Research

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12 pages, 16381 KiB

Open AccessArticle

Morphology-Controlled Synthesis of Hematite Nanocrystals and Their Optical, Magnetic and Electrochemical Performance

by Bangquan Li, Qian Sun, Hongsheng Fan, Ming Cheng, Aixian Shan, Yimin Cui and Rongming Wang

Nanomaterials 2018, 8(1), 41; https://doi.org/10.3390/nano8010041 - 15 Jan 2018

Cited by 10 | Viewed by 5307

Abstract

A series of α-Fe₂O₃ nanocrystals (NCs) with fascinating morphologies, such as hollow nanoolives, nanotubes, nanospindles, and nanoplates, were prepared through a simple template-free hydrothermal synthesis process. The results showed that the morphologies could be easily controlled by SO₄²⁻ [...] Read more.

A series of α-Fe₂O₃ nanocrystals (NCs) with fascinating morphologies, such as hollow nanoolives, nanotubes, nanospindles, and nanoplates, were prepared through a simple template-free hydrothermal synthesis process. The results showed that the morphologies could be easily controlled by SO₄²⁻ and H₂PO₄⁻. Physical property analysis showed that the α-Fe₂O₃ NCs exhibited shape- and size-dependent ferromagnetic and optical behaviors. The absorption band peak of the α-Fe₂O₃ NCs could be tuned from 320 to 610 nm. Furthermore, when applied as electrode material for supercapacitor, the hollow olive-structure exhibited the highest capacitance (285.9 F·g⁻¹) and an excellent long-term cycling stability (93% after 3000 cycles), indicating that it could serve as a candidate electrode material for a supercapacitor. Full article

(This article belongs to the Special Issue Nanomaterials Based Fuel Cells and Supercapacitors)

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15 pages, 3787 KiB

Open AccessArticle

Engineering Ru@Pt Core-Shell Catalysts for Enhanced Electrochemical Oxygen Reduction Mass Activity and Stability

by Ariel Jackson, Alaina Strickler, Drew Higgins and Thomas Francisco Jaramillo

Nanomaterials 2018, 8(1), 38; https://doi.org/10.3390/nano8010038 - 12 Jan 2018

Cited by 34 | Viewed by 7994

Abstract

Improving the performance of oxygen reduction reaction (ORR) electrocatalysts is essential for the commercial efficacy of many renewable energy technologies, including low temperature polymer electrolyte fuel cells (PEFCs). Herein, we report highly active and stable carbon-supported Ru@Pt core-shell nanoparticles (Ru@Pt/C) prepared by a [...] Read more.

Improving the performance of oxygen reduction reaction (ORR) electrocatalysts is essential for the commercial efficacy of many renewable energy technologies, including low temperature polymer electrolyte fuel cells (PEFCs). Herein, we report highly active and stable carbon-supported Ru@Pt core-shell nanoparticles (Ru@Pt/C) prepared by a wet chemical synthesis technique. Through rotating disc electrode testing, the Ru@Pt/C achieves an ORR Pt mass-based activity of 0.50 A mg_Pt⁻¹ at 0.9 V versus the reversible hydrogen electrode (RHE), which exceeds the activity of the state-of-the-art commercial Pt/C catalyst as well as the Department of Energy 2020 PEFC electrocatalyst activity targets for transportation applications. The impact of various synthetic parameters, including Pt to Ru ratios and catalyst pretreatments (i.e., annealing) are thoroughly explored. Pt-based mass activity of all prepared Ru@Pt/C catalysts was found to exceed 0.4 mg_Pt⁻¹ across the range of compositions investigated, with the maximum activity catalyst having a Ru:Pt ratio of 1:1. This optimized composition of Ru@Pt/C catalyst demonstrated remarkable stability after 30,000 accelerated durability cycles (0.6 to 1.0 V vs. RHE at 125 mV s⁻¹), maintaining 85% of its initial mass activity. Scanning transmission electron microscopy energy dispersive spectroscopy (STEM-EDS) analysis at various stages of electrochemical testing demonstrated that the Pt shell can provide sufficient protection against the dissolution of the otherwise unstable Ru core. Full article

