Special Issue "Feature Paper in "Materials for Energy Applications" 2022–2023"

A special issue of Crystals (ISSN 2073-4352). This special issue belongs to the section "Materials for Energy Applications".

Deadline for manuscript submissions: closed (28 February 2023) | Viewed by 15286

Special Issue Editor

Department of Physics, University of Illinois at Chicago, Chicago, IL 60607, USA
Interests: transmission electron microscopy; scanning transmission electron microscopy; electron energy-loss spectroscopy; correlated oxides; molecular beam epitaxy; electron beam diffraction; magnetism
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

The journal Crystals (ISSN: 2073-4352) is pleased to announce the launch of a Special Issue titled “Feature Paper in “Materials for Energy Applications” 2022–2023”.

This Special Issue covers both experimental and theoretical works on functional energy materials.

Topics include but are not limited to:

  • Materials for thermoelectric energy conversion;
  • Inorganic and organic solar cell materials, including thin films and single-crystal devices;
  • Materials for rechargeable battery applications;
  • Supercapacitors;
  • Materials and approaches for hydrogen generation and storage;
  • Materials and approaches for water splitting;
  • Fuel cells;
  • Photocatalysis;
  • Piezoelectronics.

For this Special Issue, we aim to publish high-quality articles from our Editorial Board Members and other well-recognized scholars in this field. A discount on the article processing charge will be available for published papers.

Prof. Dr. Robert F. Klie
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. Crystals 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 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

  • material science
  • semiconductors
  • superconductors
  • energy materials
  • solar energy
  • water splitting
  • photovoltaics
  • ceramics
  • thin films
  • batteries
  • supercapacitors
  • X-ray diffraction
  • electron microscopy
  • device fabrication
  • thermoelectrics
  • energy storage
  • hydrogen evolution

Published Papers (12 papers)

