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3640 KiB

Open AccessArticle

Ternary CNTs@TiO₂/CoO Nanotube Composites: Improved Anode Materials for High Performance Lithium Ion Batteries

by Mahmoud Madian, Raghunandan Ummethala, Ahmed Osama Abo El Naga, Nahla Ismail, Mark Hermann Rümmeli, Alexander Eychmüller and Lars Giebeler

Materials 2017, 10(6), 678; https://doi.org/10.3390/ma10060678 - 20 Jun 2017

Cited by 18 | Viewed by 6160

Abstract

TiO₂ nanotubes (NTs) synthesized by electrochemical anodization are discussed as very promising anodes for lithium ion batteries, owing to their high structural stability, high surface area, safety, and low production cost. However, their poor electronic conductivity and low Li⁺ ion diffusivity [...] Read more.

TiO₂ nanotubes (NTs) synthesized by electrochemical anodization are discussed as very promising anodes for lithium ion batteries, owing to their high structural stability, high surface area, safety, and low production cost. However, their poor electronic conductivity and low Li⁺ ion diffusivity are the main drawbacks that prevent them from achieving high electrochemical performance. Herein, we report the fabrication of a novel ternary carbon nanotubes (CNTs)@TiO₂/CoO nanotubes composite by a two-step synthesis method. The preparation includes an initial anodic fabrication of well-ordered TiO₂/CoO NTs from a Ti-Co alloy, followed by growing of CNTs horizontally on the top of the oxide films using a simple spray pyrolysis technique. The unique 1D structure of such a hybrid nanostructure with the inclusion of CNTs demonstrates significantly enhanced areal capacity and rate performances compared to pure TiO₂ and TiO₂/CoO NTs, without CNTs tested under identical conditions. The findings reveal that CNTs provide a highly conductive network that improves Li⁺ ion diffusivity, promoting a strongly favored lithium insertion into the TiO₂/CoO NT framework, and hence resulting in high capacity and an extremely reproducible high rate capability. Full article

(This article belongs to the Special Issue Advances in Renewable Energy Conversion Materials)

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6728 KiB

Open AccessArticle

Hollow Palladium Nanoparticles Facilitated Biodegradation of an Azo Dye by Electrically Active Biofilms

by Shafeer Kalathil and Rajib Ghosh Chaudhuri

Materials 2016, 9(8), 653; https://doi.org/10.3390/ma9080653 - 4 Aug 2016

Cited by 6 | Viewed by 6126

Abstract

Dye wastewater severely threatens the environment due to its hazardous and toxic effects. Although many methods are available to degrade dyes, most of them are far from satisfactory. The proposed research provides a green and sustainable approach to degrade an azo dye, methyl [...] Read more.

Dye wastewater severely threatens the environment due to its hazardous and toxic effects. Although many methods are available to degrade dyes, most of them are far from satisfactory. The proposed research provides a green and sustainable approach to degrade an azo dye, methyl orange, by electrically active biofilms (EABs) in the presence of solid and hollow palladium (Pd) nanoparticles. The EABs acted as the electron generator while nanoparticles functioned as the electron carrier agents to enhance degradation rate of the dye by breaking the kinetic barrier. The hollow Pd nanoparticles showed better performance than the solid Pd nanoparticles on the dye degradation, possibly due to high specific surface area and cage effect. The hollow cavities provided by the nanoparticles acted as the reaction centers for the dye degradation. Full article

(This article belongs to the Special Issue Advances in Renewable Energy Conversion Materials)

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2611 KiB

Open AccessArticle

Gas Diffusion Electrodes Manufactured by Casting Evaluation as Air Cathodes for Microbial Fuel Cells (MFC)

by Sandipam Srikanth, Deepak Pant, Xochitl Dominguez-Benetton, Inge Genné, Karolien Vanbroekhoven, Philippe Vermeiren and Yolanda Alvarez-Gallego

Materials 2016, 9(7), 601; https://doi.org/10.3390/ma9070601 - 21 Jul 2016

Cited by 24 | Viewed by 7748

Abstract

One of the most intriguing renewable energy production methods being explored currently is electrical power generation by microbial fuel cells (MFCs). However, to make MFC technology economically feasible, cost efficient electrode manufacturing processes need to be proposed and demonstrated. In this context, VITO [...] Read more.

