Molecules

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10 pages, 3328 KiB

Open AccessArticle

Effect of Solvothermal Temperature on Morphology and Supercapacitor Performance of Ni-MOF

by Wanxin Shen, Xiaotian Guo and Huan Pang

Molecules 2022, 27(23), 8226; https://doi.org/10.3390/molecules27238226 - 25 Nov 2022

Cited by 16 | Viewed by 3024

A series of Ni-MOF materials were synthesized via a simple hydrothermal method and can be employed as electrodes for supercapacitors (SCs). Different temperatures were selected to unveil the effect of temperature on the formation, structure, and electrochemical performance of Ni-MOF-x (x = 60, [...] Read more.

A series of Ni-MOF materials were synthesized via a simple hydrothermal method and can be employed as electrodes for supercapacitors (SCs). Different temperatures were selected to unveil the effect of temperature on the formation, structure, and electrochemical performance of Ni-MOF-x (x = 60, 80, 100, and 120). Ni-MOF-80 possessed a larger specific surface area with a cross-network structure formed on its surface. The synthesized Ni-MOF electrode delivered a specific capacity of 30.89 mA h g⁻¹ when the current density reached 1 A g⁻¹ in a three-electrode system. The as-fabricated Ni-MOF materials could be further designed and are expected to deliver satisfactory performance in practice. Full article

(This article belongs to the Special Issue Synthesis of Functional Nanomaterials for Electrochemical Energy Storage)

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9 pages, 1788 KiB

Open AccessCommunication

Unveiling the Effect of Solvents on Crystallization and Morphology of 2D Perovskite in Solvent-Assisted Method

by Yingjie Su, Jianqiang Xue, Anmin Liu, Tingli Ma and Liguo Gao

Molecules 2022, 27(6), 1828; https://doi.org/10.3390/molecules27061828 - 11 Mar 2022

Cited by 4 | Viewed by 2726

Abstract

Controlling the crystallographic orientations of 2D perovskite is regarded as an effective way to improve the efficiency of PSCs based on 2D perovskite. In this paper, five different assistant solvents were selected to unveil the effect of solvents on crystallization and morphology of [...] Read more.

Controlling the crystallographic orientations of 2D perovskite is regarded as an effective way to improve the efficiency of PSCs based on 2D perovskite. In this paper, five different assistant solvents were selected to unveil the effect of solvents on crystallization and morphology of 2D perovskite in a solvent-assisted method. Results demonstrated that the effect of Lewis basicity on the crystallization process was the most important factor for preparing 2D perovskite. The stability of the intermediate, reacted between the solvent and the Pb²⁺, determined the quality of 2D film. The stronger the Lewis basicity was, the more obvious the accurate control effect on the top-down crystallization process of 2D perovskite would be. This could enhance the crystallographic orientation of 2D perovskite. The effect of Lewis basicity played a more important role than other properties of the solvent, such as boiling point and polarity. Full article

(This article belongs to the Special Issue Synthesis of Functional Nanomaterials for Electrochemical Energy Storage)

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10 pages, 3442 KiB

Open AccessArticle

Application of Rhamnolipids as Dispersing Agents for the Fabrication of Composite MnO₂-Carbon Nanotube Electrodes for Supercapacitors

by Wenjuan Yang, Wenyu Liang and Igor Zhitomirsky

Molecules 2022, 27(5), 1659; https://doi.org/10.3390/molecules27051659 - 3 Mar 2022

Cited by 3 | Viewed by 1839

Abstract

The high theoretical capacitance of MnO₂ renders it a promising material for the cathodes of asymmetric supercapacitors. The good dispersion of MnO₂ and conductive additives in a nanocomposite electrode is a key factor for efficient electrode performance. This article describes, for [...] Read more.

The high theoretical capacitance of MnO₂ renders it a promising material for the cathodes of asymmetric supercapacitors. The good dispersion of MnO₂ and conductive additives in a nanocomposite electrode is a key factor for efficient electrode performance. This article describes, for the first time, the application of rhamnolipids (RL) as efficient natural biosurfactants for the fabrication of nanocomposite MnO₂-carbon nanotube electrodes for supercapacitors. RL act as co-dispersants for MnO₂ and carbon nanotubes and facilitate their efficient mixing, which allows for advanced capacitive properties at an active mass of 40 mg cm⁻² in Na₂SO₄ electrolytes. The highest capacitance obtained from the cyclic voltammetry data at a scan rate of 2 mV s⁻¹ is 8.10 F cm⁻² (202.6 F g⁻¹). The highest capacitance obtained from the galvanostatic charge–discharge data at a current density of 3 mA cm⁻² is 8.65 F cm⁻² (216.16 F g⁻¹). The obtained capacitances are higher than the capacitances of MnO₂-based electrodes of the same active mass reported in the literature. The approach developed in this investigation is simple compared to other techniques used for the fabrication of electrodes with high active mass. It offers advantages of using a biocompatible RL biosurfactant. Full article