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Research

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Article
Facile Synthesis of MXene/MnO2 Nanocomposites for Efficient Removal of Radionuclide Uranium
Crystals 2023, 13(5), 804; https://doi.org/10.3390/cryst13050804 - 11 May 2023
Viewed by 777
Abstract
The efficient removal of radionuclide uranium is crucial for sustainable nuclear energy and achieving a zero-carbon loop. In this study, we synthesized MXene/MnO2 nanocomposites and evaluated their ability to adsorb and reduce uranium. The results showed that the nanocomposites achieved a uranium [...] Read more.
The efficient removal of radionuclide uranium is crucial for sustainable nuclear energy and achieving a zero-carbon loop. In this study, we synthesized MXene/MnO2 nanocomposites and evaluated their ability to adsorb and reduce uranium. The results showed that the nanocomposites achieved a uranium removal rate of 99% and an adsorption capacity of 696 mg/g. Adsorption experiments were conducted under different conditions, including pH, cation, anion, and humic acid, and the uranium removal rate by the composite remained high at 91%, 70%, and 60% under the influence of pH = 4.97, 1.0 mM CaCl2, and 20 mg/L humic acid, respectively. The XRD and SEM analyses revealed that the uranium element was removed by the reduction and fixation of the composite material. These findings indicate that the MXene/MnO2 composite is an effective adsorption cleaning agent for the purification of radioactive nuclear wastewater, which has significant implications for pollution control. Full article
(This article belongs to the Special Issue Feature Paper in "Materials for Energy Applications" 2022–2023)
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Article
Inelastic Neutron Scattering Study of Phonon Dispersion Relation in Higher Manganese Silicides
Crystals 2023, 13(5), 741; https://doi.org/10.3390/cryst13050741 - 28 Apr 2023
Viewed by 1603
Abstract
We report inelastic neutron scattering (INS) measurements of the phonon dispersion relation in higher manganese silicides (HMSs). A large ingot of HMS is synthesized using a slow cooling method, which is found to have Mn15Si26 as the primary phase. The [...] Read more.
We report inelastic neutron scattering (INS) measurements of the phonon dispersion relation in higher manganese silicides (HMSs). A large ingot of HMS is synthesized using a slow cooling method, which is found to have Mn15Si26 as the primary phase. The sample is composed of highly oriented crystallites as confirmed by a neutron pole-figure study and thermal conductivity data. Our INS results are mostly consistent with earlier experimental and theoretical phonon studies in HMS, including the presence of a low-lying twisting mode. However, some discrepancies are also observed. Most notably, a 5 meV gap at the zone center and the softer dispersion relation of the low-lying twisting mode. We discuss the potential origins of these observations and their implications for the thermal properties of HMS. Full article
(This article belongs to the Special Issue Feature Paper in "Materials for Energy Applications" 2022–2023)
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Article
Deep-Blue Organic Light-Emitting Diodes Employed Traditional Hole Transporting Material as Emitter for 31-Inch 4K Flexible Display
Crystals 2023, 13(4), 687; https://doi.org/10.3390/cryst13040687 - 17 Apr 2023
Viewed by 736
Abstract
High-efficiency deep-blue organic light-emitting diodes (OLEDs) play a crucial role in realizing ultra-high-definition (UHD) flat-panel displays and reducing power consumption. Generally, most reported OLEDs with a Commission Internationale de L’Eclairage (CIE) y coordinate < 0.06 are achieved by traditional fluorescent deep-blue emitters. However, [...] Read more.
High-efficiency deep-blue organic light-emitting diodes (OLEDs) play a crucial role in realizing ultra-high-definition (UHD) flat-panel displays and reducing power consumption. Generally, most reported OLEDs with a Commission Internationale de L’Eclairage (CIE) y coordinate < 0.06 are achieved by traditional fluorescent deep-blue emitters. However, it is challenging to obtain deep-blue fluorescent OLEDs with a high external quantum efficiency (EQE) (reaching the theoretical limit of 5%). In this work, we have successfully employed a hole-transporting material for an emitter, which can increase the efficiency in deep-blue OLEDs. The device employed with the proposed hole-transporting material exhibits deep-blue emission peaks at 427.0 nm with CIE coordinates of (0.155, 0.051), a turn-on voltage (Von) of 4.5 V, and an EQE of 4.5%. The performance of the OLED can be improved by 5.0% by optimizing the device structure. Finally, the flexible display when using the OLED devices exhibited a high image quality. Full article
(This article belongs to the Special Issue Feature Paper in "Materials for Energy Applications" 2022–2023)
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Article
Effect of Substrate Temperature on Variations in the Structural and Optical Properties of Cu2O Thin Films Deposited via RF Magnetron Sputtering
Crystals 2023, 13(4), 643; https://doi.org/10.3390/cryst13040643 - 09 Apr 2023
Viewed by 1246
Abstract
In the present study, Cu2O films were deposited on a glass substrate via RF (radio frequency) magnetron sputtering under substrate temperature conditions that ranged from room temperature (RT, 25 °C) to 400 °C. The structural, compositional, and optical properties of the [...] Read more.
In the present study, Cu2O films were deposited on a glass substrate via RF (radio frequency) magnetron sputtering under substrate temperature conditions that ranged from room temperature (RT, 25 °C) to 400 °C. The structural, compositional, and optical properties of the Cu2O films were analyzed in relation to the experimental variables by applying various measurement methods. The substrate temperature was a crucial factor in shaping the structural, compositional, and optical properties of the Cu2O films that were synthesized via RF-magnetron sputtering. Our findings revealed that the Cu2O films exhibited a cubic structure, which was confirmed by XRD analysis. Specifically, the (111) and (200) planes showed different trends with respect to the substrate temperature. The intensity of the (111) peak increased at 250 °C, and above 300 °C, the preferred orientation of the (111) plane was maintained. The grain size, which was determined via FE-SEM, displayed a positive correlation with the substrate temperature. Additionally, XPS analysis revealed that the binding energy (BE) of the Cu2O film sputtered at 400 °C was similar to that which was previously reported. Notably, the as-grown Cu2O film demonstrated the highest transmittance (15.9%) in the visible region, which decreased with increasing substrate temperature. Furthermore, the energy band gap (Eg) of the Cu2O films remained constant (2.51 eV) at low substrate temperatures (25 °C to 200 °C) but exhibited a slight increase at higher temperatures, reaching 2.57 eV at 400 °C. Full article
(This article belongs to the Special Issue Feature Paper in "Materials for Energy Applications" 2022–2023)