(This article belongs to the Special Issue Nanomaterials Based Fuel Cells and Supercapacitors)

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9784 KiB

Open AccessFeature PaperArticle

Self-Supported Ni(P, O)_x·MoO_x Nanowire Array on Nickel Foam as an Efficient and Durable Electrocatalyst for Alkaline Hydrogen Evolution

by Wei Hua, Huanyan Liu, Jian-Gan Wang and Bingqing Wei

Nanomaterials 2017, 7(12), 433; https://doi.org/10.3390/nano7120433 - 06 Dec 2017

Cited by 5 | Viewed by 5031

Abstract

Earth-abundant and low-cost catalysts with excellent electrocatalytic hydrogen evolution reaction (HER) activity in alkaline solution play an important role in the sustainable production of hydrogen energy. In this work, a catalyst of Ni(P, O)_x·MoO_x nanowire array on nickel foam has [...] Read more.

Earth-abundant and low-cost catalysts with excellent electrocatalytic hydrogen evolution reaction (HER) activity in alkaline solution play an important role in the sustainable production of hydrogen energy. In this work, a catalyst of Ni(P, O)_x·MoO_x nanowire array on nickel foam has been prepared via a facile route for efficient alkaline HER. Benefiting from the collaborative advantages of Ni(P, O)_x and amorphous MoO_x, as well as three-dimensional porous conductive nickel scaffold, the hybrid electrocatalyst shows high catalytic activity in 1 M KOH aqueous solution, including a small overpotential of 59 mV at 10 mA cm⁻², a low Tafel slope of 54 mV dec^-1, and excellent cycling stability. Full article

(This article belongs to the Special Issue Nanomaterials Based Fuel Cells and Supercapacitors)

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8042 KiB

Open AccessArticle

Hierarchical Mn₂O₃ Microspheres In-Situ Coated with Carbon for Supercapacitors with Highly Enhanced Performances

by Feilong Gong, Shuang Lu, Lifang Peng, Jing Zhou, Jinming Kong, Dianzeng Jia and Feng Li

Nanomaterials 2017, 7(12), 409; https://doi.org/10.3390/nano7120409 - 23 Nov 2017

Cited by 13 | Viewed by 4707

Abstract

Porous Mn₂O₃ microspheres have been synthesized and in-situ coated with amorphous carbon to form hierarchical C@Mn₂O₃ microspheres by first producing MnCO₃ microspheres in solvothermal reactions, and then annealing at 500 °C. The self-assembly growth of MnCO [...] Read more.

Porous Mn₂O₃ microspheres have been synthesized and in-situ coated with amorphous carbon to form hierarchical C@Mn₂O₃ microspheres by first producing MnCO₃ microspheres in solvothermal reactions, and then annealing at 500 °C. The self-assembly growth of MnCO₃ microspheres can generate hollow structures inside each of the particles, which can act as micro-reservoirs to store biomass-glycerol for generating amorphous carbon onto the surfaces of Mn₂O₃ nanorods consisting of microspheres. The C@Mn₂O₃ microspheres, prepared at 500 °C, exhibit highly enhanced pseudocapacitive performances when compared to the particles after annealed at 400 °C and 600 °C. Specifically, the C@Mn₂O₃ microspheres prepared at 500 °C show high specific capacitances of 383.87 F g⁻¹ at current density of 0.5 A g⁻¹, and excellent cycling stability of 90.47% of its initial value after cycling for 5000 times. The asymmetric supercapacitors assembled with C@Mn₂O₃ microspheres after annealed at 500 °C and activated carbon (AC) show an energy density of up to 77.8 Wh kg⁻¹ at power density of 500.00 W kg⁻¹, and a maximum power density of 20.14 kW kg⁻¹ at energy density of 46.8 Wh kg⁻¹. We can attribute the enhanced electrochemical performances of the materials to their three-dimensional (3D) hierarchical structure in-situ coated with carbon. Full article

