MOF assisted synthesis of new porous nickel phosphate nanorods as an advanced electrode material for energy storage application

Journal of Solid State Electrochemistry - A highly uniform porous 1-D nickel pyrophosphate (PNP) nanorods have been developed by a simple and green approach for the first time and served as...     

Pechini synthesis and characterization of molybdenum carbide and nickel molybdenum carbide

Carbides, such as η-Ni₆Mo₆C, are considered as low-cost substitutes for noble metal catalysts for present applications in hydrodesulfurization and for a possible future sulfur-tolerant fuel cell anode catalyst. Most synthesis methods set the carbon content of the carbides by a carbon-based atmosphere or solid carbon in the synthesis. We show here that β-Mo₂C and η-Ni₆Mo₆C can be synthesized using a Pechini process, simply by heating metal acetates mixed with citric acid and ethylene glycol in one step under H₂ with the only source of carbon being the precursor solution. The β-Mo₂C forms when heating a Mo-acetate precursor at 850 °C. When using Ni- and Mo-acetates, β-Mo₂C forms at 700 °C and lower temperatures, while η-Ni₆Mo₆C forms during heating at 800-900 °C. The η-Ni₆Mo₆C has a surface area of 95.5 m² g⁻¹ and less than 10 m² g⁻¹ when prepared at 800 and 900 °C, respectively. Some Ni₃C, Ni, and NiC impurities are also present in the nanostructured η-Ni₆Mo₆C that was prepared at 900 °C. The η-Ni₆Mo₆C materials made by the Pechini process are compared with those made from a traditional synthesis, using metal organic precursors at 1000 °C under CO/CO₂ mixtures with a carbon activity of 0.011. Our results imply that H₂ and the Pechini process can be used to achieve carbon activities similar to those obtained by methods using gaseous or solid carbon sources.     

Writing ink-promoted synthesis of electrodes with high energy storage performance: A review

As the low-cost commercial product, writing inks(pen ink and Chinese ink) have attracted great attention to fabricate electrochemical electrodes for supercapacitors(SCs) and batteries. Due to the conductive nature deriving from graphitic carbon nanoparticles in ink and strong adhesion, ink can be easily coated onto support to enhance the conductivity, form a porous layer facilitating electrolyte ion diffusion, increase the specific surface area and function as binder and dispersant for other active materials. In this review,the beneficial features of pen ink and Chinese ink are summarized and how these features favor the electrochemical performance is discussed in details. And then, ways to coat ink onto support are described,giving a clear understanding of recent process in this area. Finally, the current challenges and outlook of ink-based electrode are discussed, aiming to offer some basic knowledge and promote wide application and future study of pen ink and Chinese ink in electrochemistry.     

Fluoride based electrode materials for advanced energy storage devices

Energy storage and conversion have become a prime area of research to address both the societal concerns regarding the environment and pragmatic applications such as the powering of an ever increasing cadre of portable electronic devices. This paper reviews the use of fluoride based electrode materials in energy storage devices. The majority of the energy storage and conversion applications for fluorine based materials resides in present and future lithium battery chemistries. The use of fluorides either as coatings or in the formation of oxyfluorides has resulted in a marked increase of the stability and morphological development of electrodes for use in nonaqueous lithium and lithium-ion batteries. Pure fluorides, despite their intrinsic insulative properties, have demonstrated the capability to exhibit exceptional energy densities and have the potential to open the door to future high energy lithium battery technology.     

Nanocomposites induced by two-dimensional titanium carbide nanosheets for highly efficient energy storage

Surface group-rich titanium carbide nanosheets (TCNSs) were successfully fabricated by simply etching Ti₃AlC₂ powders and used as dielectric fillers to promote the dielectric and energy storage performances of poly (vinylidene fluoride-hexafluoropropylene) (PVDF-HFP)-based composites. The PVDF-HFP/TCNS composites realize a high dielectric constant and low dielectric loss of 16.3 and 0.034 at 10² Hz, respectively. Importantly, a high energy storage density (U_e) of 0.367 J cm⁻³ at 900 kV cm⁻¹ and a high energy storage efficiency (η ≥ 78.9%) at a TCNS content of only 0.5 wt% are obtained, which indicates that incorporating TCNS is an efficient route in enhancing U_e while maintaining a high level η of the PVDF-HFP-based composites. According to detailed characterization results, a mechanism related to the reduction of lamellar crystals in the PVDF-HFP matrix is suggested. The above mechanism restricts the movement of polymer chains near the filler-matrix interface and is proposed to be responsible for the outstanding dielectric and energy storage performances. Consequently, this work provides a simple and effective method for fabricating highly efficient energy storage nanocomposites.     

