to yield assembled batteries with improved cycle performance, its capacity increased from below 100 mAh/g to 200 mAh/g after 50 cycles. In sum, these findings would have great significance for the development of high voltage lithium-ion batteries with enhanced performance. Full article
(This article belongs to the Special Issue Feature Papers in Energy Materials)
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19 pages, 5170 KiB  
Article
Prospects of Using Pseudobrookite as an Iron-Bearing Mineral for the Alkaline Electrolytic Production of Iron
by Daniela V. Lopes, Aleksey D. Lisenkov, Luís C. M. Ruivo, Aleksey A. Yaremchenko, Jorge R. Frade and Andrei V. Kovalevsky
Materials 2022, 15(4), 1440; https://0-doi-org.brum.beds.ac.uk/10.3390/ma15041440 - 15 Feb 2022
Cited by 2 | Viewed by 2166
Abstract
The alkaline electrolytic production of iron is gaining interest due to the absence of CO2 emissions and significantly lower electrical energy consumption when compared with traditional steelmaking. The possibility of using an iron-bearing pseudobrookite mineral, Fe2TiO5, is explored [...] Read more.
The alkaline electrolytic production of iron is gaining interest due to the absence of CO2 emissions and significantly lower electrical energy consumption when compared with traditional steelmaking. The possibility of using an iron-bearing pseudobrookite mineral, Fe2TiO5, is explored for the first time as an alternative feedstock for the electrochemical reduction process. To assess relevant impacts of the presence of titanium, similar electroreduction processes were also performed for Fe2TiO5·Fe2O3 and Fe2O3. The electroreduction was attempted using dense and porous ceramic cathodes. Potentiostatic studies at the cathodic potentials of −1.15–−1.30 V vs. an Hg|HgO|NaOH reference electrode and a galvanostatic approach at 1 A/cm2 were used together with electroreduction from ceramic suspensions, obtained by grinding the porous ceramics. The complete electroreduction to Fe0 was only possible at high cathodic polarizations (−1.30 V), compromising the current efficiencies of the electrochemical process due to the hydrogen evolution reaction impact. Microstructural evolution and phase composition studies are discussed, providing trends on the role of titanium and corresponding electrochemical mechanisms. Although the obtained results suggest that pseudobrookite is not a feasible material to be used alone as feedstock for the electrolytic iron production, it can be considered with other iron oxide materials and/or ores to promote electroreduction. Full article
(This article belongs to the Special Issue Feature Papers in Energy Materials)
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22 pages, 9173 KiB  
Article
Development of Ni-Sr(V,Ti)O3-δ Fuel Electrodes for Solid Oxide Fuel Cells
by Bernardo F. Serôdio Costa, Blanca I. Arias-Serrano and Aleksey A. Yaremchenko
Materials 2022, 15(1), 278; https://0-doi-org.brum.beds.ac.uk/10.3390/ma15010278 - 30 Dec 2021
Cited by 4 | Viewed by 2152
Abstract
A series of strontium titanates-vanadates (STVN) with nominal cation composition Sr1-xTi1-y-zVyNizO3-δ (x = 0–0.04, y = 0.20–0.40 and z = 0.02–0.12) were prepared by a solid-state reaction route in [...] Read more.