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Article
Interlayer Investigations of GaN Heterostructures Integrated into Silicon Substrates by Surface Activated Bonding
Crystals 2023, 13(2), 217; https://doi.org/10.3390/cryst13020217 - 24 Jan 2023
Viewed by 1113
Abstract
Thinning the buffer layer thickness between the GaN epilayer and Si substrate without introducing large residual stress is persistently desired for GaN-on-Si devices to promote their thermal budgets and low-cost, multifunctional applications. In this work, the GaN-on-Si heterostructures were directly bonded at room [...] Read more.
Thinning the buffer layer thickness between the GaN epilayer and Si substrate without introducing large residual stress is persistently desired for GaN-on-Si devices to promote their thermal budgets and low-cost, multifunctional applications. In this work, the GaN-on-Si heterostructures were directly bonded at room temperature by surface activated bonding (SAB) and the therein residual stress states were investigated by confocal micro-Raman. The effects of thermal annealing process on the residual stress and interfacial microstructure in SAB fabricated GaN-on-Si heterostructures were also systematically investigated by in situ micro-Raman and transmission electron microscopy. It was found that a significant relaxation and a more uniform stress distribution was obtained in SAB bonded GaN-on-Si heterostructure in comparison with that of MOCVD grown sample; however, with increasing annealing temperature, the residual stresses at the SAB bonded GaN layer and Si layer evolute monotonically in different trends. The main reason can be ascribed to the amorphous layer formed at the bonding interface, which played a critical stress relaxation role and transformed into a much thinner crystallized interlayer without any observable structural defects after 1000 °C annealing. Full article
(This article belongs to the Special Issue Feature Paper in "Materials for Energy Applications" 2022–2023)
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Article
Adsorption of Orange G Dye on Hydrophobic Activated Bentonite from Aqueous Solution
Crystals 2023, 13(2), 211; https://doi.org/10.3390/cryst13020211 - 24 Jan 2023
Cited by 1 | Viewed by 943
Abstract
This report focusses on the modification of physical structure and chemical properties of a bentonite clay from the Hammam Boughrara region of the Maghnia district in western Algeria to maximize its adsorption capacity. The purified bentonite clay (called B) was modified, either by [...] Read more.
This report focusses on the modification of physical structure and chemical properties of a bentonite clay from the Hammam Boughrara region of the Maghnia district in western Algeria to maximize its adsorption capacity. The purified bentonite clay (called B) was modified, either by acid activation with 1M sulfuric acid (B-Act), or by intercalation with the cationic surfactant cetytrimethyl ammonium bromide (CTAB), applying a cation exchange capacity (CEC) of 100% (called B-CTAB). Modification of B was also introduced by combining these two steps consecutively, i.e., at first acid activation of B, followed by intercalation with CTAB (B-Act-CTAB). The B-Act-CTAB was obtained by H2SO4 (1M) acid activation, followed by co-adsorption of CTAB with 100% and 300% of the CEC of B-Act as precursor. In particular, a strong increase of surface area and pore volume of the modified bentonites was observed for B-Act (469.83 m²/g and 0.401 cm3g−1), B-Act-CTAB100 (267.72 m²/g and 0.316 cm3 g−1) and B-Act-CTAB300 (111.15 m²/g and 0.171 cm3g−1), compared to B (31.79 m²/g and 0.074 cm3 g−1) and B-CTAB (3.79 m²/g and 0.034 cm3 g−1), respectively. The bentonite-based adsorbents were then used to evaluate the removal efficiency of an organic molecule, the azo dye Orange G (OG), as a model for a Persistent Organic Pollutant. Freundlich, Langmuir and Sips (Langmuir–Freundlich) models were applied to analyze equilibrium isotherms, showing a good correlation between experimental data and the Freundlich model. A good agreement was obtained between experimentally obtained kinetic adsorption data and the pseudo-second-order model, allowing to evaluate rate constants. B-Act-CTAB300 can be applied as a low-cost material for removal of azo dyes, since its adsorption capacity towards OG (102.80 mg/g) exceeds largely that of B-CTAB (31.49 mg/g) and B-Act-CTAB100 (12.77 mg/g). Full article
(This article belongs to the Special Issue Feature Paper in "Materials for Energy Applications" 2022–2023)
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Article
Photocatalytic Dye Decomposition over CaMnO3−δ and Pr0.5Ca0.5MnO3: A Combined XPS and DFT Study
Crystals 2022, 12(12), 1728; https://doi.org/10.3390/cryst12121728 - 28 Nov 2022
Viewed by 1003
Abstract
In the field of environmental sustainability, the development of highly efficient photocatalytic under a wide wavelength range with band engineering is regarded as a promising strategy to enhance photocatalytic dye degradation. Here, we report on CaMnO3−δ and Pr0.5Ca0.5MnO [...] Read more.
In the field of environmental sustainability, the development of highly efficient photocatalytic under a wide wavelength range with band engineering is regarded as a promising strategy to enhance photocatalytic dye degradation. Here, we report on CaMnO3−δ and Pr0.5Ca0.5MnO3 perovskite materials prepared by a sol-gel combustion method. From X-ray photoelectron spectroscopy (XPS), the particle surfaces of both compounds are oxygen deficient, while the surface hydroxyl and carbonyl groups’ adsorption on the surface of Pr0.5Ca0.5MnO3 particles is more pronounced. FT-FIR spectroscopy has been used to investigate the covalent bonds and oxygen vacancy characteristics. Photocatalytic activities were investigated by the degradation of methylene blue and methyl orange under UV light. It was observed that both dye molecules are more degraded over CaMnO3−δ. The underlying mechanisms behind the photoexcitation and degradation process are established via the Spin-polarized Density Functional Theory (DFT). Full article
(This article belongs to the Special Issue Feature Paper in "Materials for Energy Applications" 2022–2023)
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Article
Multiscale Simulations for Defect-Controlled Processing of Group IV Materials
Crystals 2022, 12(12), 1701; https://doi.org/10.3390/cryst12121701 - 24 Nov 2022
Cited by 2 | Viewed by 1539
Abstract
Multiscale approaches for the simulation of materials processing are becoming essential to the industrialization of future nanotechnologies, as they allow for a reduction in production costs and an enhancement of devices and applications. Their integration as modules of “digital twins”, i.e., a combined [...] Read more.