Microwave-assisted synthesis of poly(urea-formaldehyde)/lauryl alcohol phase change energy storage microcapsules

In this study, lauryl alcohol suitable for thermal energy storage applications was microencapsulated in a poly(urea-formaldehyde) shell. The microcapsules were prepared by microwave-assisted in situ polymerization. The morphology and particle size of the poly(urea-formaldehyde)/lauryl alcohol phase change energy storage microcapsules(UF/LA PCESMs) were analyzed using transmission electron microscopy, scanning electron microscopy, atomic force microscopy and dynamic light scattering. The latent heat storage capacities of lauryl alcohol and UF/LA PCESMs were determined using differential scanning calorimetry. The chemical composition of the microcapsules was characterized using Fourier transform infrared spectroscopy. All of the results show that UF/LA PCESMs were synthesized successfully and that the latent heat storage capacity and encapsulation efficiency were 156.0 J/g and 75.0%, respectively, and the diameter of each microcapsule was around 150 nm.     

Synthesis and thermal energy storage properties of a calcium-based room temperature phase change material for energy storage

Journal of Thermal Analysis and Calorimetry - In order to obtain a low-cost, high latent heat and thermostable phase change material with a phase change temperature between 18 and...     

Nanomaterials of high surface energy with exceptional properties in catalysis and energy storage

The properties of nanomaterials for use in catalytic and energy storage applications strongly depends on the nature of their surfaces. Nanocrystals with high surface energy have an open surface structure and possess a high density of low-coordinated step and kink atoms. Possession of such features can lead to exceptional catalytic properties. The current barrier for widespread industrial use is found in the difficulty to synthesise nanocrystals with high-energy surfaces. In this critical review we present a review of the progress made for producing shape-controlled synthesis of nanomaterials of high surface energy using electrochemical and wet chemistry techniques. Important nanomaterials such as nanocrystal catalysts based on Pt, Pd, Au and Fe, metal oxides TiO(2) and SnO(2), as well as lithium Mn-rich metal oxides are covered. Emphasis of current applications in electrocatalysis, photocatalysis, gas sensor and lithium ion batteries are extensively discussed. Finally, a future synopsis about emerging applications is given (139 references).     

Electrochemical and photocatalytic investigation of nickel oxide for energy storage and wastewater treatment

Nickel oxide (NiO) was synthesized via a one-step facile method. X-ray diffraction analysis confirmed the face-centered cubic structure of NiO. The bonding nature and surface purity were confirmed via Fourier-transform infrared spectroscopy. NiO revealed partial spherical morphology with less particle aggregation. The optical bandgap of NiO was found to be 3.75 eV. Cyclic voltammetry revealed well-defined oxidation and reduction peaks for NiO. The charge–discharge curve exhibited specific capacitance of 184.6 F/g at current density of 0.3 A/g. NiO electrode exhibited longer cyclic stability of 93 % up to 1500 cycles. In addition, NiO + H₂O₂ revealed efficient photocatalytic degradation of methylene blue (organic pollutant) under visible-light irradiation with degradation efficiency of ~88 %. These results confirm that nanosized NiO is more suitable for dual application.

     

Valence modulated nickel oxynitride network as integrated bifunctional electrodes for enhanced energy storage

As promising electrode materials,transition metal oxides have attracted considerable attention owing to their excellent performance in electrochemical energy storage.However,their poor conductivity and fragile structure limit their practical application.In this study,a binder-free nickel oxide/oxynitride network(NiON WS)bifunctional electrodes with cation multivalent states that exhibit high energy storage performance were synthesized for the first time.The massive active sites,high specific surface areas,and multiple cation valence states of NiON WS were advantageous for electrochemical redox reaction during its application in supercapacitors(1283.5 mF cm^-2)and lithium-ion batteries(1345.0 mA h g^-1).Particularly,the NiON WS based flexible asymmetric SCs exhibit excellent capacitance and energy densities.First-principle calculations were employed to study the mechanism of the electrochemical performance improvement of NiON WS.This study demonstrates the potential of transition metal oxides electrode with high capacity and activity for electrochemical energy storage and conversion.     

Ultrathin nickel hydroxidenitrate nanoflakes branched on nanowire arrays for high-rate pseudocapacitive energy storage

An ultrathin nickel hydroxidenitrate nanoflake-ZnO nanowire hybrid array has been synthesized by a facile low-cost solution route and has demonstrated high-rate energy storage in pseudocapacitor application with remarkable specific capacitance and excellent cycling stability.     

Thermal conductivity anisotropy of expanded graphite/ chlorate salt composites for thermal energy storage

ABSTRACT

Expanded graphite (EG)/LiCl-NaCl phase change composites are prepared by aqueous solution method with different EG amount and forming pressure to enhance heat conduction for high-temperature latent heat thermal energy storage application. Their microstructure and thermal conductivity are characterized. Results indicate that the composites are uniform and the LiCl-NaCl eutectic is well dispersed in the graphite flakes. Thermal conductivity of the LiCl-NaCl can increase to as much as 40.51 W/(m·K), which is 46 times higher than that of pure eutectic salt. With forming pressure, the thermal conductivities of the samples show anisotropy because of a flattened irregular honeycomb network of graphite. Within certain limits, the greater the forming pressure is, the more pronounced the anisotropy performs. In addition, the formulas to calculate the thermal conductivity in the axial direction and the radial direction are given based on the average rotation angle φ of EG basal plane, and experimental data show that the formula in the radial direction is especially useful for calculating the thermal conductivity.     