A series of strontium titanates-vanadates (STVN) with nominal cation composition Sr1-xTi1-y-zVyNizO3-δ (x = 0–0.04, y = 0.20–0.40 and z = 0.02–0.12) were prepared by a solid-state reaction route in 10% H2–N2 atmosphere and characterized under reducing conditions as potential fuel electrode materials for solid oxide fuel cells. Detailed phase evolution studies using XRD and SEM/EDS demonstrated that firing at temperatures as high as 1200 °C is required to eliminate undesirable secondary phases. Under such conditions, nickel tends to segregate as a metallic phase and is unlikely to incorporate into the perovskite lattice. Ceramic samples sintered at 1500 °C exhibited temperature-activated electrical conductivity that showed a weak p(O2) dependence and increased with vanadium content, reaching a maximum of ~17 S/cm at 1000 °C. STVN ceramics showed moderate thermal expansion coefficients (12.5–14.3 ppm/K at 25–1100 °C) compatible with that of yttria-stabilized zirconia (8YSZ). Porous STVN electrodes on 8YSZ solid electrolytes were fabricated at 1100 °C and studied using electrochemical impedance spectroscopy at 700–900 °C in an atmosphere of diluted humidified H2 under zero DC conditions. As-prepared STVN electrodes demonstrated comparatively poor electrochemical performance, which was attributed to insufficient intrinsic electrocatalytic activity and agglomeration of metallic nickel during the high-temperature synthetic procedure. Incorporation of an oxygen-ion-conducting Ce0.9Gd0.1O2-δ phase (20–30 wt.%) and nano-sized Ni as electrocatalyst (≥1 wt.%) into the porous electrode structure via infiltration resulted in a substantial improvement in electrochemical activity and reduction of electrode polarization resistance by 6–8 times at 900 °C and ≥ one order of magnitude at 800 °C. Full article
(This article belongs to the Special Issue Feature Papers in Energy Materials)
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21 pages, 9648 KiB  
Article
Impact of A-Site Cation Deficiency on Charge Transport in La0.5−xSr0.5FeO3−δ
by Oleg V. Merkulov, Ruslan R. Samigullin, Alexey A. Markov and Mikhail V. Patrakeev
Materials 2021, 14(20), 5990; https://0-doi-org.brum.beds.ac.uk/10.3390/ma14205990 - 12 Oct 2021
Cited by 9 | Viewed by 1615
Abstract
The electrical conductivity of La0.5−xSr0.5FeO3−δ, investigated as a function of the nominal cation deficiency in the A-sublattice, x, varying from 0 to 0.02, has demonstrated a nonlinear dependence. An increase in the x value [...] Read more.
The electrical conductivity of La0.5−xSr0.5FeO3−δ, investigated as a function of the nominal cation deficiency in the A-sublattice, x, varying from 0 to 0.02, has demonstrated a nonlinear dependence. An increase in the x value from 0 to 0.01 resulted in a considerable increase in electrical conductivity, which was shown to be attributed mainly to an increase in the mobility of the charge carriers. A combined analysis of the defect equilibrium and the charge transport in La0.5−xSr0.5FeO3−δ revealed the increase in the mobility of oxygen ions, electrons, and holes by factors of ~1.5, 1.3, and 1.7, respectively. The observed effect is assumed to be conditioned by a variation in the oxide structure under the action of the cationic vacancy formation. It was found that the cation deficiency limit in La0.5−xSr0.5FeO3−δ did not exceed 0.01. A small overstep of this limit was shown to result in the formation of (Sr,La)Fe12O19 impurity, which even in undetectable amounts reduced the conductivity of the material. The presence of (Sr,La)Fe12O19 impurity was revealed by X-ray diffraction on the ceramic surface after heat treatment at 1300 °C. It is most likely that the formation of traces of the liquid phase under these conditions is responsible for the impurity migration to the ceramic surface. The introduction of a cation deficiency of 0.01 into the A-sublattice of La0.5−xSr0.5FeO3−δ can be recommended as an effective means to enhance both the oxygen ion and the electron conductivity and improve ceramic sinterability. Full article
(This article belongs to the Special Issue Feature Papers in Energy Materials)
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19 pages, 5638 KiB  
Article
CFD Numerical Modelling of a PV–TEG Hybrid System Cooled by Air Heat Sink Coupled with a Single-Phase Inverter
by Artur Wodołażski, Natalia Howaniec, Bartłomiej Jura, Andrzej Bąk and Adam Smoliński
Materials 2021, 14(19), 5800; https://0-doi-org.brum.beds.ac.uk/10.3390/ma14195800 - 04 Oct 2021
Cited by 4 | Viewed by 1895
Abstract
This study presents full transient, three-dimensional numerical models of a PV–TEG hybrid module coupled with single-phase inverter by co-simulation. The influence of factors, such as wind speed, solar radiation intensity, or ambient temperature on the PV–TEG system, was also examined. The numerical model [...] Read more.
