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Several compounds have been employed as additives of the V(V) electrolyte for vanadium redox flow battery (VRB) to improve its stability and electrochemical activity. Stability of the V(V) electrolyte with and without additives was investigated with ex-situ heating/cooling treatment over a wide temperature range of −5°C to 60°C. It was observed that methyl orange (MO), Triton X-100 (OP), sodium ligninsulfonate (SL), sodium dodecyl sulfate (SDS) and polyvinyl alcohol (PVA) could significantly improve the stability of the V(V) electrolyte at a wide range of temperature. Their electrochemical behavior in the V(V) electrolyte were further studied by cyclic voltammetry (CV), steady state polarization and electrochemical impedance spectroscopy (EIS). The results showed that the electrochemical activity, including the reversibility of electrode reaction, the diffusivity and polarization resistance of V(V) species and the feasibility of charge transfer of V(V)/V(IV) for the V(V) electrolyte with these additives was all improved compared with the pristine solution.
Electric commercial delivery trucks have the potential to substantially reduce greenhouse gas emissions and pollution and lower per-mile operating and maintenance costs. However, the initial purchase cost of electric vehicles is significantly higher than that of a conventional diesel truck. In addition, electric vehicles have a limited range that may lead to the well known problem commonly known as “range anxiety” due to the lack of nearby recharging stations. From a purely economic perspective, there is a cost tradeoff between low operating and maintenance costs of electric vehicles and their high initial capital costs. In this paper, a deterministic integer programming model is utilized to analyze the competitiveness of commercial electric vehicles. Utilizing realistic assumptions and a wide range of scenarios regarding fleet utilization and fuel efficiency, this research finds breakeven points where electric vehicles become competitive. Results show that under moderate to high utilization levels, the electric vehicles can be competitive.
To increase energy density in lithium-ion batteries (LIBs), novel anode materials are considered based on conversion and alloying mechanisms as these typically possess far higher storage capacity than graphite, however, cyclability of these compounds is typically poor. To overcome these issues, ternary or ‘mixed’ compounds are considered. However, the degree of mixing is often overlooked. Here, Atomic layer deposition (ALD) is used to investigate the influence of the degree of mixing, composition and crystallinity of ZnO–SnO2 ternary materials as LIB anodes. Firstly, two different mixing nanostructures of thin-film ZnO–SnO2 electrodes are constructed: atomically intermixed films where the Zn, Sn and O are mixed at the atomic scale in a single amorphous layer, and nanolaminated films where the ZnO layer and SnO2 layers form a structure with well-defined interfaces. Secondly, by tuning the ratio of ZnO and SnO2, different compositions are obtained. Finally, when ZnO–SnO2 composite films are annealed post-deposition, these can be crystallized to form Zn2SnO4 films. The electrochemical performances of these different variations of ternary ZnO–SnO2 composites were investigated as anode materials in LIBs. This demonstrated the potential of ALD as a research tool in LIBs research and revealed the importance of atomic scale intermixing in these ternary oxides as anodes.
Kinta district, in Perak sate of Malaysia is one of the richest districts that rose from tin mining production and is located strategically in the middle of Perak. The physical evidence of this former tin mining landscape which surrounds Kinta offers a narrative about this past mining history. The glorious years of Kinta occurred during the ‘tin rush’ era between 1884 until 1895. The purpose of this paper is to investigate the mining heritage significance in Kinta district. A critical literature review and field surveys are used as the initial identification of significance places having regard to the remaining surviving evidence that can be promoted for conservation.
Nonstoichiometry and Na incorporation are designed to attain controllable impurity phases Li4P2O7 and Li3PO4 in LiFePO4. The effects of Li4P2O7 and Li3PO4 on structure and electrochemical performance have been investigated. Both Li4P2O7 and Li3PO4 impurities are observed in (Fe, P)-deficient LiFe0.9P0.95O4−δ . With Na+ incorporation, Li4P2O7 phase disappears while Li3PO4 content increases. Proved by X-ray photoelectron spectroscopy, nonstoichiometry and Na-incorporation do not change the chemical state of Fe(II). Our experiments indicate that Li4P2O7 and Li3PO4 show different effects on the electrochemical performance. Li4P2O7 leads to degradation of cyclability, whereas a small amount of Li3PO4 is beneficial for the improvement in capacity and rate capability. The 1% Na-doped LiFe0.9P0.95O4−δ composite exhibits the best electrochemical performance. We ascribe the improvement to the structural stabilization caused by the existence of Li3PO4.