(This article belongs to the Special Issue Nanomaterials Based Fuel Cells and Supercapacitors)

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6204 KiB

Open AccessArticle

Enhanced Oxygen Reduction Reaction by In Situ Anchoring Fe₂N Nanoparticles on Nitrogen-Doped Pomelo Peel-Derived Carbon

by Yiqing Wang, Mingyuan Zhu, Gang Wang, Bin Dai, Feng Yu, Zhiqun Tian and Xuhong Guo

Nanomaterials 2017, 7(11), 404; https://doi.org/10.3390/nano7110404 - 22 Nov 2017

Cited by 40 | Viewed by 6039

Abstract

The development of effective oxygen electrode catalysts for renewable energy technologies such as metal-air batteries and fuel cells remains challenging. Here, we prepared a novel high-performance oxygen reduction reaction (ORR) catalyst comprised of Fe₂N nanoparticles (NPs) in situ decorated over an [...] Read more.

The development of effective oxygen electrode catalysts for renewable energy technologies such as metal-air batteries and fuel cells remains challenging. Here, we prepared a novel high-performance oxygen reduction reaction (ORR) catalyst comprised of Fe₂N nanoparticles (NPs) in situ decorated over an N-doped porous carbon derived from pomelo peel (i.e., Fe₂N/N-PPC). The decorated Fe₂N NPs provided large quantities of Fe-N-C bonding catalytic sites. The as-obtained Fe₂N/N-PPC showed superior onset and half-wave potentials (0.966 and 0.891 V, respectively) in alkaline media (0.1 M KOH) compared to commercial Pt/C through a direct four-electron reaction pathway. Fe₂N/N-PPC also showed better stability and methanol tolerance than commercial Pt/C. The outstanding ORR performance of Fe₂N/N-PPC was attributed to its high specific surface area and the synergistic effects of Fe₂N NPs. The utilization of agricultural wastes as a precursor makes Fe₂N/N-PPC an ideal non-precious metal catalyst for ORR applications. Full article

(This article belongs to the Special Issue Nanomaterials Based Fuel Cells and Supercapacitors)

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1970 KiB

Open AccessArticle

Construction of Hierarchical CuO/Cu₂O@NiCo₂S₄ Nanowire Arrays on Copper Foam for High Performance Supercapacitor Electrodes

by Luoxiao Zhou, Ying He, Congpu Jia, Vladimir Pavlinek, Petr Saha and Qilin Cheng

Nanomaterials 2017, 7(9), 273; https://doi.org/10.3390/nano7090273 - 15 Sep 2017

Cited by 40 | Viewed by 8800

Abstract

Hierarchical copper oxide @ ternary nickel cobalt sulfide (CuO/Cu₂O@NiCo₂S₄) core-shell nanowire arrays on Cu foam have been successfully constructed by a facile two-step strategy. Vertically aligned CuO/Cu₂O nanowire arrays are firstly grown on Cu foam [...] Read more.

Hierarchical copper oxide @ ternary nickel cobalt sulfide (CuO/Cu₂O@NiCo₂S₄) core-shell nanowire arrays on Cu foam have been successfully constructed by a facile two-step strategy. Vertically aligned CuO/Cu₂O nanowire arrays are firstly grown on Cu foam by one-step thermal oxidation of Cu foam, followed by electrodeposition of NiCo₂S₄ nanosheets on the surface of CuO/Cu₂O nanowires to form the CuO/Cu₂O@NiCo₂S₄ core-shell nanostructures. Structural and morphological characterizations indicate that the average thickness of the NiCo₂S₄ nanosheets is ~20 nm and the diameter of CuO/Cu₂O core is ~50 nm. Electrochemical properties of the hierarchical composites as integrated binder-free electrodes for supercapacitor were evaluated by various electrochemical methods. The hierarchical composite electrodes could achieve ultrahigh specific capacitance of 3.186 F cm⁻² at 10 mA cm⁻², good rate capability (82.06% capacitance retention at the current density from 2 to 50 mA cm⁻²) and excellent cycling stability, with capacitance retention of 96.73% after 2000 cycles at 10 mA cm⁻². These results demonstrate the significance of optimized design and fabrication of electrode materials with more sufficient electrolyte-electrode interface, robust structural integrity and fast ion/electron transfer. Full article

