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17 pages, 7944 KiB

Open AccessArticle

Construction of α-MnO₂ on Carbon Fibers Modified with Carbon Nanotubes for Ultrafast Flexible Supercapacitors in Ionic Liquid Electrolytes with Wide Voltage Windows

by Mai Li, Kailan Zhu, Hanxue Zhao, Zheyi Meng, Chunrui Wang and Paul K. Chu

Nanomaterials 2022, 12(12), 2020; https://doi.org/10.3390/nano12122020 - 11 Jun 2022

Cited by 11 | Viewed by 2548

Abstract

In this study, α-MnO₂ and Fe₂O₃ nanomaterials are prepared on a carbon fiber modified with carbon nanotubes to produce the nonbinder core–shell positive (α-MnO₂@CNTs/CC) and negative (Fe₂O₃@CNTs/CC) electrodes that can be operated in [...] Read more.

In this study, α-MnO₂ and Fe₂O₃ nanomaterials are prepared on a carbon fiber modified with carbon nanotubes to produce the nonbinder core–shell positive (α-MnO₂@CNTs/CC) and negative (Fe₂O₃@CNTs/CC) electrodes that can be operated in a wide voltage window in ultrafast asymmetrical flexible supercapacitors. MnO₂ and Fe₂O₃ have attracted wide research interests as electrode materials in energy storage applications because of the abundant natural resources, high theoretical specific capacities, environmental friendliness, and low cost. The electrochemical performance of each electrode is assessed in 1 M Na₂SO₄ and the energy storage properties of the supercapacitors consisting of the two composite electrodes are determined in Na₂SO₄ and EMImBF4 electrolytes in the 2 V and 4 V windows. The 2 V supercapacitor can withstand a large scanning rate of 5000 mV S⁻¹ without obvious changes in the cyclic voltammetry (CV) curves, besides showing a maximum energy density of 57.29 Wh kg⁻¹ at a power density of 833.35 W kg⁻¹. Furthermore, the supercapacitor retains 87.06% of the capacity after 20,000 galvanostatic charging and discharging (GCD) cycles. The 4 V flexible supercapacitor shows a discharging time of 1260 s and specific capacitance of 124.8 F g⁻¹ at a current of 0.5 mA and retains 87.77% of the initial specific capacitance after 5000 GCD cycles. The mechanical robustness and practicality are demonstrated by physical bending and the powering of LED arrays. In addition, the contributions of the active materials to the capacitive properties and the underlying mechanisms are explored and discussed Full article

(This article belongs to the Special Issue Advanced Functional Nanomaterials for Energy Storage Applications)

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16 pages, 3951 KiB

Open AccessArticle

Piezoelectric Effect Enhanced Photocatalytic Activity of Pt/Bi_3.4Gd_0.6Ti₃O₁₂ Plasmonic Photocatalysis

by Fengjuan Liang, Shijun Wu, Zhiwu Chen and Zhenya Lu

Nanomaterials 2022, 12(7), 1170; https://doi.org/10.3390/nano12071170 - 1 Apr 2022

Cited by 9 | Viewed by 2336

Abstract

Novel Pt/Bi_3.4Gd_0.6Ti₃O₁₂ heterojunction was synthesized by a decoration of Pt nanoparticles (PtNPs) on the surface of piezoelectric Bi_3.4Gd_0.6Ti₃O₁₂ (BGTO) through an impregnation process. The photocatalytic, piezo-catalytic, and piezo-photocatalytic activities [...] Read more.

Novel Pt/Bi_3.4Gd_0.6Ti₃O₁₂ heterojunction was synthesized by a decoration of Pt nanoparticles (PtNPs) on the surface of piezoelectric Bi_3.4Gd_0.6Ti₃O₁₂ (BGTO) through an impregnation process. The photocatalytic, piezo-catalytic, and piezo-photocatalytic activities of the Pt/BGTO heterojunction for methyl orange (MO) degradation were investigated under ultrasonic excitation and whole spectrum light irradiation. The internal piezoelectric field of BGTO and a plasmonic effect have been proven important for the photocatalytic activity of the heterojunctions. Pt/BGTO exhibited an optimum photocatalytic degradation performance of 92% for MO in 70 min under irradiation of whole light spectrum and ultrasonic coexcitation, and this value was about 1.41 times higher than the degradation rate under whole spectrum light irradiation alone. The PtNPs in Pt/BGTO heterojunction can absorb the incident light intensively, and induce the collective oscillation of surface electrons due to the surface plasmon resonance (SPR) effect, thus generating “hot” electron–hole pairs. The internal piezoelectric field produced in BGTO by ultrasonic can promote the separation of SPR-induced “hot” charge carriers and facilitate the production of highly reactive oxidation radicals, thus enhancing Pt/BGTO heterojunction′s photocatalytic activity for oxidizing organic dyes. Full article