Multiscale approaches for the simulation of materials processing are becoming essential to the industrialization of future nanotechnologies, as they allow for a reduction in production costs and an enhancement of devices and applications. Their integration as modules of “digital twins”, i.e., a combined sequence of predictive chemical–physical simulations and trained black-box techniques, should ideally complement the real sequence of processes throughout all development and production stages, starting from the growth of materials, their functional manipulation and finally their integration in nano-devices. To achieve this framework, computational implementations at different space and time scales are necessary, ranging from the atomistic to the macro-scale. In this paper, we propose a general paradigm for the industrially driven computational modeling of materials by deploying a multiscale methodology based on physical–chemical simulations bridging macro, meso and atomic scale. We demonstrate its general applicability by studying two completely different processing examples, i.e., the growth of group IV crystals through physical vapor deposition and their thermal treatment through pulsed laser annealing. We indicate the suitable formalisms, as well as the advantages and critical issues associated with each scale, and show how numerical methods for the solution of the models could be coupled to achieve a complete and effective virtualization of the process. By connecting the process parameters to atomic scale modifications such as lattice defects or faceting, we highlight how a digital twin module can gain intrinsic predictivity far from the pre-assessed training conditions of black-box “Virtual Metrology” techniques. Full article
(This article belongs to the Special Issue Feature Paper in "Materials for Energy Applications" 2022–2023)
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Article
Predicting the Crystal Structure and Lattice Parameters of the Perovskite Materials via Different Machine Learning Models Based on Basic Atom Properties
Crystals 2022, 12(11), 1570; https://doi.org/10.3390/cryst12111570 - 03 Nov 2022
Cited by 6 | Viewed by 1891
Abstract
Perovskite materials have high potential for the renewable energy sources such as solar PV cells, fuel cells, etc. Different structural distortions such as crystal structure and lattice parameters have a critical impact on the determination of the perovskite’s structure strength, stability, and overall [...] Read more.
Perovskite materials have high potential for the renewable energy sources such as solar PV cells, fuel cells, etc. Different structural distortions such as crystal structure and lattice parameters have a critical impact on the determination of the perovskite’s structure strength, stability, and overall performance of the materials in the applications. To improve the perovskite performance and accelerate the prediction of different structural distortions, few ML models have been established to predict the type of crystal structures and their lattice parameters using the basic atom characteristics of the perovskite materials. In this work, different ML models such as random forest (RF), support vector machine (SVM), neural network (NN), and genetic algorithm (GA) supported neural network (GA-NN) have been established, whereas support vector regression (SVR) and genetic algorithm-supported support vector regression (GA-SVR) models have been assessed for the prediction of the lattice parameters. The prediction model accuracy for the crystal structure classification is almost 88% in average for GA-NN whereas for the lattice constants regression model GA-SVR model gives ~95% in average which can be further improved by accumulating more robust datasets into the database. These ML models can be used as an alternative process to accelerate the development of finding out new perovskite material by providing valuable insight for the behaviours of the perovskite materials. Full article
(This article belongs to the Special Issue Feature Paper in "Materials for Energy Applications" 2022–2023)
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Article
Study of the Thermal Properties and Lattice Disorder Effects in CdTe–Based Crystals: CdBeTe, CdMnTe, and CdZnTe
Crystals 2022, 12(11), 1555; https://doi.org/10.3390/cryst12111555 - 31 Oct 2022
Cited by 3 | Viewed by 1169
Abstract
Mixed semiconductor ternary crystals were grown using the Bridgman–Stockbarger method. This is a high–temperature and high–pressure crystal growth method. Cd1–xBexTe crystals were grown in the range of composition 0 < x < 0.1, such as 0.00, 0.01, 0.03, 0.05, [...] Read more.
Mixed semiconductor ternary crystals were grown using the Bridgman–Stockbarger method. This is a high–temperature and high–pressure crystal growth method. Cd1–xBexTe crystals were grown in the range of composition 0 < x < 0.1, such as 0.00, 0.01, 0.03, 0.05, and 0.1. The main goal of this paper was to compare the thermal properties of CdBeTe with previously grown CdMnTe and CdZnTe–mixed ternary crystals. The photopyroelectric technique was applied to examine the thermal properties. The thermal diffusivity and effusivity values were obtained after testing all the samples, and the thermal conductivity was calculated then. As such, a complete thermal characterization of the crystals was carried out. For further characterization, the thermal conductivity versus composition was checked by applying the Sadao Adachi model. Thanks to that, we were able to determine the total thermal resistivity of the crystals and the additional resistivity which arises from the lattice disorder. As such, the disorder effects arising from substituting the native atom with a foreign one were characterized for all crystals. We were looking for the best substitution of the Cd atom in the CdTe matrix based on the compounds’ thermal properties. It turned out that Zn and Mn introduce a similar disorder, with Be being the highest one. Full article
(This article belongs to the Special Issue Feature Paper in "Materials for Energy Applications" 2022–2023)
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Article
Laser Terahertz Emission Microscope for Imaging Grain Heterogeneity: A Case Study of CH3NH3PbI3 Perovskite Semiconductors
Crystals 2022, 12(10), 1462; https://doi.org/10.3390/cryst12101462 - 17 Oct 2022
Viewed by 1070
Abstract
Strong terahertz (THz) emission from the methylammonium lead iodide (MAPbI3) perovskite semiconductors has been observed following above-bandgap photoexcitation, yet local THz responses of crystalline microstructures are absent. We implement laser THz emission microscope (LTEM), yet-to-be applied to the perovskite semiconductors, as [...] Read more.
Strong terahertz (THz) emission from the methylammonium lead iodide (MAPbI3) perovskite semiconductors has been observed following above-bandgap photoexcitation, yet local THz responses of crystalline microstructures are absent. We implement laser THz emission microscope (LTEM), yet-to-be applied to the perovskite semiconductors, as a novel and complementary tool to evaluate the electronic and grain heterogeneity of MAPbI3 thin films. Two MAPbI3 samples with different grain sizes are studied. Using this approach, we show that the one with a larger grain size gives more uniform THz radiation. More significant spatial THz intensity fluctuation is observed for the sample with a smaller grain size. Full article
(This article belongs to the Special Issue Feature Paper in "Materials for Energy Applications" 2022–2023)
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Review