This study presents full transient, three-dimensional numerical models of a PV–TEG hybrid module coupled with single-phase inverter by co-simulation. The influence of factors, such as wind speed, solar radiation intensity, or ambient temperature on the PV–TEG system, was also examined. The numerical model was implemented using Ansys software which accounted the phenomena of Thomson, Seebeck, and Joule’s heat place on the TEG system. Furthermore, its impact on total electrical efficiency was studied. The heat transfer surface of the passive heat sink and forced air circulation positively affected the total heat transfer, and therefore helped to maintain the electrical efficiency at a higher level. Simulation of the single-phase inverter with a PV–TEG system allows the determination of the power characteristics of the system in real time. The results of the study presented may provide a basis for performance optimization of a practical PV–TEG-inverter hybrid system co-design. Full article
(This article belongs to the Special Issue Feature Papers in Energy Materials)
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11 pages, 3557 KiB  
Article
Effect of Applied Pressure on the Electrical Resistance of Carbon Nanotube Fibers
by Chris J. Barnett, James D. McGettrick, Varun Shenoy Gangoli, Ewa Kazimierska, Alvin Orbaek White and Andrew R. Barron
Materials 2021, 14(9), 2106; https://0-doi-org.brum.beds.ac.uk/10.3390/ma14092106 - 21 Apr 2021
Cited by 4 | Viewed by 2665
Abstract
Carbon nanotubes (CNTs) can be spun into fibers as potential lightweight replacements for copper in electrical current transmission since lightweight CNT fibers weigh <1/6th that of an equivalently dimensioned copper wire. Experimentally, it has been shown that the electrical resistance of CNT fibers [...] Read more.
Carbon nanotubes (CNTs) can be spun into fibers as potential lightweight replacements for copper in electrical current transmission since lightweight CNT fibers weigh <1/6th that of an equivalently dimensioned copper wire. Experimentally, it has been shown that the electrical resistance of CNT fibers increases with longitudinal strain; however, although fibers may be under radial strain when they are compressed during crimping at contacts for use in electrical current transport, there has been no study of this relationship. Herein, we apply radial stress at the contact to a CNT fiber on both the nano- and macro-scale and measure the changes in fiber and contact resistance. We observed an increase in resistance with increasing pressure on the nanoscale as well as initially on the macro scale, which we attribute to the decreasing of axial CNT…CNT contacts. On the macro scale, the resistance then decreases with increased pressure, which we attribute to improved radial contact due to the closing of voids within the fiber bundle. X-ray photoelectron spectroscopy (XPS) and UV photoelectron spectroscopy (UPS) show that applied pressure on the fiber can damage the π–π bonding, which could also contribute to the increased resistance. As such, care must be taken when applying radial strain on CNT fibers in applications, including crimping for electrical contacts, lest they operate in an unfavorable regime with worse electrical performance. Full article
(This article belongs to the Special Issue Feature Papers in Energy Materials)
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9 pages, 1081 KiB  
Article
First-Principles Study of a MoS2-PbS van der Waals Heterostructure Inspired by Naturally Occurring Merelaniite
by Gemechis D. Degaga, Sumandeep Kaur, Ravindra Pandey and John A. Jaszczak
Materials 2021, 14(7), 1649; https://0-doi-org.brum.beds.ac.uk/10.3390/ma14071649 - 27 Mar 2021
Cited by 4 | Viewed by 2165
Abstract
Vertically stacked, layered van der Waals (vdW) heterostructures offer the possibility to design materials, within a range of chemistries and structures, to possess tailored properties. Inspired by the naturally occurring mineral merelaniite, this paper studies a vdW heterostructure composed of a MoS2 [...] Read more.