Supercapacitors can deliver high electrical power because of fast ion adsorption/desorption on the surface or surface redox reactions, which, in turn, restrict their energy density. To break surface-storage ceiling and further improve the energy density, here, we develop a cost-effective, layered material made of amorphous metal-organic nanosheets, Ni-p-phenylenediamine (Ni-pPD), with a large intersheet spacing of 1.6 nm for its robust and highly reversible intercalation reaction with tetraethylammonium cations. When coupled with activated carbon cathode, the 230 μm-thick Ni-pPD anode shows a high gravimetric capacitance (259 F g−1) and a high areal capacitance (2.9 F cm−2) at 2 A g−1 within a wide potential window of 2.85 V in the organic electrolyte of tetraethylammonium tetrafluoroborate/acetonitrile. In-situ electrochemical atomic force microscopy reveals that high kinetics at high potentials are attributed to the increased intersheet spacing under large polarization, demonstrating structural advantages of this novel material and its great potential for real-world applications.
Reaction of TiCl4 with L–L [L–L = MeE(CH2)nEMe; E = S or Se, n = 2 or 3, PhE(CH2)2EPh or o-C6H4(EMe)2] in anhydrous n-hexane solution under an N2 atmosphere results in the rapid formation of [TiCl4(L–L)] as yellow, orange or red solids. Analogous bromo and iodo species, [TiX4(L–L)] [X = Br; L–L = MeE(CH2)nEMe or o-C6H4(EMe)2; X = I; L–L = MeSe(CH2)2SeMe or o-C6H4(SeMe)2], were obtained as intense orange or red coloured solids by treatment of TiX4 with L–L in CH2Cl2 solution. Crystallographic studies on [TiCl4{MeS(CH2)2SMe}], [TiCl4{MeS(CH2)3SMe}], [TiCl4{MeSe(CH2)3SeMe}] and [TiCl4{o-C6H4(SeMe)2}] reveal a distorted octahedral arrangement with the coordinated group 16 donor ligand adopting the DL form in the first three cases and the meso form in the fourth example. These studies also reveal a trans influence series of Cl > S ≈ Se on Ti(IV). Solution NMR studies show that the chloro-compounds undergo rapid pyramidal inversion at ambient temperature, while the bromo and iodo species also undergo rapid ligand dissociation/chelate ring-opening. At low temperature these processes are slowed significantly, such that in most of the chloro and bromo species it is possible to identify both the meso and DL invertomers, although ligand exchange is still rapid at 200 K for the iodo species. The potential of these compounds as sources of titanium sulfide or titanium selenide phases via controlled decomposition is also discussed briefly. Finally, the dinuclear species, [Cl3Ti{MeS(CH2)2SMe}]2(μ-O), formed by partial hydrolysis of [TiCl4{MeS(CH2)2SMe}], has also been identified crystallographically.
A novel free-standing type cathode of rechargeable Li–O2 battery composed of only Co3O4 catalyst and Ni foam current collector was designed and realized by a simple chemical deposition reaction. The carbon and binder are no longer necessary for the air electrode. The new air electrode was found to yield obviously higher specific capacity and improved cycle efficiency than the conventional carbon-supported one with almost the highest discharge voltage (2.95 V), the lowest charge voltage (3.44 V), the highest specific capacity (4000 mAh g−1cathode) and the minimum capacity fading among the Li–O2 batteries reported to date. During its discharge process, the discharge products would deposit at the surface and in the pores of the free-standing catalysts. The improved performance was attributed to the abundant available catalytic sites of the particularly structured air electrode, the intimate contact of the discharge product with the catalyst, the effective suppression of the volume expansion in the electrode during subsequent deposition/decomposition of the discharge products, the good adhesion of the catalyst to the current collector, and the open pore system for unrestricted access of the reactant molecules to and from active sites of the catalysts. Furthermore, EIS study pointed out the intrinsic distinction resulting in the different performance between the new electrode and the conventional carbon-supported electrode. The new free-standing type electrode represents a critical step toward developing high-performance Li–O2 batteries.