(This article belongs to the Special Issue Nanomaterials Based Fuel Cells and Supercapacitors)

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2992 KiB

Open AccessFeature PaperArticle

Facile synthesis of Mesoporouscobalt Hexacyanoferrate Nanocubes for High-Performance Supercapacitors

by Zhiyong Zhang, Jian-Gan Wang and Bingqing Wei

Nanomaterials 2017, 7(8), 228; https://doi.org/10.3390/nano7080228 - 21 Aug 2017

Cited by 14 | Viewed by 5403

Abstract

Mesoporous cobalt hexacyanoferrate nanocubes (meso–CoHCF) were prepared for the first time through a facile sacrificial template method. The CoHCF mesostructures possess a high specific surface area of 548.5 m²·g⁻¹ and a large amount of mesopores, which enable fast mass transport [...] Read more.

Mesoporous cobalt hexacyanoferrate nanocubes (meso–CoHCF) were prepared for the first time through a facile sacrificial template method. The CoHCF mesostructures possess a high specific surface area of 548.5 m²·g⁻¹ and a large amount of mesopores, which enable fast mass transport of electrolyte and abundant energy storage sites. When evaluated as supercapacitor materials, the meso–CoHCF materials exhibit a high specific capacitance of 285 F·g⁻¹, good rate capability and long cycle life with capacitance retention of 92.9% after 3000 cycles in Na₂SO₄ aqueous electrolyte. The excellent electrochemical properties demonstrate the rational preparation of mesoporous prussian blue and its analogues for energy storage applications. Full article

(This article belongs to the Special Issue Nanomaterials Based Fuel Cells and Supercapacitors)

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27750 KiB

Open AccessArticle

Stepwise Splitting Growth and Pseudocapacitive Properties of Hierarchical Three-Dimensional Co₃O₄ Nanobooks

by Huilong Chen, Shuang Lu, Feilong Gong, Huanzhen Liu and Feng Li

Nanomaterials 2017, 7(4), 81; https://doi.org/10.3390/nano7040081 - 10 Apr 2017

Cited by 12 | Viewed by 4745

Abstract

Three-dimensional hierarchical Co₃O₄ nanobooks have been synthesized successfully on a large scale by calcining orthorhombic Co(CO₃)_0.5(OH)·0.11H₂O precursors with identical morphologies. Based on the influence of reaction time and urea concentration on the nanostructures of [...] Read more.

Three-dimensional hierarchical Co₃O₄ nanobooks have been synthesized successfully on a large scale by calcining orthorhombic Co(CO₃)_0.5(OH)·0.11H₂O precursors with identical morphologies. Based on the influence of reaction time and urea concentration on the nanostructures of the precursors, a stepwise splitting growth mechanism can be proposed to understand the formation of the 3D nanobooks. The 3D Co₃O₄ nanobooks exhibit excellent pseudocapacitive performances with specific capacitances of 590, 539, 476, 453, and 421 F/g at current densities of 0.5, 1, 2, 4, and 8 A/g, respectively. The devices can retain ca. 97.4% of the original specific capacitances after undergoing charge–discharge cycle tests 1000 times continuously at 4 A/g. Full article

(This article belongs to the Special Issue Nanomaterials Based Fuel Cells and Supercapacitors)

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1578 KiB

Open AccessArticle

Formation of Platinum Catalyst on Carbon Black Using an In‐Liquid Plasma Method for Fuel Cells

by Yoshiyuki Show and Yutaro Ueno

Nanomaterials 2017, 7(2), 31; https://doi.org/10.3390/nano7020031 - 31 Jan 2017

Cited by 19 | Viewed by 5310

Abstract

Platinum (Pt) catalyst was formed on the surface of carbon black using an in‐liquid plasma method. The formed Pt catalyst showed the average particle size of 4.1 nm. This Pt catalyst was applied to a polymer electrolyte membrane fuel cell (PEMFC). The PEMFC [...] Read more.