Vertically stacked, layered van der Waals (vdW) heterostructures offer the possibility to design materials, within a range of chemistries and structures, to possess tailored properties. Inspired by the naturally occurring mineral merelaniite, this paper studies a vdW heterostructure composed of a MoS2 monolayer and a PbS bilayer, using density functional theory. A commensurate 2D heterostructure film and the corresponding 3D periodic bulk structure are compared. The results find such a heterostructure to be stable and possess p-type semiconducting characteristics. Due to the heterostructure’s weak interlayer bonding, its carrier mobility is essentially governed by the constituent layers; the hole mobility is governed by the PbS bilayer, whereas the electron mobility is governed by the MoS2 monolayer. Furthermore, we estimate the hole mobility to be relatively high (~106 cm2V−1s−1), which can be useful for ultra-fast devices at the nanoscale. Full article
(This article belongs to the Special Issue Feature Papers in Energy Materials)
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20 pages, 6357 KiB  
Article
Prospects for Electrical Performance Tuning in Ca3Co4O9 Materials by Metallic Fe and Ni Particles Additions
by Gabriel Constantinescu, Sergey M. Mikhalev, Aleksey D. Lisenkov, Daniela V. Lopes, Artur R. Sarabando, Marta C. Ferro, Tiago F. da Silva, Sergii A. Sergiienko and Andrei V. Kovalevsky
Materials 2021, 14(4), 980; https://0-doi-org.brum.beds.ac.uk/10.3390/ma14040980 - 19 Feb 2021
Cited by 4 | Viewed by 2912
Abstract
This work further explores the possibilities for designing the high-temperature electrical performance of the thermoelectric Ca3Co4O9 phase, by a composite approach involving separate metallic iron and nickel particles additions, and by employing two different sintering schemes, capable to [...] Read more.
This work further explores the possibilities for designing the high-temperature electrical performance of the thermoelectric Ca3Co4O9 phase, by a composite approach involving separate metallic iron and nickel particles additions, and by employing two different sintering schemes, capable to promote the controlled interactions between the components, encouraged by our recent promising results obtained for similar cobalt additions. Iron and nickel were chosen because of their similarities with cobalt. The maximum power factor value of around 200 μWm−1K−2 at 925 K was achieved for the composite with the nominal nickel content of 3% vol., processed via the two-step sintering cycle, which provides the highest densification from this work. The effectiveness of the proposed approach was shown to be strongly dependent on the processing conditions and added amounts of metallic particles. Although the conventional one-step approach results in Fe- and Ni-containing composites with the major content of the thermoelectric Ca3Co4O9 phase, their electrical performance was found to be significantly lower than for the Co-containing analogue, due to the presence of less-conducting phases and excessive porosity. In contrast, the relatively high performance of the composite with a nominal nickel content of 3% vol. processed via a two-step approach is related to the specific microstructural features from this sample, including minimal porosity and the presence of the Ca2Co2O5 phase, which partially compensate the complete decomposition of the Ca3Co4O9 matrix. The obtained results demonstrate different pathways to tailor the phase composition of Ca3Co4O9-based materials, with a corresponding impact on the thermoelectric performance, and highlight the necessity of more controllable approaches for the phase composition tuning, including lower amounts and different morphologies of the dispersed metallic phases. Full article
(This article belongs to the Special Issue Feature Papers in Energy Materials)
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8 pages, 2193 KiB  
Article
Preparation and Electrical Properties of Silicone Composite Films Based on Silver Nanoparticle Decorated Multi-Walled Carbon Nanotubes
by Kwang Se Lee, Isheunesu Phiri, Sang Hern Kim, Kyeongkeun Oh and Jang Myoun Ko
Materials 2021, 14(4), 948; https://0-doi-org.brum.beds.ac.uk/10.3390/ma14040948 - 17 Feb 2021
Cited by 4 | Viewed by 2068
Abstract
The electrical properties of silicone composite films filled with silver (Ag) nanoparticle-decorated multi-walled carbon nanotubes (MWNT) prepared by solution processing are investigated. Pristine MWNT is oxidized and converted to the acyl chloride-functionalized MWNT using thionyl chloride, which is subsequently reacted with amine-terminated poly(dimethylsiloxane) [...] Read more.