To further improve the electrochemical performance of MXene materials, MXene(Ti3C2Tx)/α-Fe2O3 nanocomposites are fabricated by a self-assembly method via electrostatic attraction between negatively charged Ti3C2Tx MXenesand positively charged cocoa-like α-Fe2O3 nanoparticles at room temperature. As a negative electrode material, the resulting nanocomposites show excellent electrochemical performance, including a wide operating potential of 1.2 V (−1.2–0 V), a high specific capacitance of 405.4 F g−1 at the current density of 2 A g−1 and a specific capacitance of 197.6 F g−1 even at the current density of 20 A g−1 in 5 M LiCl. In addition, the nanocomposites possess a high cycling stability with 97.7% capacitance retention of the initial capacitance after 2000 cycles. The impressive results indicate that the prepared MXene(Ti3C2Tx)/α-Fe2O3 nanocomposites is a promising negative electrode material for supercapacitor. The self-assemble of MXenes and metal oxides will provide more opportunities for their application in energy storage.
In this study, a hybrid energy storage system (HESS), which combines battery for long-term energy management and supercapacitor for fast dynamic power regulation, is proposed for remote area renewable energy power supply systems. The operation of a passive connected HESS was examined via both theoretical analysis and numerical simulation using Matlab/Simulink. An electric inductor was further introduced to improve the performance of the HESS. An experimental test bench was developed to validate the simulation results. It was demonstrated that the HESS can stabilize energy provision, not only for the intermittent renewable energy (RE), but also for fluctuating load applications.
Mesoporous NiCo2O4 nanoneedles were directly grown on three dimensional (3D) graphene-nickel foam which was prepared by chemical vapor deposition, labeled as NCO/GNF. The structure and morphology of NCO/GNF were investigated by scanning electron microscopy, transmission electron microscopy, X-ray diffraction, element mapping and Raman spectroscopy. The NCO/GNF was employed as electrodes for supercapacitor and methanol electro-oxidation. When used for supercapacitor, the NiCo2O4 nanoneedles exhibit hi exhibit high specific capacitance (1588Fg−1 at 1Ag−1), high power density and energy density (33.88Whkg−1 at 5kWkg−1) as well as long cycling stability. In methanol electro-oxidation, the NiCo2O4 nanoneedles deliver high electro-oxidation activity (93.3Ag−1 at 0.65V) and electro-oxidation stability. The good electrochemical performance of NiCo2O4 nanoneedles is attributed to the 3D structure with large specific area, high conductivity and fast ions/electrons transport.
Fish mortality and hypoxic events occur in many coastal and inland systems and may result from natural or anthropogenically mediated processes. The effects of consequent changes in water biogeochemistry have been investigated for communities of benthic invertebrates and pelagic metazoans. The responses of micro-plankton assemblages, however, have remained largely unstudied. The northern basin of King Harbor, a small embayment within Santa Monica Bay, CA, USA, suffered a massive fish kill in March 2011 as a consequence of acute hypoxia. Dissolved oxygen concentrations < 0.1 ml l−1 were measured in the northern basin of the harbor for several days following the mortality event, and a strong spatial gradient of oxygen was observed from the northern basin to waters outside the harbor. The microplankton community within King Harbor differed significantly from a diatom-dominated community present in neighboring Santa Monica Bay. The latter region appeared unaffected by physicochemical changes, induced by the fish kill, that were observed within the harbor. A trophic shift was observed throughout King Harbor from a photoautotrophic-dominated assemblage to one of heterotrophic forms, with relative abundances of bacterivorous ciliates increasing by more than 80 % in the most impacted part of the harbor. Significant changes in community structure were observed together with dramatically reduced photosynthetic yield of the remaining phytoplankton, indicating severe physiological stress during the extreme hypoxia.
Recycling of plastics is a big issue in terms of environmental sustainability and of waste management. The development of proper technologies for plastic recycling is recognised as a priority. To achieve this aim, the technologies applied in mineral processing can be adapted to recycling systems. In particular, the improvement of comminution technologies is one of the main actions to improve the quality of recycled plastics. The aim of this work is to point out suitable comminution processes for different types of plastic waste. Laboratory comminution tests have been carried out under different conditions of temperature and sample pre-conditioning adopting as refrigerant agents CO2 and liquid nitrogen. The temperature has been monitored by thermocouples placed in the milling chamber. Also different internal mill screens have been adopted. A proper procedure has been set up in order to obtain a selective comminution and a size reduction suitable for further separation treatment. Tests have been performed on plastics coming from medical plastic waste and from a plant for spent lead batteries recycling. Results coming from different mill devices have been compared taking into consideration different indexes for representative size distributions. The results of the performed tests show as cryo-comminution improves the effectiveness of size reduction of plastics, promotes liberation of constituents and increases specific surface size of comminuted particles in comparison to a comminution process carried out at room temperature.
