International Journal of Molecular Sciences

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Open AccessEditorial

Editorial of Special Issue “Materials for Energy Applications 2.0”

by Sun-Jae Kim

Int. J. Mol. Sci. 2023, 24(5), 4892; https://doi.org/10.3390/ijms24054892 - 3 Mar 2023

Cited by 1 | Viewed by 1106

Abstract

Energy is a key factor in determining the growth of human society [...] Full article

(This article belongs to the Special Issue Materials for Energy Applications 2.0)

Research

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17 pages, 5648 KiB

Open AccessArticle

A First-Principles Investigation on the Structural, Optoelectronic, and Thermoelectric Properties of Pyrochlore Oxides (La₂Tm₂O₇ (Tm = Hf, Zr)) for Energy Applications

by Zeesham Abbas, Sajjad Hussain, Shabbir Muhammad, Saifeldin M. Siddeeg and Jongwan Jung

Int. J. Mol. Sci. 2022, 23(23), 15266; https://doi.org/10.3390/ijms232315266 - 3 Dec 2022

Cited by 16 | Viewed by 1788

Abstract

A first-principles calculation based on DFT investigations on the structural, optoelectronic, and thermoelectric characteristics of the newly designed pyrochlore oxides La₂Tm₂O₇ (Tm = Hf, Zr) is presented in this study. The main quest of the researchers working in [...] Read more.

A first-principles calculation based on DFT investigations on the structural, optoelectronic, and thermoelectric characteristics of the newly designed pyrochlore oxides La₂Tm₂O₇ (Tm = Hf, Zr) is presented in this study. The main quest of the researchers working in the field of renewable energy is to manufacture suitable materials for commercial applications such as thermoelectric and optoelectronic devices. From the calculated structural properties, it is evident that La₂Hf₂O₇ is more stable compared to La₂Zr₂O₇. La₂Hf₂O₇ and La₂Zr₂O₇ are direct bandgap materials having energy bandgaps of 4.45 and 4.40 eV, respectively. No evidence regarding magnetic moment is obtained from the spectra of TDOS, as a similar overall profile for both spin channels can be noted. In the spectra of

ε_{2} (ω)

, it is evident that these materials absorb maximum photons in the UV region and are potential candidates for photovoltaic device applications. La₂Tm₂O₇ (Tm = Hf, Zr) are also promising candidates for thermoelectric device applications, as these p-type materials possess

Z T

values of approximately 1, which is the primary criterion for efficient thermoelectric materials. Full article

(This article belongs to the Special Issue Materials for Energy Applications 2.0)

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13 pages, 3041 KiB

Open AccessArticle

Carbon-Coated ZnS-FeS₂ Heterostructure as an Anode Material for Lithium-Ion Battery Applications

by Perumal Naveenkumar, Munisamy Maniyazagan, Nayoung Kang, Hyeon-Woo Yang, Woo-Seung Kang and Sun-Jae Kim

Int. J. Mol. Sci. 2022, 23(22), 13945; https://doi.org/10.3390/ijms232213945 - 11 Nov 2022

Cited by 7 | Viewed by 2088

Abstract

The construction of carbon-coated heterostructures of bimetallic sulfide is an effective technique to improve the electrochemical activity of anode materials in lithium-ion batteries. In this work, the carbon-coated heterostructured ZnS-FeS₂ is prepared by a two-step hydrothermal method. The crystallinity and nature of [...] Read more.