One of the most intriguing renewable energy production methods being explored currently is electrical power generation by microbial fuel cells (MFCs). However, to make MFC technology economically feasible, cost efficient electrode manufacturing processes need to be proposed and demonstrated. In this context, VITO has developed an innovative electrode manufacturing process based on film casting and phase inversion. The screening and selection process of electrode compositions was done based on physicochemical properties of the active layer, which in turn maintained a close relation with their composition A dual hydrophilic-hydrophobic character in the active layer was achieved with values of ε_hydrophilic up to 10% while ε_TOTAL remained in the range 65 wt % to 75 wt %. Eventually, selected electrodes were tested as air cathodes for MFC in half cell and full cell modes. Reduction currents, up to −0.14 mA·cm²⁻ at −100 mV (vs. Ag/AgCl) were reached in long term experiments in the cathode half-cell. In full MFC, a maximum power density of 380 mW·m⁻² was observed at 100 Ω external load. Full article

(This article belongs to the Special Issue Advances in Renewable Energy Conversion Materials)

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2357 KiB

Open AccessArticle

Heat Transfer Performance of Functionalized Graphene Nanoplatelet Aqueous Nanofluids

by Roberto Agromayor, David Cabaleiro, Angel A. Pardinas, Javier P. Vallejo, Jose Fernandez-Seara and Luis Lugo

Materials 2016, 9(6), 455; https://doi.org/10.3390/ma9060455 - 8 Jun 2016

Cited by 58 | Viewed by 7870

Abstract

The low thermal conductivity of fluids used in many industrial applications is one of the primary limitations in the development of more efficient heat transfer systems. A promising solution to this problem is the suspension of nanoparticles with high thermal conductivities in a [...] Read more.

The low thermal conductivity of fluids used in many industrial applications is one of the primary limitations in the development of more efficient heat transfer systems. A promising solution to this problem is the suspension of nanoparticles with high thermal conductivities in a base fluid. These suspensions, known as nanofluids, have great potential for enhancing heat transfer. The heat transfer enhancement of sulfonic acid-functionalized graphene nanoplatelet water-based nanofluids is addressed in this work. A new experimental setup was designed for this purpose. Convection coefficients, pressure drops, and thermophysical properties of various nanofluids at different concentrations were measured for several operational conditions and the results are compared with those of pure water. Enhancements in thermal conductivity and in convection heat transfer coefficient reach 12% (1 wt %) and 32% (0.5 wt %), respectively. New correlations capable of predicting the Nusselt number and the friction factor of this kind of nanofluid as a function of other dimensionless quantities are developed. In addition, thermal performance factors are obtained from the experimental convection coefficient and pressure drop data in order to assess the convenience of replacing the base fluid with designed nanofluids. Full article

(This article belongs to the Special Issue Advances in Renewable Energy Conversion Materials)

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3844 KiB

Open AccessArticle

Enhancement of Electrochemical Performance of LiMn₂O₄ Spinel Cathode Material by Synergetic Substitution with Ni and S

by Monika Bakierska, Michał Świętosławski, Marta Gajewska, Andrzej Kowalczyk, Zofia Piwowarska, Lucjan Chmielarz, Roman Dziembaj and Marcin Molenda

Materials 2016, 9(5), 366; https://doi.org/10.3390/ma9050366 - 13 May 2016

Cited by 25 | Viewed by 7950

Abstract

Nickel and sulfur doped lithium manganese spinels with a nominal composition of LiMn_2−xNi_xO_4–yS_y (0.1 ≤ x ≤ 0.5 and y = 0.01) were synthesized by a xerogel-type sol-gel method followed by subsequent calcinations at [...] Read more.

Nickel and sulfur doped lithium manganese spinels with a nominal composition of LiMn_2−xNi_xO_4–yS_y (0.1 ≤ x ≤ 0.5 and y = 0.01) were synthesized by a xerogel-type sol-gel method followed by subsequent calcinations at 300 and 650 °C in air. The samples were investigated in terms of physicochemical properties using X-ray powder diffraction (XRD), transmission electron microscopy (EDS-TEM), N₂ adsorption-desorption measurements (N₂-BET), differential scanning calorimetry (DSC), and electrical conductivity studies (EC). Electrochemical characteristics of Li/Li⁺/LiMn_2−xNi_xO_4–yS_y cells were examined by galvanostatic charge/discharge tests (CELL TEST), electrochemical impedance spectroscopy (EIS), and cyclic voltammetry (CV). The XRD showed that for samples calcined at 650 °C containing 0.1 and 0.2 mole of Ni single phase materials of Fd-3m group symmetry and nanoparticles size of around 50 nm were obtained. The energy dispersive X-ray spectroscopy (EDS) mapping confirmed homogenous distribution of nickel and sulfur in the obtained spinel materials. Moreover, it was revealed that the adverse phase transition at around room temperature typical for the stoichiometric spinel was successfully suppressed by Ni and S substitution. Electrochemical results indicated that slight substitution of nickel (x = 0.1) and sulfur (y = 0.01) in the LiMn₂O₄ enhances the electrochemical performance along with the rate capability and capacity retention. Full article

(This article belongs to the Special Issue Advances in Renewable Energy Conversion Materials)

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2480 KiB

Open AccessArticle

Improved Charge Separation in WO₃/CuWO₄ Composite Photoanodes for Photoelectrochemical Water Oxidation

by Danping Wang, Prince Saurabh Bassi, Huan Qi, Xin Zhao, Gurudayal, Lydia Helena Wong, Rong Xu, Thirumany Sritharan and Zhong Chen

Materials 2016, 9(5), 348; https://doi.org/10.3390/ma9050348 - 7 May 2016

Cited by 40 | Viewed by 8814

Abstract

Porous tungsten oxide/copper tungstate (WO₃/CuWO₄) composite thin films were fabricated via a facile in situ conversion method, with a polymer templating strategy. Copper nitrate (Cu(NO₃)₂) solution with the copolymer surfactant Pluronic^®F-127 (Sigma-Aldrich, St. [...] Read more.