(This article belongs to the Special Issue Advanced Functional Nanomaterials for Energy Storage Applications)

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14 pages, 2343 KiB

Open AccessArticle

Enhancing the Performance of a Metal-Free Self-Supported Carbon Felt-Based Supercapacitor with Facile Two-Step Electrochemical Activation

by AlBatool A. Abaalkhail, Basheer A. Alshammari, Ghzzai N. Almutairi, Feraih S. Alenazey, Mohammed F. Alotibi, Asma M. Alenad, Abdullah G. Alharbi, Thamer S. Almoneef and Bandar M. AlOtaibi

Nanomaterials 2022, 12(3), 427; https://doi.org/10.3390/nano12030427 - 27 Jan 2022

Cited by 9 | Viewed by 3262

Abstract

Carbon felt (CF) is an inexpensive carbon-based material that is highly conductive and features extraordinary inherent surface area. Using such a metal-free, low-cost material for energy storage applications can benefit their practical implementation; however, only limited success has been achieved using metal-free CF [...] Read more.

Carbon felt (CF) is an inexpensive carbon-based material that is highly conductive and features extraordinary inherent surface area. Using such a metal-free, low-cost material for energy storage applications can benefit their practical implementation; however, only limited success has been achieved using metal-free CF for supercapacitor electrodes. This work thoroughly studies a cost-effective and simple method for activating metal-free self-supported carbon felt. As-received CF samples were first chemically modified with an acidic mixture, then put through a time optimization two-step electrochemical treatment in inorganic salts. The initial oxidative exfoliation process enhances the fiber’s surface area and ultimately introduced oxygen functional groups to the surface, whereas the subsequent reduction process substantially improved the conductivity. We achieved a 205-fold enhancement of capacitance over the as-received CF, with a maximum specific capacitance of 205 Fg⁻¹, while using a charging current density of 23 mAg⁻¹. Additionally, we obtained a remarkable capacitance retention of 78% upon increasing the charging current from 0.4 to 1 Ag⁻¹. Finally, the cyclic stability reached 87% capacitance retention after 2500 cycles. These results demonstrate the potential utility of electrochemically activated CF electrodes in supercapacitor devices. Full article

(This article belongs to the Special Issue Advanced Functional Nanomaterials for Energy Storage Applications)

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12 pages, 2781 KiB

Open AccessArticle

Efficient Dye Contaminant Elimination and Simultaneously Electricity Production via a Bi-Doped TiO₂ Photocatalytic Fuel Cell

by Dong Liu, Chunling Li, Congyue Zhao, Er Nie, Jianqiao Wang, Jun Zhou and Qian Zhao

Nanomaterials 2022, 12(2), 210; https://doi.org/10.3390/nano12020210 - 10 Jan 2022

Cited by 12 | Viewed by 1967

Abstract

TiO₂ develops a higher efficiency when doping Bi into it by increasing the visible light absorption and inhibiting the recombination of photogenerated charges. Herein, a highly efficient Bi doped TiO₂ photoanode was fabricated via a one-step modified sol-gel method and a [...] Read more.

TiO₂ develops a higher efficiency when doping Bi into it by increasing the visible light absorption and inhibiting the recombination of photogenerated charges. Herein, a highly efficient Bi doped TiO₂ photoanode was fabricated via a one-step modified sol-gel method and a screen-printing technique for the anode of photocatalytic fuel cell (PFC). A maximum degradation rate of 91.2% of Rhodamine B (RhB) and of 89% after being repeated 5 times with only 2% lost reflected an enhanced PFC performance and demonstrated an excellent stability under visible-light irradiation. The excellent degradation performance was attributed to the enhanced visible-light response and decreased electron-hole recombination rate. Meanwhile, an excellent linear correlation was observed between the efficient photocurrent of PFC and the chemical oxygen demand of solution when RhB is sufficient. Full article