Supercapacitors are high capacitive energy storage devices and find applications where rapid bursts of power are required. Thus materials offering high specific capacitance are of fundamental interest in development of these electrochemical devices. Graphene oxide based nanocomposites are mechanically robust and have interesting electronic properties. These form potential electrode materials efficient for charge storage in supercapacitors. In this perspective, we investigate low cost graphene oxide based nanocomposites as electrode material for supercapacitor. Nanocomposites of graphene oxide and polyvinyl alcohol were synthesized in solution phase by integrating graphene oxide as filler in polyvinyl alcohol matrix. Structural and optical characterizations suggest the formation of graphene oxide and polyvinyl alcohol nanocomposites. These nanocomposites were found to have high specific capacitance, were cyclable, ecofriendly and economical. Our studies suggest that nanocomposites prepared by adding 0.5% wt/wt of graphene oxide in polyvinyl alcohol can be used an efficient electrode material for supercapacitors.
Exploring highly efficient electrocatalysts toward oxygen reduction and evolution reactions are critical for the development of rechargeable zinc–air batteries. As a novel class of electrocatalyst, transition metal nanoparticles encapsulated within nitrogen-doped carbon have been regarded as competitive alternative to replace noble metal electrocatalysts. Herein, we report successful synthesis of high-density iron nanoparticles encapsulated within nitrogen-doped carbon nanoshell (Fe@N–C) by solid-phase precursor׳s pyrolysis of dicyandiamide and ammonium ferric citrate. The resulting Fe@N–C material shows excellent bifunctionality for ORR and OER in alkaline medium compared to state-of-the-art commercial Pt/C and IrO2, which demonstrates high performance and cycling durability in zinc–air battery as efficient oxygen electrocatalyst.
LiNi1-yMyO2 (M = Ga, In and Tl, y = 0.010, 0.025 and 0.050) with small y were synthesized by the combustion method by calcining in an O2 stream at 750 °C for 36 h. XRD analyses, SEM observation and measurement of the variation of discharge capacity with the number of cycles were carried out. All the samples had the R
The transition metal oxides such as LiMn2O4 [1–3], LiCoO2 [4–6] and LiNiO2 [7–16] have been investigated as cathode materials for lithium secondary batteries. LiMn2O4 is very cheap and does not bring about environmental pollution, but its cycling performance is not good. LiCoO2 has a large diffusivity and a high operating voltage, and it can be easily prepared. However, it has a disadvantage that it contains an expensive element Co. LiNiO2 is a very promising cathode material since it has a large discharge capacity and is relatively excellent from the viewpoints of economics and environment. However, its preparation is very difficult as compared with LiCoO2 and LiMn2O4.
Graphene-decorated LiFePO4 composite is synthesized for the first time through in-situ pyrolysis and catalytic graphitization, in which glucose and a trace amount of FeSO4 are employed as the graphene source and catalyst precursor, respectively. Under Ar/H2 (95:5) atmosphere at 750 °C, FeSO4 is thermally reduced to Fe nano-particles (Fe NPs) and glucose is pyrolyzed to carbon fragments first, followed by the in-situ growth of graphene sheets directly on the LiFePO4 nano-particles (LFP NPs) surface through the realignment of carbon fragments under the catalytic effect of the Fe NPs. The graphene sheets not only form a compact and uniform coating layer throughout the LFP NPs, but also stretch out and cross-link into a conducting network around the LFP particles. The LiFePO4@graphene composite displays a high reversible specific capacity of 167.7 mAh g−1 at 0.1C rate, superb rate performance with discharge capacity of 94.3 mAh g−1 at 100C rate and much prolonged cycle life. The remarkable electrochemical improvement is attributed to both electric and ionic conductivity increase as a result of in-situ grown graphene coatings along the LFP surface and the graphene network intrinsically connecting to the LFP particles.