Platinum (Pt) catalyst was formed on the surface of carbon black using an in‐liquid plasma method. The formed Pt catalyst showed the average particle size of 4.1 nm. This Pt catalyst was applied to a polymer electrolyte membrane fuel cell (PEMFC). The PEMFC showed an open voltage of 0.85 V and a maximum output power density of 216 mW/cm2. Full article

(This article belongs to the Special Issue Nanomaterials Based Fuel Cells and Supercapacitors)

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3489 KiB

Open AccessArticle

Electrochemical and Capacitive Properties of Carbon Dots/Reduced Graphene Oxide Supercapacitors

by Yong-Qiang Dang, Shao-Zhao Ren, Guoyang Liu, Jiangtao Cai, Yating Zhang and Jieshan Qiu

Nanomaterials 2016, 6(11), 212; https://doi.org/10.3390/nano6110212 - 14 Nov 2016

Cited by 53 | Viewed by 8508

Abstract

There is much recent interest in graphene-based composite electrode materials because of their excellent mechanical strengths, high electron mobilities, and large specific surface areas. These materials are good candidates for applications in supercapacitors. In this work, a new graphene-based electrode material for supercapacitors [...] Read more.

There is much recent interest in graphene-based composite electrode materials because of their excellent mechanical strengths, high electron mobilities, and large specific surface areas. These materials are good candidates for applications in supercapacitors. In this work, a new graphene-based electrode material for supercapacitors was fabricated by anchoring carbon dots (CDs) on reduced graphene oxide (rGO). The capacitive properties of electrodes in aqueous electrolytes were systematically studied by galvanostatic charge-discharge measurements, cyclic voltammetry, and electrochemical impedance spectroscopy. The capacitance of rGO was improved when an appropriate amount of CDs were added to the material. The CD/rGO electrode exhibited a good reversibility, excellent rate capability, fast charge transfer, and high specific capacitance in 1 M H₂SO₄. Its capacitance was as high as 211.9 F/g at a current density of 0.5 A/g. This capacitance was 74.3% higher than that of a pristine rGO electrode (121.6 F/g), and the capacitance of the CD/rGO electrode retained 92.8% of its original value after 1000 cycles at a CDs-to-rGO ratio of 5:1. Full article

(This article belongs to the Special Issue Nanomaterials Based Fuel Cells and Supercapacitors)

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Review

Jump to: Research

4336 KiB

Open AccessReview

NiCo₂O₄-Based Supercapacitor Nanomaterials

by Chenggang Wang, E Zhou, Weidong He, Xiaolong Deng, Jinzhao Huang, Meng Ding, Xianqi Wei, Xiaojing Liu and Xijin Xu

Nanomaterials 2017, 7(2), 41; https://doi.org/10.3390/nano7020041 - 15 Feb 2017

Cited by 136 | Viewed by 14832

Abstract

In recent years, the research on supercapacitors has ushered in an explosive growth, which mainly focuses on seeking nano-/micro-materials with high energy and power densities. Herein, this review will be arranged from three aspects. We will summarize the controllable architectures of spinel NiCo [...] Read more.

In recent years, the research on supercapacitors has ushered in an explosive growth, which mainly focuses on seeking nano-/micro-materials with high energy and power densities. Herein, this review will be arranged from three aspects. We will summarize the controllable architectures of spinel NiCo₂O₄ fabricated by various approaches. Then, we introduce their performances as supercapacitors due to their excellent electrochemical performance, including superior electronic conductivity and electrochemical activity, together with the low cost and environmental friendliness. Finally, the review will be concluded with the perspectives on the future development of spinel NiCo₂O₄ utilized as the supercapacitor electrodes. Full article

(This article belongs to the Special Issue Nanomaterials Based Fuel Cells and Supercapacitors)

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