(This article belongs to the Special Issue Advanced Functional Nanomaterials for Energy Storage Applications)

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14 pages, 3151 KiB

Open AccessArticle

Synthesis of Molybdenum Sulfide/Tellurium Hetero-Composite by a Simple One-Pot Hydrothermal Technique for High-Performance Supercapacitor Electrode Material

by Hem Prakash Karki, Hyojae Kim, Jinmu Jung and Jonghyun Oh

Nanomaterials 2021, 11(9), 2346; https://doi.org/10.3390/nano11092346 - 9 Sep 2021

Cited by 10 | Viewed by 2819

Abstract

It is necessary to investigate effective energy storage devices that can fulfill the requirements of short-term and long-term durable energy outputs. Here, we report a simple one-pot hydrothermal technique through which to fabricate the MoS₂/Te nanocomposite to be used as an [...] Read more.

It is necessary to investigate effective energy storage devices that can fulfill the requirements of short-term and long-term durable energy outputs. Here, we report a simple one-pot hydrothermal technique through which to fabricate the MoS₂/Te nanocomposite to be used as an effective electrode material for high-performance supercapacitors. Comprehensive characterization of the as-fabricated nanomaterial was performed using FESEM, HRTEM, XRD, FTIR, XPS, etc., as well as electrochemical characterizations. The electrochemical characterization of the as-fabricated nanocomposite electrode material showed a high specific capacitance of 402.53 F g⁻¹ from a galvanostatic charge-discharge (GCD) profile conducted at 1 A g⁻¹ current density. The electrode material also showed significant rate performance with high cyclic stability reaching up to 92.30% under 4000 cycles of galvanostatic charge-discharge profile at a current density of 10 A g⁻¹. The highly encouraging results obtained using this simple synthetic approach demonstrate that the hetero-structured nanocomposite of MoS₂/Te electrode material could serve as a promising composite to use in effective supercapacitors or energy storage devices. Full article

(This article belongs to the Special Issue Advanced Functional Nanomaterials for Energy Storage Applications)

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16 pages, 3917 KiB

Open AccessArticle

Controlled Biosynthesis of ZnCdS Quantum Dots with Visible-Light-Driven Photocatalytic Hydrogen Production Activity

by Shiyue Qi, Yahui Miao, Ji Chen, Huichao Chu, Bingyang Tian, Borong Wu, Yanju Li and Baoping Xin

Nanomaterials 2021, 11(6), 1357; https://doi.org/10.3390/nano11061357 - 21 May 2021

Cited by 33 | Viewed by 3453

Abstract

The development of visible-light-responsive photocatalysts with high efficiency, stability, and eco-friendly nature is beneficial to the large-scale application of solar hydrogen production. In this work, the production of biosynthetic ternary ZnCdS photocatalysts (Eg = 2.35–2.72 eV) by sulfate-reducing bacteria (SRB) under mild conditions [...] Read more.

The development of visible-light-responsive photocatalysts with high efficiency, stability, and eco-friendly nature is beneficial to the large-scale application of solar hydrogen production. In this work, the production of biosynthetic ternary ZnCdS photocatalysts (Eg = 2.35–2.72 eV) by sulfate-reducing bacteria (SRB) under mild conditions was carried out for the first time. The huge amount of biogenic S²⁻ and inherent extracellular proteins (EPs) secreted by SRB are important components of rapid extracellular biosynthesis. The ternary ZnCdS QDs at different molar ratios of Zn²⁺and Cd²⁺ from 15:1 to 1:1 were monodisperse spheres with good crystallinity and average crystallite size of 6.12 nm, independent of the molar ratio of Cd²⁺ to Zn²⁺. All the ZnCdS QDs had remarkable photocatalytic activity and stability for hydrogen evolution under visible light, without noble metal cocatalysts. Especially, ZnCdS QDs at Zn/Cd = 3:1 showed the highest H₂ production activity of 3.752 mmol·h⁻¹·g⁻¹. This excellent performance was due to the high absorption of visible light, the high specific surface area, and the lower recombination rate between photoexcited electrons and holes. The adhered inherent EPs on the ZnCdS QDs slowed down the photocorrosion and improved the stability in photocatalytic hydrogen evolution. This study provides a new direction for solar hydrogen production. Full article