The construction of carbon-coated heterostructures of bimetallic sulfide is an effective technique to improve the electrochemical activity of anode materials in lithium-ion batteries. In this work, the carbon-coated heterostructured ZnS-FeS₂ is prepared by a two-step hydrothermal method. The crystallinity and nature of carbon-coating are confirmed by the investigation of XRD and Raman spectroscopy techniques. The nanoparticle morphology of ZnS and plate-like morphology of FeS₂ is established by TEM images. The chemical composition of heterostructure ZnS-FeS₂@C is discovered by an XPS study. The CV results have disclosed the charge storage mechanism, which depends on the capacitive and diffusion process. The BET surface area (37.95 m²g⁻¹) and lower R_ct value (137 Ω) of ZnS-FeS₂@C are beneficial to attain higher lithium-ion storage performance. It delivered a discharge capacity of 821 mAh g⁻¹ in the 500th continuous cycle @ A g⁻¹, with a coulombic efficiency of around 100%, which is higher than the ZnS-FeS₂ heterostructure (512 mAh g⁻¹). The proposed strategy can improve the electrochemical performance and stability of lithium-ion batteries, and can be helpful in finding highly effective anode materials for energy storage devices. Full article

(This article belongs to the Special Issue Materials for Energy Applications 2.0)

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19 pages, 14054 KiB

Open AccessArticle

Concentration Optimization of Localized Cu⁰ and Cu⁺ on Cu-Based Electrodes for Improving Electrochemical Generation of Ethanol from Carbon Dioxide

by Hong Lu, Guan Wang, Yong Zhou, Aselefech Sorsa Wotango, Jiahao Wu, Qi Meng and Ping Li

Int. J. Mol. Sci. 2022, 23(16), 9373; https://doi.org/10.3390/ijms23169373 - 19 Aug 2022

Cited by 6 | Viewed by 2319

Abstract

Copper-based electrodes can catalyze electroreduction of CO₂ to two-carbon products. However, obtaining a specific product with high efficiency depends on the oxidation state of Cu for the Cu-based materials. In this study, Cu-based electrodes were prepared on fluorinated tin oxide (FTO) using [...] Read more.

Copper-based electrodes can catalyze electroreduction of CO₂ to two-carbon products. However, obtaining a specific product with high efficiency depends on the oxidation state of Cu for the Cu-based materials. In this study, Cu-based electrodes were prepared on fluorinated tin oxide (FTO) using the one-step electrodeposition method. These electrodes were used as efficient electrocatalysts for CO₂ reduction to ethanol. The concentration ratio of Cu⁰ and Cu⁺ on the electrodes was precisely modulated by adding monoethanolamine (MEA). The results of spectroscopic characterization showed that the concentration ratio of localized Cu⁺ and Cu⁰ (Cu⁺/Cu⁰) on the Cu-based electrodes was controlled from 1.24/1 to 1.54/1 by regulating the amount of MEA. It was found that the electrode exhibited the best electrochemical efficiency and ethanol production in the CO₂ reduction reaction at the optimal concentration ratio Cu⁺/Cu⁰ of 1.42/1. The maximum faradaic efficiencies of ethanol and C₂ were 48% and 77%, respectively, at the potential of −0.6 V vs. a reversible hydrogen electrode (RHE). Furthermore, the optimal concentration ratio of Cu⁺/Cu⁰ achieved the balance between Cu⁺ and Cu⁰ with the most favorable free energy for the formation of *CO intermediate. The stable existence of the *CO intermediate significantly contributed to the formation of the C–C bond for ethanol production. Full article

(This article belongs to the Special Issue Materials for Energy Applications 2.0)

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18 pages, 4241 KiB

Open AccessArticle

Hematites Precipitated in Alkaline Precursors: Comparison of Structural and Textural Properties for Methane Oxidation

by Marta Valášková, Pavel Leštinský, Lenka Matějová, Kateřina Klemencová, Michal Ritz, Christian Schimpf, Mykhailo Motylenko, David Rafaja and Jakub Bělík

Int. J. Mol. Sci. 2022, 23(15), 8163; https://doi.org/10.3390/ijms23158163 - 25 Jul 2022

Cited by 2 | Viewed by 2026

Abstract

Hematite (α-Fe₂O₃) catalysts prepared using the precipitation methods was found to be highly effective, and therefore, it was studied with methane (CH₄), showing an excellent stable performance below 500 °C. This study investigates hematite nanoparticles (NPs) obtained [...] Read more.