The electrical properties of silicone composite films filled with silver (Ag) nanoparticle-decorated multi-walled carbon nanotubes (MWNT) prepared by solution processing are investigated. Pristine MWNT is oxidized and converted to the acyl chloride-functionalized MWNT using thionyl chloride, which is subsequently reacted with amine-terminated poly(dimethylsiloxane) (APDMS). Thereafter, APDMS-modified MWNT are decorated with Ag nanoparticles and then reacted with a poly(dimethylsiloxane) solution to form Ag-decorated MWNT silicone (Ag-decorated MWNT-APDMS/Silicone) composite. The morphological differences of the silicone composites containing Ag-decorated MWNT and APDMS-modified MWNT are observed by transmission electron microscopy (TEM) and the surface conductivities are measured by the four-probe method. Ag-decorated MWNT-APDMS/Silicone composite films show higher surface electrical conductivity than MWNT/silicone composite films. This shows that the electrical properties of Ag-decorated MWNT-APDMS/silicone composite films can be improved by the surface modification of MWNT with APDMS and Ag nanoparticles, thereby expanding their applications. Full article
(This article belongs to the Special Issue Feature Papers in Energy Materials)
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23 pages, 5760 KiB  
Article
The Effect of Refractory Wall Emissivity on the Energy Efficiency of a Gas-Fired Steam Cracking Pilot Unit
by Stijn Vangaever, Joost Van Thielen, Jeremy Hood, John Olver, Petra Honnerovà, Geraldine J. Heynderickx and Kevin M. Van Geem
Materials 2021, 14(4), 880; https://0-doi-org.brum.beds.ac.uk/10.3390/ma14040880 - 12 Feb 2021
Cited by 7 | Viewed by 2343
Abstract
The effect of high emissivity coatings on the radiative heat transfer in steam cracking furnaces is far from understood. To start, there is a lack of experimental data describing the emissive properties of the materials encountered in steam cracking furnaces. Therefore, spectral normal [...] Read more.
The effect of high emissivity coatings on the radiative heat transfer in steam cracking furnaces is far from understood. To start, there is a lack of experimental data describing the emissive properties of the materials encountered in steam cracking furnaces. Therefore, spectral normal emissivity measurements are carried out, evaluating the emissive properties of refractory firebricks before and after applying a high emissivity coating at elevated temperatures. The emissive properties are enhanced significantly after applying a high emissivity coating. Pilot unit steam cracking experiments show a 5% reduction in fuel gas firing rate after applying a high emissivity coating on the refractory of the cracking cells. A parametric study, showing the effect of reactor coil and furnace wall emissive properties on the radiative heat transfer inside a tube-in-box geometry, confirms that a non-gray gas model is required to accurately model the behavior of high emissivity coatings. Even though a gray gas model suffices to capture the heat sink behavior of a reactor coil, a non-gray gas model that is able to account for the absorption and re-emission in specific bands is necessary to accurately model the benefits of applying a high emissivity coating on the furnace wall. Full article
(This article belongs to the Special Issue Feature Papers in Energy Materials)
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23 pages, 6845 KiB  
Article
Mixed Ionic-Electronic Conductivity, Redox Behavior and Thermochemical Expansion of Mn-Substituted 5YSZ as an Interlayer Material for Reversible Solid Oxide Cells
by Alejandro Natoli, Blanca I. Arias-Serrano, Enrique Rodríguez-Castellón, Agnieszka Żurawska, Jorge R. Frade and Aleksey. A. Yaremchenko
Materials 2021, 14(3), 641; https://0-doi-org.brum.beds.ac.uk/10.3390/ma14030641 - 30 Jan 2021
Cited by 7 | Viewed by 2769
Abstract
Manganese-substituted 5 mol.% yttria-stabilized zirconia (5YSZ) was explored as a prospective material for protective interlayers between electrolyte and oxygen electrodes in reversible solid oxide fuel/electrolysis cells. [(ZrO2)0.95(Y2O3)0.05]1−x[MnOy]x [...] Read more.