Porous tungsten oxide/copper tungstate (WO₃/CuWO₄) composite thin films were fabricated via a facile in situ conversion method, with a polymer templating strategy. Copper nitrate (Cu(NO₃)₂) solution with the copolymer surfactant Pluronic^®F-127 (Sigma-Aldrich, St. Louis, MO, USA, generic name, poloxamer 407) was loaded onto WO₃ substrates by programmed dip coating, followed by heat treatment in air at 550 °C. The Cu²⁺ reacted with the WO₃ substrate to form the CuWO₄ compound. The composite WO₃/CuWO₄ thin films demonstrated improved photoelectrochemical (PEC) performance over WO₃ and CuWO₄ single phase photoanodes. The factors of light absorption and charge separation efficiency of the composite and two single phase films were investigated to understand the reasons for the PEC enhancement of WO₃/CuWO₄ composite thin films. The photocurrent was generated from water splitting as confirmed by hydrogen and oxygen gas evolution, and Faradic efficiency was calculated based on the amount of H₂ produced. This work provides a low-cost and controllable method to prepare WO₃-metal tungstate composite thin films, and also helps to deepen the understanding of charge transfer in WO₃/CuWO₄ heterojunction. Full article

(This article belongs to the Special Issue Advances in Renewable Energy Conversion Materials)

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1527 KiB

Open AccessArticle

Polyols from Microwave Liquefied Bagasse and Its Application to Rigid Polyurethane Foam

by Jiulong Xie, Xianglin Zhai, Chung Yun Hse, Todd F. Shupe and Hui Pan

Materials 2015, 8(12), 8496-8509; https://doi.org/10.3390/ma8125472 - 8 Dec 2015

Cited by 24 | Viewed by 6601

Abstract

Bagasse flour (BF) was liquefied using bi-component polyhydric alcohol (PA) as a solvent and phosphoric acid as a catalyst in a microwave reactor. The effect of BF to solvent ratio and reaction temperatures on the liquefaction extent and characteristics of liquefied products were [...] Read more.

Bagasse flour (BF) was liquefied using bi-component polyhydric alcohol (PA) as a solvent and phosphoric acid as a catalyst in a microwave reactor. The effect of BF to solvent ratio and reaction temperatures on the liquefaction extent and characteristics of liquefied products were evaluated. The results revealed that almost 75% of the raw bagasse was converted into liquid products within 9 min at 150 °C with a BF to solvent ratio of 1/4. The hydroxyl and acid values of the liquefied bagasse (LB) varied with the liquefied conditions. High reaction temperature combining with low BF to solvent ratio resulted in a low hydroxyl number for the LB. The molecular weight and polydispersity of the LB from reactions of 150 °C was lower compared to that from 125 °C. Rigid polyurethane (PU) foams were prepared from LB and methylene diphenyl diisocyanate (MDI), and the structural, mechanical and thermal properties of the PU foam were evaluated. The PU foams prepared using the LB from high reaction temperature showed better physical and mechanical performance in comparison to those from low reaction temperature. The amount of PA in the LB has the ability of increasing thermal stability of LB-PU foams. The results in this study may provide fundamental information on integrated utilizations of sugarcane bagasse via microwave liquefaction process. Full article

(This article belongs to the Special Issue Advances in Renewable Energy Conversion Materials)

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Review

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9507 KiB

Open AccessReview

Optimization of Layered Cathode Materials for Lithium-Ion Batteries

by Christian Julien, Alain Mauger, Karim Zaghib and Henri Groult

Materials 2016, 9(7), 595; https://doi.org/10.3390/ma9070595 - 19 Jul 2016

Cited by 95 | Viewed by 15039

Abstract

This review presents a survey of the literature on recent progress in lithium-ion batteries, with the active sub-micron-sized particles of the positive electrode chosen in the family of lamellar compounds LiMO₂, where M stands for a mixture of Ni, [...] Read more.

This review presents a survey of the literature on recent progress in lithium-ion batteries, with the active sub-micron-sized particles of the positive electrode chosen in the family of lamellar compounds LiMO₂, where M stands for a mixture of Ni, Mn, Co elements, and in the family of yLi₂MnO₃•(1 − y)LiNi_½Mn_½O₂ layered-layered integrated materials. The structural, physical, and chemical properties of these cathode elements are reported and discussed as a function of all the synthesis parameters, which include the choice of the precursors and of the chelating agent, and as a function of the relative concentrations of the M cations and composition y. Their electrochemical properties are also reported and discussed to determine the optimum compositions in order to obtain the best electrochemical performance while maintaining the structural integrity of the electrode lattice during cycling. Full article

(This article belongs to the Special Issue Advances in Renewable Energy Conversion Materials)

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