Hematite (α-Fe₂O₃) catalysts prepared using the precipitation methods was found to be highly effective, and therefore, it was studied with methane (CH₄), showing an excellent stable performance below 500 °C. This study investigates hematite nanoparticles (NPs) obtained by precipitation in water from the precursor of ferric chloride hexahydrate using precipitating agents NaOH or NH₄OH at maintained pH 11 and calcined up to 500 °C for the catalytic oxidation of low concentrations of CH₄ (5% by volume in air) at 500 °C to compare their structural state in a CH₄ reducing environment. The conversion (%) of CH₄ values decreasing with time was discussed according to the course of different transformation of goethite and hydrohematites NPs precursors to magnetite and the structural state of the calcined hydrohematites. The phase composition, the size and morphology of nanocrystallites, thermal transformation of precipitates and the specific surface area of the NPs were characterized in detail by X-ray powder diffraction, transmission electron microscopy, infrared spectroscopy, thermal TG/DTA analysis and nitrogen physisorption measurements. The results support the finding that after goethite dehydration, transformation to hydrohematite due to structurally incorporated water and vacancies is different from hydrohematite α-Fe₂O₃. The surface area SBET of Fe₂O₃_NH-70 precipitate composed of protohematite was larger by about 53 m²/g in comparison with Fe₂O₃_Na-70 precipitate composed of goethite. The oxidation of methane was positively influenced by the hydrohematites of the smaller particle size and the largest lattice volume containing structurally incorporated water and vacancies. Full article

(This article belongs to the Special Issue Materials for Energy Applications 2.0)

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14 pages, 4648 KiB

Open AccessArticle

Laser Shock Fabrication of Nitrogen Doped Inverse Spinel Fe₃O₄/Carbon Nanosheet Film Electrodes towards Hydrogen Evolution Reactions in Alkaline Media

by Dun Wu, Jiaming Zhao, Junfeng Cheng, Chunlin Liu and Qiang Wang

Int. J. Mol. Sci. 2022, 23(13), 7477; https://doi.org/10.3390/ijms23137477 - 5 Jul 2022

Cited by 5 | Viewed by 2032

Abstract

The reliable and cost-effective production of high-performance film electrodes for hydrogen evolution reactions remains a challenge for the laser surface modification community. In this study, prior to a thermal imidization reaction, a small number of Fe₃O₄ nanoparticles were vortexed into [...] Read more.

The reliable and cost-effective production of high-performance film electrodes for hydrogen evolution reactions remains a challenge for the laser surface modification community. In this study, prior to a thermal imidization reaction, a small number of Fe₃O₄ nanoparticles were vortexed into a poly(amic acid) (PAA) prepolymer, and the achieved flat composite film was then ablated by a 1064 nm fiber laser. After laser irradiation, the hierarchical architectures of carbon nanosheets decorated with Fe₃O₄ nanoparticles were generated. Although pure polyimide (PI) film and laser carbonized PI film, as well as bare Fe₃O₄, showcase poor intrinsic catalytic activity toward alkaline hydrogen evolution reactions, our laser-derived Fe₃O₄/carbon nanosheet hybrid film demonstrated enhanced electrocatalytic activity and stability in 1 M KOH electrolyte; the overpotential(η₁₀) reached 247 mV when the current density was 10 mA cm⁻² with a slight current decay in the chronoamperometric examination of 12 h. Finally, we proposed that the substitution of N to O in Fe−O sites of trans spinel structured magnetite would be able to modulate the free energy of hydrogen adsorption (ΔG_H*) and accelerate water dissociation. Full article

(This article belongs to the Special Issue Materials for Energy Applications 2.0)