Manganese-substituted 5 mol.% yttria-stabilized zirconia (5YSZ) was explored as a prospective material for protective interlayers between electrolyte and oxygen electrodes in reversible solid oxide fuel/electrolysis cells. [(ZrO2)0.95(Y2O3)0.05]1−x[MnOy]x (x = 0.05, 0.10 and 0.15) ceramics with cubic fluorite structure were sintered in air at 1600 °C. The characterization included X-ray diffraction (XRD), scanning electron microscopy (SEM)/energy dispersive spectroscopy (EDS), X-ray photoelectron spectroscopy (XPS), thermogravimetry and dilatometry in controlled atmospheres, electrical conductivity measurements, and determination of oxygen-ion transference numbers by the electromotive force (EMF) technique. Mn-substituted 5YSZ solid solutions exhibit variable oxygen nonstoichiometry with manganese cations in a mixed 2+/3+ oxidation state under oxidizing conditions. Substitution by manganese gradually increases the extent of oxygen content variation on thermal/redox cycling, chemical contribution to thermal expansion and dimensional changes on reduction. It also deteriorates oxygen-ionic conductivity and improves p-type electronic conductivity under oxidizing conditions, leading to a gradual transformation from predominantly ionic to prevailing electronic transport with increasing x. Mn2+/3+→Mn2+ transformation under reducing atmospheres is accompanied by the suppression of electronic transport and an increase in ionic conductivity. All Mn-substituted 5YSZ ceramics are solid electrolytes under reducing conditions. Prolonged treatments in reducing atmospheres, however, promote microstructural changes at the surface of bulk ceramics and Mn exsolution. Mn-substituted 5YSZ with 0.05 ≤ x < 0.10 is considered the most suitable for the interlayer application, due to the best combination of relevant factors, including oxygen content variations, levels of ionic/electronic conductivity and thermochemical expansion. Full article
(This article belongs to the Special Issue Feature Papers in Energy Materials)
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Review

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20 pages, 10299 KiB  
Review
2,7(3,6)-Diaryl(arylamino)-substituted Carbazoles as Components of OLEDs: A Review of the Last Decade
by Gintare Krucaite and Saulius Grigalevicius
Materials 2021, 14(22), 6754; https://0-doi-org.brum.beds.ac.uk/10.3390/ma14226754 - 09 Nov 2021
Cited by 10 | Viewed by 3075
Abstract
Organic light emitting diode (OLED) is a new, promising technology in the field of lighting and display applications due to the advantages offered by its organic electroactive derivatives over inorganic materials. OLEDs have prompted a great deal of investigations within academia as well [...] Read more.