(This article belongs to the Special Issue Advanced Functional Nanomaterials for Energy Storage Applications)

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12 pages, 1905 KiB

Open AccessFeature PaperArticle

Ultra-Stable Potassium Ion Storage of Nitrogen-Doped Carbon Nanofiber Derived from Bacterial Cellulose

by Liang Ma, Jinliang Li, Zhibin Li, Yingying Ji, Wenjie Mai and Hao Wang

Nanomaterials 2021, 11(5), 1130; https://doi.org/10.3390/nano11051130 - 27 Apr 2021

Cited by 11 | Viewed by 2731

Abstract

As a promising energy storage system, potassium (K) ion batteries (KIBs) have received extensive attention due to the abundance of potassium resource in the Earth’s crust and the similar properties of K to Li. However, the electrode always presents poor stability for K-ion [...] Read more.

As a promising energy storage system, potassium (K) ion batteries (KIBs) have received extensive attention due to the abundance of potassium resource in the Earth’s crust and the similar properties of K to Li. However, the electrode always presents poor stability for K-ion storage due to the large radius of K-ions. In our work, we develop a nitrogen-doped carbon nanofiber (N-CNF) derived from bacterial cellulose by a simple pyrolysis process, which allows ultra-stable K-ion storage. Even at a large current density of 1 A g⁻¹, our electrode exhibits a reversible specific capacity of 81 mAh g⁻¹ after 3000 cycles for KIBs, with a capacity retention ratio of 71%. To investigate the electrochemical enhancement performance of our N-CNF, we provide the calculation results according to density functional theory, demonstrating that nitrogen doping in carbon is in favor of the K-ion adsorption during the potassiation process. This behavior will contribute to the enhancement of electrochemical performance for KIBs. In addition, our electrode exhibits a low voltage plateau during the potassiation–depotassiation process. To further evaluate this performance, we calculate the “relative energy density” for comparison. The results illustrate that our electrode presents a high “relative energy density”, indicating that our N-CNF is a promising anode material for KIBs. Full article

(This article belongs to the Special Issue Advanced Functional Nanomaterials for Energy Storage Applications)

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Review

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27 pages, 3606 KiB

Open AccessReview

Critical Aspects of Various Techniques for Synthesizing Metal Oxides and Fabricating Their Composite-Based Supercapacitor Electrodes: A Review

by Mohd Zahid Ansari, Kang-Min Seo, Soo-Hyun Kim and Sajid Ali Ansari

Nanomaterials 2022, 12(11), 1873; https://doi.org/10.3390/nano12111873 - 30 May 2022

Cited by 34 | Viewed by 3269

Abstract

Supercapacitors (SCs) have attracted attention as an important energy source for various applications owing to their high power outputs and outstanding energy densities. The electrochemical performance of an SC device is predominantly determined by electrode materials, and thus, the selection and synthesis of [...] Read more.

Supercapacitors (SCs) have attracted attention as an important energy source for various applications owing to their high power outputs and outstanding energy densities. The electrochemical performance of an SC device is predominantly determined by electrode materials, and thus, the selection and synthesis of the materials are crucial. Metal oxides (MOs) and their composites are the most widely used pseudocapacitive SC electrode materials. The basic requirements for fabricating high-performance SC electrodes include synthesizing and/or chemically modifying unique conducting nanostructures, optimizing a heterostructure morphology, and generating large-surface-area electroactive sites, all of which predominantly rely on various techniques used for synthesizing MO materials and fabricating MO- and MO-composite-based SC electrodes. Therefore, an SC’s background and critical aspects, the challenges associated with the predominant synthesis techniques (including hydrothermal and microwave-assisted syntheses and chemical-bath and atomic-layer depositions), and resulting electrode electrochemical performances should be summarized in a convenient, accessible report to accelerate the development of materials for industrial SC applications. Therefore, we reviewed the most pertinent studies on these synthesis techniques to provide insight into the most recent advances in synthesizing MOs and fabricating their composite-based SC electrodes as well as to propose research directions for developing MO-based electrodes for applications to next-generation SCs. Full article

(This article belongs to the Special Issue Advanced Functional Nanomaterials for Energy Storage Applications)

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