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13 pages, 4350 KiB

Open AccessArticle

A Flower-like In₂O₃ Catalyst Derived via Metal–Organic Frameworks for Photocatalytic Applications

by Maniyazagan Munisamy, Hyeon-Woo Yang, Naveenkumar Perumal, Nayoung Kang, Woo Seung Kang and Sun-Jae Kim

Int. J. Mol. Sci. 2022, 23(8), 4398; https://doi.org/10.3390/ijms23084398 - 15 Apr 2022

Cited by 12 | Viewed by 2729

Abstract

The most pressing concerns in environmental remediation are the design and development of catalysts with benign, low-cost, and efficient photocatalytic activity. The present study effectively generated a flower-like indium oxide (In₂O₃-MF) catalyst employing a convenient MOF-based solvothermal self-assembly technique. [...] Read more.

The most pressing concerns in environmental remediation are the design and development of catalysts with benign, low-cost, and efficient photocatalytic activity. The present study effectively generated a flower-like indium oxide (In₂O₃-MF) catalyst employing a convenient MOF-based solvothermal self-assembly technique. The In₂O₃-MF photocatalyst exhibits a flower-like structure, according to morphology and structural analysis. The enhanced photocatalytic activity of the In₂O₃-MF catalyst for 4-nitrophenol (4-NP) and methylene blue (MB) is likely due to its unique 3D structure, which includes a large surface area (486.95 m² g⁻¹), a wide spectrum response, and the prevention of electron–hole recombination compared to In₂O₃-MR (indium oxide-micro rod) and In₂O₃-MD (indium oxide-micro disc). In the presence of NaBH₄ and visible light, the catalytic performances of the In₂O₃-MF, In₂O₃-MR, and In₂O₃-MD catalysts for the reduction of 4-NP and MB degradation were investigated. Using In₂O₃-MF as a catalyst, we were able to achieve a 99.32 percent reduction of 4-NP in 20 min and 99.2 percent degradation of MB in 3 min. Interestingly, the conversion rates of catalytic 4-NP and MB were still larger than 95 and 96 percent after five consecutive cycles of catalytic tests, suggesting that the In₂O₃-MF catalyst has outstanding catalytic performance and a high reutilization rate. Full article

(This article belongs to the Special Issue Materials for Energy Applications 2.0)

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14 pages, 2486 KiB

Open AccessArticle

Comparison of Pore Structures of Cellulose-Based Activated Carbon Fibers and Their Applications for Electrode Materials

by Ju-Hwan Kim, Sang-Chul Jung, Hye-Min Lee and Byung-Joo Kim

Int. J. Mol. Sci. 2022, 23(7), 3680; https://doi.org/10.3390/ijms23073680 - 27 Mar 2022

Cited by 24 | Viewed by 3690

Abstract

This study presents the first investigation of cellulose-based activated carbon fibers (RACFs) prepared as electrode materials for the electric double-layer capacitor (EDLC) in lieu of activated carbon, to determine its efficacy as a low-cost, environmentally friendly enhancement alternative to nanocarbon materials. The RACFs [...] Read more.

This study presents the first investigation of cellulose-based activated carbon fibers (RACFs) prepared as electrode materials for the electric double-layer capacitor (EDLC) in lieu of activated carbon, to determine its efficacy as a low-cost, environmentally friendly enhancement alternative to nanocarbon materials. The RACFs were prepared by steam activation and their textural properties were studied by Brunauer–Emmett–Teller and non-localized density functional theory equations with N₂/77K adsorption isotherms. The crystallite structure of the RACFs was observed by X-ray diffraction. The RACFs were applied as an electrode material for an EDLC and compared with commercial activated carbon (YP-50F). The electrochemical performance of the EDLC was analyzed using galvanostatic charge/discharge curves, cyclic voltammetry, and electrochemical impedance spectroscopy. The results show that the texture properties of the activated carbon fibers were influenced by the activation time. Crucially, the specific surface area, total pore volume, and mesopore volume ratio of the RACF with a 70-min activation time (RACF-70) were 2150 m²/g, 1.03 cm³/g and 31.1%, respectively. Further, electrochemical performance analysis found that the specific capacitance of RACF-70 increased from 82.6 to 103.6 F/g (at 2 mA/cm²). The overall high specific capacitance and low resistance of the RACFs were probably influenced by the pore structure that developed outstanding impedance properties. The results of this work demonstrate that RACFs have promising application value as performance enhancing EDLC electrode materials. Full article