As a potential energy carrier, hydrogen has surged up the priority list as part of broader decarbonization efforts and strategies to build or acquire clean energy economies. Driven by renewable electricity, electrochemical water splitting (WS) promises an ideal long-term, low-carbon way to produce hydrogen, with the ability to tackle various critical energy challenges. To improve the efficiency of electrocatalytic water splitting, electrocatalysts with enhanced conductivity, more exposed active sites, and high intrinsic activity are crucial for decreasing the energy gap for the rate-determining step (RDS) and subsequently improving the conversion efficiency. The incorporation of multidimensional imperfections has been demonstrated to be efficient for modulating the electron distribution and speeding up the electrocatalysis kinetics during electrocatalytic processes and this is now attracting ever-increasing attention. Herein, in this review, we summarize recent progress relating to the regulation of electrical behavior and electron distributions for the optimization of electrocatalytic water-splitting performance via defect engineering. With an emphasis on the beneficial aspects of the hydrogen economy and an in-depth understanding of electron redistribution caused by defect effects, we offer a comprehensive summary of the progress made in the last three to five years. Finally, we also offer future perspectives on the challenges and opportunities relating to water-splitting electrocatalysts in this attractive field.
In the present communication, we report on recent researches for optimizing the performance of a primary organic-based Li-air cell. These researches focus on new processing technologies for a high capacity and high rate capable carbon cathode, and the development of oxygen selective membranes based on polysiloxane and methacrylate–polysiloxane copolymers. These membranes, generally classified as silicone rubbers exhibit high permeability for oxygen and impede water transport from the atmosphere into the Li-air cell and solvent loss from the cell into the atmosphere.
Self-supported gel polymer electrolyte (GPE) was prepared based on copolymer, poly(methyl methacrylate–acrylonitrile–vinyl acetate) (P(MMA–AN–VAc)). The copolymer P(MMA–AN–VAc) was synthesized by emulsion polymerization and the copolymer membrane was prepared through phase inversion. The structure and the performance of the copolymer, the membrane and the GPE were characterized by FTIR, NMR, SEM, XRD, DSC/TG, LSV, CA, and EIS. It is found that the copolymer was formed through the breaking of double bond CC in each monomer. The membrane has low crystallinity and has low glass transition temperature, 39.1°C, its thermal stability is as high as 310°C, and its mechanical strength is improved compared with P(MMA–AN). The GPE is electrochemically stable up to 5.6V (vs. Li/Li+) and its conductivity is 3.48×10−3 Scm−1 at ambient temperature. The lithium ion transference number in the GPE is 0.51 and the conductivity model of the GPE is found to obey the Vogel–Tamman–Fulcher (VTF) equation.
Four type of MnOx (MnO2, Mn2O3, Mn3O4, MnO) hierarchical microspheres assembled by rod-like building blocks are synthesized by a facile hydrothermal process with/without a consequent calcination. The morphology and structure of these hierarchical microspheres are confirmed by XRD, SEM, TEM, HRTEM, XPS and BET measurements. The electrochemical properties of the four hierarchical microspheres are investigated in terms of cycling stability and rate capability. Specific capacities of 240, 396, 271 and 810mAhg−1 can be achieved after 100 cycles at 0.5C for MnO2, Mn2O3, Mn3O4 and MnO, respectively. Even at a high rate of 2C, MnO microspheres can still deliver a reversible capacity of 406mAhg−1. Their superior electrochemical properties might be attributed to the secondary nanostructure in the MnOx microspheres, which could effectively shorten the diffusion pathway of Li+, tolerate the structural stress caused by Li+ insertion/extraction, reduce the side reactions with electrolyte, and restrain the self-aggregation of nanomaterials.
The stability of aluminum and nickel as a current collector was investigated at high potentials in the presence of 0.5M NaPF6 or 0.1M NaBF4 dissolved in EC:DEC (1:1wt.-%). Cyclovoltammetry showed that nickel is unstable under experimental conditions, whereas aluminum is electrochemically stable and can be used as a current collector. The feasibility of sodium-based dual-ion cells was studied with self-prepared graphite electrodes in the presence of both electrolytes. The cells showed a fairly stable reversible specific capacity of 15mAh/g for NaBF4 and 55mAh/g for NaPF6.