(This article belongs to the Special Issue Synthesis of Functional Nanomaterials for Electrochemical Energy Storage)

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10 pages, 2158 KiB

Open AccessArticle

Zinc-Guided 3D Graphene for Thermally Chargeable Supercapacitors to Harvest Low-Grade Heat

by Qi Wang, Pengyuan Liu, Fanyu Zhou, Lei Gao, Dandan Sun, Yuhang Meng and Xuebin Wang

Molecules 2022, 27(4), 1239; https://doi.org/10.3390/molecules27041239 - 12 Feb 2022

Cited by 3 | Viewed by 2160

Abstract

Low-grade heat energy recycling is the key technology of waste-heat utilization, which needs to be improved. Here, we use a zinc-assisted solid-state pyrolysis route to prepare zinc-guided 3D graphene (ZnG), a 3D porous graphene with the interconnected structure. The obtained ZnG, with a [...] Read more.

Low-grade heat energy recycling is the key technology of waste-heat utilization, which needs to be improved. Here, we use a zinc-assisted solid-state pyrolysis route to prepare zinc-guided 3D graphene (ZnG), a 3D porous graphene with the interconnected structure. The obtained ZnG, with a high specific surface area of 1817 m²·g⁻¹ and abundant micropores and mesopores, gives a specific capacitance of 139 F·g⁻¹ in a neutral electrolyte when used as electrode material for supercapacitors. At a high current density of 8 A·g⁻¹, the capacitance retention is 93% after 10,000 cycles. When ZnG is used for thermally chargeable supercapacitors, the thermoelectric conversion of the low-grade heat energy is successfully realized. This work thus provides a demonstration for low-grade heat energy conversion. Full article

(This article belongs to the Special Issue Synthesis of Functional Nanomaterials for Electrochemical Energy Storage)

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8 pages, 396 KiB

Open AccessArticle

Research of Nanomaterials as Electrodes for Electrochemical Energy Storage

by Nataliya N. Yazvinskaya, Mikhail S. Lipkin, Nikolay E. Galushkin and Dmitriy N. Galushkin

Molecules 2022, 27(3), 837; https://doi.org/10.3390/molecules27030837 - 27 Jan 2022

Cited by 2 | Viewed by 2672

Abstract

This paper has experimentally proved that hydrogen accumulates in large quantities in metal-ceramic and pocket electrodes of alkaline batteries during their operation. Hydrogen accumulates in the electrodes in an atomic form. After the release of hydrogen from the electrodes, a powerful exothermic reaction [...] Read more.

This paper has experimentally proved that hydrogen accumulates in large quantities in metal-ceramic and pocket electrodes of alkaline batteries during their operation. Hydrogen accumulates in the electrodes in an atomic form. After the release of hydrogen from the electrodes, a powerful exothermic reaction of atomic hydrogen recombination with a large energy release occurs. This exothermic reaction is the cause of thermal runaway in alkaline batteries. For the KSL-15 battery, the gravimetric capacity of sintered nickel matrix of the oxide-nickel electrode, as hydrogen storage, is 20.2 wt%, and cadmium electrode is 11.5 wt%. The stored energy density in the metal-ceramic matrix of the oxide-nickel electrode of the battery KSL-15 is 44 kJ/g, and in the cadmium electrode it is 25 kJ/g. The similar values for the KPL-14 battery are as follows. The gravimetric capacity of the active substance of the pocket oxide-nickel electrode, as a hydrogen storage, is 22 wt%, and the cadmium electrode is 16.9 wt%. The density of the stored energy in the active substance oxide-nickel electrode is 48 kJ/g, and in the active substance of the cadmium electrode it is 36.8 kJ/g. The obtained results of the accumulation of hydrogen energy in the electrodes by the electrochemical method are three times higher than any previously obtained results using the traditional thermochemical method. Full article

(This article belongs to the Special Issue Synthesis of Functional Nanomaterials for Electrochemical Energy Storage)

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11 pages, 5748 KiB

Open AccessArticle

Preparation of Hollow Core–Shell Fe₃O₄/Nitrogen-Doped Carbon Nanocomposites for Lithium-Ion Batteries

by Jie Wang, Qin Hu, Wenhui Hu, Wei Zhu, Ying Wei, Kunming Pan, Mingbo Zheng and Huan Pang

Molecules 2022, 27(2), 396; https://doi.org/10.3390/molecules27020396 - 8 Jan 2022

Cited by 17 | Viewed by 2765

Abstract

Iron oxides are potential electrode materials for lithium-ion batteries because of their high theoretical capacities, low cost, rich resources, and their non-polluting properties. However, iron oxides demonstrate large volume expansion during the lithium intercalation process, resulting in the electrode material being crushed, which [...] Read more.