Electrical conductivity and electrochemical studies of Cr-doped MoO3 nanoflakes for energy storage applications

Journal of Solid State Electrochemistry - The growing demand for electricity has increased the interest of the researchers towards exploration of energy storing devices (ESDs). With the motif for...     

Water-in-salt electrolytes for high voltage aqueous electrochemical energy storage devices

If were not by their low electrochemical stability, aqueous electrolytes would be the preferred alternative to be used in electrochemical energy storage devices. Their abundance and nontoxicity are key factors for such application, especially in large scale. The development of highly concentrated aqueous electrolytes, so-called water-in-salt electrolytes, has expanded the electrochemical window of aqueous electrolyte up to 3.0 V (whereas salt-in-water electrolytes normally shows up to 1.6 V), showing that water can be an alternative after all. Many devices, ranging from metal-ion batteries to electrochemical capacitors, have been reported recently, making use of such wider electrochemical stability and enhancing devices energy density. Different salts have also been proposed not only to gain in costs but also to improve physicochemical properties.     

Seed-mediated synthesis of dendritic platinum nanostructures with high catalytic activity for aqueous-phase hydrogenation of acetophenone

This work reports a facile and efficient seed-mediated method for the synthesis of dendritic platinum(Pt)nanoparticles(NPs) at low temperatures of 55–60 °C in water, using L-ascorbic acid as a reducing agent and sodium citrate as a capping agent. It is found that the dendritic Pt NPs(10–150 nm) are composed of tiny Pt nanocrystals, which nucleate and grow through the introduced smaller Pt seeds with diameters of 3–5 nm.Further investigation shows that the dendritic Pt nanostructures display excellent catalytic performance in an aqueous-phase aromatic ketone hydrogenation reaction, including:(i) acetophenone conversion rate of 90%, with smaller dendritic Pt NPs(10–46 nm) offering a higher conversion efficiency;(ii) high chemoselectivity toward carbonyl group(90.6%–91.5%), e.g., the selectivity to 1-phenylethanol is ~90.1% with nearly100% acetophenone conversion for 10 nm dendritic Pt NPs within 60 min, under mild reaction conditions(20 °C, 1.5 bar H2 pressure, and 1.5 mol% catalyst). The high catalytic activity, selectivity and stability of the dendritic Pt nanostructures under the organic solvent-free conditions make them promising for many potential applications in green catalytic conversion of hydrophilic biomass derived compounds.     

Experimental study on novel phase change composites for thermal energy storage

Journal of Thermal Analysis and Calorimetry - In this study, beeswax is studied as a phase change material (PCM) to store heat due to its high latent heat. The disadvantages of using beeswax were...     

Thermodynamic insights into n-alkanes phase change materials for thermal energy storage

n-Alkanes have been widely used as phase change materials (PCMs) for thermal energy storage applications because of their exceptional phase transition performance, high chemical stability, long term cyclic stability and non-toxicity. However, the thermodynamic properties, especially heat capacity, of n-alkanes have rarely been comprehensively investigated in a wide temperature range, which would be insufficient for design and utilization of n-alkanes-based thermal energy storage techniques. In this study, the thermal properties of n-alkanes (C₁₈H₃₈-C₂₂H₄₆), such as thermal stability, thermal conductivity, phase transition temperature and enthalpy were systematically studied by different thermal analysis and calorimetry methods, and compared with previous results. Thermodynamic property of these n-alkanes was studied in a wide temperature range from 1.9 K to 370 K using a combined relaxation (Physical Property Measurement System, PPMS), differential scanning and adiabatic calorimetry method, and the corresponding thermodynamic functions, such as entropy and enthalpy, were calculated based on the heat capacity curve fitting. Most importantly, the heat capacities and related thermodynamic functions of n-heneicosane and n-docosane were reported for the first time in this work, as far as we know. This research work would provide accurate and reliable thermodynamic properties for further study of n-alkanes-based PCMs for thermal energy storage applications.     

Body temperature triggered shape-memory polymers with high elastic energy storage capacity

Shape-memory polymers (SMPs) that respond near body temperature are attracting broad interest, especially in the biomedical fields. In this study, the triggering temperature of poly(caprolactone) SMP networks is precisely adjusted by inclusion of non-crystallizable molecular linkers and by variation of prepolymer molecular weight. Longer, non-crystalline linkers and lower molecular weight prepolymers interfere with crystallization, lowering the transition temperature. Networks are prepared with crystallization temperatures that are beneath the human body temperature and yet are above room temperature. Upon cooling such amorphous networks to room temperature, crystallization is sluggish. There, elastomers can be easily strained by several hundred-percent to induce crystallization, thereby fixing strained states. If subsequently heated, programmed SMPs can release significant amounts of stored strain energy (∼3 MJ/m³). SMPs that combine elastic energy storage and exhibit triggering temperatures near the human body temperature could benefit emerging applications in the biomedical space. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2016 , 54, 1397–1404