(This article belongs to the Special Issue Materials for Energy Applications 2.0)

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11 pages, 2600 KiB

Open AccessArticle

Hydrogen Production through Catalytic Water Splitting Using Liquid-Phase Plasma over Bismuth Ferrite Catalyst

by Kyong-Hwan Chung, Hyun-Hak Jung, Sun-Jae Kim, Young-Kwon Park, Sang-Chai Kim and Sang-Chul Jung

Int. J. Mol. Sci. 2021, 22(24), 13591; https://doi.org/10.3390/ijms222413591 - 18 Dec 2021

Cited by 10 | Viewed by 2894

Abstract

This study examined the H₂ production characteristics from a decomposition reaction using liquid-phase plasma with a bismuth ferrite catalyst. The catalyst was prepared using a sol–gel reaction method. The physicochemical and optical properties of bismuth ferrite were analyzed. H₂ production was [...] Read more.

This study examined the H₂ production characteristics from a decomposition reaction using liquid-phase plasma with a bismuth ferrite catalyst. The catalyst was prepared using a sol–gel reaction method. The physicochemical and optical properties of bismuth ferrite were analyzed. H₂ production was carried out from a distilled water and aqueous methanol solution by direct irradiation via liquid-phase plasma. The catalyst absorbed visible-light over 610 nm. The measured bandgap of the bismuth ferrite was approximately 2.0 eV. The liquid-phase plasma emitted UV and visible-light simultaneously according to optical emission spectrometry. Bismuth ferrite induced a higher H₂ production rate than the TiO₂ photocatalyst because it responds to both UV and visible light generated from the liquid-phase plasma. Full article

(This article belongs to the Special Issue Materials for Energy Applications 2.0)

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Review

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66 pages, 12302 KiB

Open AccessReview

Paving the Way to the Fuel of the Future—Nanostructured Complex Hydrides

by Cezar Comanescu

Int. J. Mol. Sci. 2023, 24(1), 143; https://doi.org/10.3390/ijms24010143 - 21 Dec 2022

Cited by 12 | Viewed by 2856

Abstract

Hydrides have emerged as strong candidates for energy storage applications and their study has attracted wide interest in both the academic and industry sectors. With clear advantages due to the solid-state storage of hydrogen, hydrides and in particular complex hydrides have the ability [...] Read more.

Hydrides have emerged as strong candidates for energy storage applications and their study has attracted wide interest in both the academic and industry sectors. With clear advantages due to the solid-state storage of hydrogen, hydrides and in particular complex hydrides have the ability to tackle environmental pollution by offering the alternative of a clean energy source: hydrogen. However, several drawbacks have detracted this material from going mainstream, and some of these shortcomings have been addressed by nanostructuring/nanoconfinement strategies. With the enhancement of thermodynamic and/or kinetic behavior, nanosized complex hydrides (borohydrides and alanates) have recently conquered new estate in the hydrogen storage field. The current review aims to present the most recent results, many of which illustrate the feasibility of using complex hydrides for the generation of molecular hydrogen in conditions suitable for vehicular and stationary applications. Nanostructuring strategies, either in the pristine or nanoconfined state, coupled with a proper catalyst and the choice of host material can potentially yield a robust nanocomposite to reliably produce H₂ in a reversible manner. The key element to tackle for current and future research efforts remains the reproducible means to store H₂, which will build up towards a viable hydrogen economy goal. The most recent trends and future prospects will be presented herein. Full article

(This article belongs to the Special Issue Materials for Energy Applications 2.0)