Iron oxides are potential electrode materials for lithium-ion batteries because of their high theoretical capacities, low cost, rich resources, and their non-polluting properties. However, iron oxides demonstrate large volume expansion during the lithium intercalation process, resulting in the electrode material being crushed, which always results in poor cycle performance. In this paper, to solve the above problem, iron oxide/carbon nanocomposites with a hollow core–shell structure were designed. Firstly, an Fe₂O₃@polydopamine nanocomposite was prepared using an Fe₂O₃ nanocube and dopamine hydrochloride as precursors. Secondly, an Fe₃O₄@N-doped C composite was obtained by means of further carbonization treatment. Finally, Fe₃O₄@void@N-Doped C-x composites with core–shell structures with different void sizes were obtained by means of Fe₃O₄ etching. The effect of the etching time on the void size was studied. The electrochemical properties of the composites when used as lithium-ion battery materials were studied in more detail. The results showed that the sample that was obtained via etching for 5 h using 2 mol L⁻¹ HCl solution at 30 °C demonstrated better electrochemical performance. The discharge capacity of the Fe₃O₄@void@N-Doped C-5 was able to reach up to 1222 mA g h⁻¹ under 200 mA g⁻¹ after 100 cycles. Full article

(This article belongs to the Special Issue Synthesis of Functional Nanomaterials for Electrochemical Energy Storage)

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12 pages, 4500 KiB

Open AccessArticle

Sodium-Vanadium Bronze Na₉V₁₄O₃₅: An Electrode Material for Na-Ion Batteries

by Maria A. Kirsanova, Alexey S. Akmaev, Mikhail V. Gorbunov, Daria Mikhailova and Artem M. Abakumov

Molecules 2022, 27(1), 86; https://doi.org/10.3390/molecules27010086 - 24 Dec 2021

Cited by 1 | Viewed by 2893

Abstract

Na₉V₁₄O₃₅ (η-Na_xV₂O₅) has been synthesized via solid-state reaction in an evacuated sealed silica ampoule and tested as electroactive material for Na-ion batteries. According to powder X-ray diffraction, electron diffraction and atomic resolution [...] Read more.

Na₉V₁₄O₃₅ (η-Na_xV₂O₅) has been synthesized via solid-state reaction in an evacuated sealed silica ampoule and tested as electroactive material for Na-ion batteries. According to powder X-ray diffraction, electron diffraction and atomic resolution scanning transmission electron microscopy, Na₉V₁₄O₃₅ adopts a monoclinic structure consisting of layers of corner- and edge-sharing VO₅ tetragonal pyramids and VO₄ tetrahedra with Na cations positioned between the layers, and can be considered as sodium vanadium(IV,V) oxovanadate Na₉V₁₀^4.1+O₁₉(V⁵⁺O₄)₄. Behavior of Na₉V₁₄O₃₅ as a positive and negative electrode in Na half-cells was investigated by galvanostatic cycling against metallic Na, synchrotron powder X-ray diffraction and electron energy loss spectroscopy. Being charged to 4.6 V vs. Na⁺/Na, almost 3 Na can be extracted per Na₉V₁₄O₃₅ formula, resulting in electrochemical capacity of ~60 mAh g⁻¹. Upon discharge below 1 V, Na₉V₁₄O₃₅ uptakes sodium up to Na:V = 1:1 ratio that is accompanied by drastic elongation of the separation between the layers of the VO₄ tetrahedra and VO₅ tetragonal pyramids and volume increase of about 31%. Below 0.25 V, the ordered layered Na₉V₁₄O₃₅ structure transforms into a rock-salt type disordered structure and ultimately into amorphous products of a conversion reaction at 0.1 V. The discharge capacity of 490 mAh g⁻¹ delivered at first cycle due to the conversion reaction fades with the number of charge-discharge cycles. Full article

(This article belongs to the Special Issue Synthesis of Functional Nanomaterials for Electrochemical Energy Storage)

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10 pages, 3228 KiB

Open AccessArticle

One-Pot Synthesis of Nitrogen-Doped TiO₂ with Supported Copper Nanocrystalline for Photocatalytic Environment Purification under Household White LED Lamp

by Yixiao Pan, Yifei Wang, Shimiao Wu, Yating Chen, Xiangrong Zheng and Ning Zhang

Molecules 2021, 26(20), 6221; https://doi.org/10.3390/molecules26206221 - 14 Oct 2021

Cited by 4 | Viewed by 1894

Abstract

Developing efficient and cheap photocatalysts that are sensitive to indoor light is promising for the practical application of photocatalysis technology. Here, N-doped TiO₂ photocatalyst with loaded Cu crystalline cocatalyst is synthesized by a simple one-pot method. The structure is confirmed by transmission [...] Read more.