Organic light emitting diode (OLED) is a new, promising technology in the field of lighting and display applications due to the advantages offered by its organic electroactive derivatives over inorganic materials. OLEDs have prompted a great deal of investigations within academia as well as in industry because of their potential applications. The electroactive layers of OLEDs can be fabricated from low molecular weight derivatives by vapor deposition or from polymers by spin coating from their solution. Among the low-molar-mass compounds under investigation in this field, carbazole-based materials have been studied at length for their useful chemical and electronic characteristics. The carbazole is an electron-rich heterocyclic compound, whose structure can be easily modified by rather simple reactions in order to obtain 2,7(3,6)-diaryl(arylamino)-substituted carbazoles. The substituted derivatives are widely used for the formation of OLEDs due to their good charge carrier injection and transfer characteristics, electroluminescence, thermally activated delayed fluorescence, improved thermal and morphological stability as well as their thin film forming characteristics. On the other hand, relatively high triplet energies of some substituted carbazole-based compounds make them useful components as host materials even for wide bandgap triplet emitters. The present review focuses on 2,7(3,6)-diaryl(arylamino)-substituted carbazoles, which were described in the last decade and were applied as charge-transporting layers, fluorescent and phosphorescent emitters as well as host materials for OLED devices. Full article
(This article belongs to the Special Issue Feature Papers in Energy Materials)
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16 pages, 4125 KiB  
Review
Coherence in the Ferroelectric A3ClO (A = Li, Na) Family of Electrolytes
by Maria Helena Braga
Materials 2021, 14(9), 2398; https://0-doi-org.brum.beds.ac.uk/10.3390/ma14092398 - 05 May 2021
Cited by 10 | Viewed by 2652
Abstract
Coherence is a major caveat in quantum computing. While phonons and electrons are weakly coupled in a glass, topological insulators strongly depend on the electron-phonon coupling. Knowledge of the electron−phonon interaction at conducting surfaces is relevant from a fundamental point of view as [...] Read more.
Coherence is a major caveat in quantum computing. While phonons and electrons are weakly coupled in a glass, topological insulators strongly depend on the electron-phonon coupling. Knowledge of the electron−phonon interaction at conducting surfaces is relevant from a fundamental point of view as well as for various applications, such as two-dimensional and quasi-1D superconductivity in nanotechnology. Similarly, the electron−phonon interaction plays a relevant role in other transport properties e.g., thermoelectricity, low-dimensional systems as layered Bi and Sb chalcogenides, and quasi-crystalline materials. Glass-electrolyte ferroelectric energy storage cells exhibit self-charge and self-cycling related to topological superconductivity and electron-phonon coupling; phonon coherence is therefore important. By recurring to ab initio molecular dynamics, it was demonstrated the tendency of the Li3ClO, Li2.92Ba0.04ClO, Na3ClO, and Na2.92Ba0.04ClO ferroelectric-electrolytes to keep phonon oscillation coherence for a short lapse of time in ps. Double-well energy potentials were obtained while the electrolyte systems were thermostatted in a heat bath at a constant temperature. The latter occurrences indicate ferroelectric type behavior but do not justify the coherent self-oscillations observed in all types of cells containing these families of electrolytes and, therefore, an emergent type phenomenon where the full cell works as a feedback system allowing oscillations coherence must be realized. A comparison with amorphous SiO2 was performed and the specific heats for the various species were calculated. Full article
(This article belongs to the Special Issue Feature Papers in Energy Materials)
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9 pages, 2627 KiB  
Review
Progress on V2O5 Cathodes for Multivalent Aqueous Batteries
by Emmanuel Karapidakis and Dimitra Vernardou
Materials 2021, 14(9), 2310; https://0-doi-org.brum.beds.ac.uk/10.3390/ma14092310 - 29 Apr 2021
Cited by 21 | Viewed by 2990
Abstract
Research efforts have been focused on developing multivalent ion batteries because they hold great promise and could be a major advancement in energy storage, since two or three times more charge per ion can be transferred as compared with lithium. However, their application [...] Read more.
Research efforts have been focused on developing multivalent ion batteries because they hold great promise and could be a major advancement in energy storage, since two or three times more charge per ion can be transferred as compared with lithium. However, their application is limited because of the lack of suitable cathode materials to reversibly intercalate multivalent ions. From that perspective, vanadium pentoxide is a promising cathode material because of its low toxicity, ease of synthesis, and layered structure, which provides huge possibilities for the development of energy storage devices. In this mini review, the general strategies required for the improvement of reversibility, capacity value, and stability of the cathodes is presented. The role of nanostructural morphologies, structure, and composites on the performance of vanadium pentoxide in the last five years is addressed. Finally, perspectives on future directions of the cathodes are proposed. Full article
(This article belongs to the Special Issue Feature Papers in Energy Materials)
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