Jump to: Research

Review
Li-Rich Layered Oxides: Structure and Doping Strategies to Enable Co-Poor/Co-Free Cathodes for Li-Ion Batteries
Crystals 2023, 13(2), 204; https://doi.org/10.3390/cryst13020204 - 23 Jan 2023
Cited by 2 | Viewed by 1703
Abstract
Lithium-rich layered oxides (LRLO) are a wide class of innovative active materials used in positive electrodes in lithium-ion (LIB) and lithium–metal secondary batteries (LMB). LRLOs are over-stoichiometric layered oxides rich in lithium and manganese with a general formula Li1+xTM1−xO [...] Read more.
Lithium-rich layered oxides (LRLO) are a wide class of innovative active materials used in positive electrodes in lithium-ion (LIB) and lithium–metal secondary batteries (LMB). LRLOs are over-stoichiometric layered oxides rich in lithium and manganese with a general formula Li1+xTM1−xO2, where TM is a blend of transition metals comprising Mn (main constituent), Ni, Co, Fe and others. Due to their very variable composition and extended defectivity, their structural identity is still debated among researchers, being likely an unresolved hybrid between a monoclinic (mC24) and a hexagonal lattice (hR12). Once casted in composite positive electrode films and assembled in LIBs or LMBs, LRLOs can deliver reversible specific capacities above 220–240 mAhg−1, and thus they exceed any other available intercalation cathode material for LIBs, with mean working potential above 3.3–3.4 V vs Li for hundreds of cycles in liquid aprotic commercial electrodes. In this review, we critically outline the recent advancements in the fundamental understanding of the physical–chemical properties of LRLO as well as the most exciting innovations in their battery performance. We focus in particular on the elusive structural identity of these phases, on the complexity of the reaction mechanism in batteries, as well as on practical strategies to minimize or remove cobalt from the lattice while preserving its outstanding performance upon cycling. Full article
(This article belongs to the Special Issue Feature Paper in "Materials for Energy Applications" 2022–2023)
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