Developing efficient and cheap photocatalysts that are sensitive to indoor light is promising for the practical application of photocatalysis technology. Here, N-doped TiO₂ photocatalyst with loaded Cu crystalline cocatalyst is synthesized by a simple one-pot method. The structure is confirmed by transmission electron microscopy and X-ray photoelectron spectroscopy analysis, which exhibit that Cu metal nanocrystalline is uniformly deposited on the surface of N-doped TiO₂ material. UV-Vis absorption spectra illustrate that the modified samples possess favorable visible light absorption properties and suppressed-electron hole separation. The as-fabricated Cu-loaded N-TiO₂ materials show high activity in photocatalytic decomposing isopropanol and inactivating E. coli under the irradiation of a household white LED lamp. The developed synthetic strategy and photocatalytic materials reported here are promising for indoor environment purification. Full article

(This article belongs to the Special Issue Synthesis of Functional Nanomaterials for Electrochemical Energy Storage)

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8 pages, 4935 KiB

Open AccessArticle

Au Modified F-TiO₂ for Efficient Photocatalytic Synthesis of Hydrogen Peroxide

by Lijuan Li, Bingdong Li, Liwei Feng, Xiaoqiu Zhang, Yuqian Zhang, Qiannan Zhao, Guifu Zuo and Xianguang Meng

Molecules 2021, 26(13), 3844; https://doi.org/10.3390/molecules26133844 - 24 Jun 2021

Cited by 10 | Viewed by 2728

Abstract

In this work, Au-modified F-TiO₂ is developed as a simple and efficient photocatalyst for H₂O₂ production under ultraviolet light. The Au/F-TiO₂ photocatalyst avoids the necessity of adding fluoride into the reaction medium for enhancing H₂O₂ [...] Read more.

In this work, Au-modified F-TiO₂ is developed as a simple and efficient photocatalyst for H₂O₂ production under ultraviolet light. The Au/F-TiO₂ photocatalyst avoids the necessity of adding fluoride into the reaction medium for enhancing H₂O₂ synthesis, as in a pure TiO₂ reaction system. The F⁻ modification inhibits the H₂O₂ decomposition through the formation of the ≡Ti–F complex. Au is an active cocatalyst for photocatalytic H₂O₂ production. We compared the activity of TiO₂ with F⁻ modification and without F⁻ modification in the presence of Au, and found that the H₂O₂ production rate over Au/F-TiO₂ reaches four times that of Au/TiO₂. In situ electron spin resonance studies have shown that H₂O₂ is produced by stepwise single-electron oxygen reduction on the Au/F-TiO₂ photocatalyst. Full article

(This article belongs to the Special Issue Synthesis of Functional Nanomaterials for Electrochemical Energy Storage)

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10 pages, 3446 KiB

Open AccessArticle

Highly Efficient Ag₃PO₄/g-C₃N₄ Z-Scheme Photocatalyst for Its Enhanced Photocatalytic Performance in Degradation of Rhodamine B and Phenol

by Mingxi Zhang, Hanxiao Du, Juan Ji, Fengfeng Li, Y. C. Lin, Chenwei Qin, Ze Zhang and Yi Shen

Molecules 2021, 26(7), 2062; https://doi.org/10.3390/molecules26072062 - 3 Apr 2021

Cited by 29 | Viewed by 3017

Abstract

Ag₃PO₄/g-C₃N₄ heterojunctions, with different g-C₃N₄ dosages, were synthesized using an in situ deposition method, and the photocatalytic performance of g-C₃N₄/Ag₃PO₄ heterojunctions was studied under simulated sunlight [...] Read more.

Ag₃PO₄/g-C₃N₄ heterojunctions, with different g-C₃N₄ dosages, were synthesized using an in situ deposition method, and the photocatalytic performance of g-C₃N₄/Ag₃PO₄ heterojunctions was studied under simulated sunlight conditions. The results revealed that Ag₃PO₄/g-C₃N₄ exhibited excellent photocatalytic degradation activity for rhodamine B (Rh B) and phenol under the same light conditions. When the dosage of g-C₃N₄ was 30%, the degradation rate of Rh B at 9 min and phenol at 30 min was found to be 99.4% and 97.3%, respectively. After five cycles of the degradation experiment for Rh B, g-C₃N₄/Ag₃PO₄ still demonstrated stable photodegradation characteristics. The significant improvement in the photocatalytic activity and stability of g-C₃N₄/Ag₃PO₄ was attributed to the rapid charge separation between g-C₃N₄ and Ag₃PO₄ during the Z-scheme charge transfer and recombination process. Full article

(This article belongs to the Special Issue Synthesis of Functional Nanomaterials for Electrochemical Energy Storage)

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