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39 pages, 3882 KiB

Open AccessReview

Recent Advances in Inverted Perovskite Solar Cells: Designing and Fabrication

by Jiayan Yang, Xingrui Luo, Yankai Zhou, Yingying Li, Qingqing Qiu and Tengfeng Xie

Int. J. Mol. Sci. 2022, 23(19), 11792; https://doi.org/10.3390/ijms231911792 - 4 Oct 2022

Cited by 16 | Viewed by 6005

Abstract

Inverted perovskite solar cells (PSCs) have been extensively studied by reason of their negligible hysteresis effect, easy fabrication, flexible PSCs and good stability. The certified photoelectric conversion efficiency (PCE) achieved 23.5% owing to the formed lead−sulfur (Pb−S) bonds through the surface sulfidation process [...] Read more.

Inverted perovskite solar cells (PSCs) have been extensively studied by reason of their negligible hysteresis effect, easy fabrication, flexible PSCs and good stability. The certified photoelectric conversion efficiency (PCE) achieved 23.5% owing to the formed lead−sulfur (Pb−S) bonds through the surface sulfidation process of perovskite film, which gradually approaches the performance of traditional upright structure PSCs and indicates their industrial application potential. However, the fabricated devices are severely affected by moisture, high temperature and ultraviolet light due to the application of organic materials. Depending on nitrogen, cost of protection may increase, especially for the industrial production in the future. In addition, the inverted PSCs are found with a series of issues compared with the traditional upright PSCs, such as nonradiative recombination of carriers, inferior stability and costly charge transport materials. Thus, the development of inverted PSCs is systematically reviewed in this paper. The design and fabrication of charge transport materials and perovskite materials, enhancement strategies (e.g., interface modification and doping) and the development of all−inorganic inverted devices are discussed to present the indicator for development of efficient and stable inverted PSCs. Full article

(This article belongs to the Special Issue Materials for Energy Applications 2.0)

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33 pages, 8079 KiB

Open AccessReview

Selection, Preparation and Application of Quantum Dots in Perovskite Solar Cells

by Yankai Zhou, Jiayan Yang, Xingrui Luo, Yingying Li, Qingqing Qiu and Tengfeng Xie

Int. J. Mol. Sci. 2022, 23(16), 9482; https://doi.org/10.3390/ijms23169482 - 22 Aug 2022

Cited by 10 | Viewed by 5104

Abstract

As the third generation of new thin-film solar cells, perovskite solar cells (PSCs) have attracted much attention for their excellent photovoltaic performance. Today, PSCs have reported the highest photovoltaic conversion efficiency (PCE) of 25.5%, which is an encouraging value, very close to the [...] Read more.

As the third generation of new thin-film solar cells, perovskite solar cells (PSCs) have attracted much attention for their excellent photovoltaic performance. Today, PSCs have reported the highest photovoltaic conversion efficiency (PCE) of 25.5%, which is an encouraging value, very close to the highest PCE of the most widely used silicon-based solar cells. However, scholars have found that PSCs have problems of being easily decomposed under ultraviolet (UV) light, poor stability, energy level mismatch and severe hysteresis, which greatly limit their industrialization. As unique materials, quantum dots (QDs) have many excellent properties and have been widely used in PSCs to address the issues mentioned above. In this article, we describe the application of various QDs as additives in different layers of PSCs, as luminescent down-shifting materials, and directly as electron transport layers (ETL), light-absorbing layers and hole transport layers (HTL). The addition of QDs optimizes the energy level arrangement within the device, expands the range of light utilization, passivates defects on the surface of the perovskite film and promotes electron and hole transport, resulting in significant improvements in both PCE and stability. We summarize in detail the role of QDs in PSCs, analyze the perspective and associated issues of QDs in PSCs, and finally offer our insights into the future direction of development. Full article

(This article belongs to the Special Issue Materials for Energy Applications 2.0)

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