We present a high-capacity pseudocapacitor based on a hierarchical network architecture consisting of Co3O4 nanowire network (nanonet) coated on a carbon fiber paper. With this tailored architecture, ...the electrode shows ideal capacitive behavior (rectangular shape of cyclic voltammograms) and large specific capacitance (1124 F/g) at high charge/discharge rate (25.34 A/g), still retaining ∼94% of the capacitance at a much lower rate of 0.25 A/g. The much-improved capacity, rate capability, and cycling stability may be attributed to the unique hierarchical network structures, which improves electron/ion transport, enhances the kinetics of redox reactions, and facilitates facile stress relaxation during cycling.
In this study, we report a kind of highly efficient and environmentally friendly cathode based on yeast derived hydrothermal carbon. Different hydrothermal conditions are explored in order to obtain ...the optimal hydrothermal carbon based cathode. Then a kind of one-step synthesis method of yeast based cathode is developed to simplify the experimental scheme. The yeast derived hydrothermal carbon is rich in various atoms including N, P, S, which could provide amounts of active sites for electrochemical reactions in the cathode. Another feature of the hydrothermal carbon based cathode is the mild preparation process in which there is no need of introduction of other surfactants and catalysts. This study is aimed to provide a feasible plan to utilize the biomass derived hydrothermal carbon with unique microstructures, higher heat value, higher carbon content, lower ash content as well as green and inexpensive access. A lithium–oxygen battery with the cathode delivers a high capacity of 21,000 mAh g−1 at 185 mA g−1 in a 1 M LiTFSI/TEGDME electrolyte system. Moreover, the cathode exhibits a good oxygen reduction reaction and oxygen evolution reaction activity. These results suggest that the yeast derived hydrothermal carbon can be efficiently optimized for efficient electrocatalytic reactions in lithium–oxygen batteries.
Abstract: In this work, we propose and fabricate a novel non-aqueous Lithium-oxygen battery with a hydrothermal carbon coated cathode prepared through a facile method, which contains large amounts of active sites and contributes to a significant enhancement in the capacity of battery. Display omitted
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•Local Joule heating between contacted nanoparticles was proposed for catalysis.•Catalyst surface can be precisely heated by local Joule heating for reactions.•Hydrocarbon was ...effectively burned off by the local Joule heating of Sb doped SnO2.•The strategy consumed one order lower energy than the external heating catalysis.
Most industrial catalytic reactions are achieved by external heating and catalysts are entirely heated to offer enough thermal energy to surface active sites. However, there is an inherent drawback that most input energy is dissipated into the bulk while minor is donated to the surface, leading to high energy waste. Here, we proposed a so-called local Joule heating method via passing an electric current through packed catalyst nanoparticles with a large contact resistance, which can generate sufficient heat to target at the surface region. We selected hydrocarbon combustion, a common way to eliminate unburned pollutants, as a probe reaction and used the conductive antimony-doped tin oxide (ATO) as a model catalyst. Compared with traditional external heating, this method consumed one order lower energy input, reduced the macroscopically average temperature for same conversion by ∼100 °C, improved the durability with smaller activity loss within 100 h operation, and suppressed water poisoning effect by ∼60 %. Also, the combustion was sparked in seconds by pulsing electric current into the catalyst bed, allowing an application in prompt treatment of leaked hydrocarbons. The local Joule heating between contacted nanoparticles, which could focus thermal energy on catalyst surface, is prospective to improve catalysis efficiency.
Most researchers usually adopt laboratory experimental methods when studying the effects of water level variations on the concentrations of pollutants. In this study, the data from routine monitoring ...sites in the city of Luoyang, China, are collected and analyzed to verify the results of previous laboratory experiments and to examine whether variations in the water level affect the concentration of pollutants in different locations, particularly that of nitrates. Statistical studies conducted between 2007 and 2011 show a significant variation in the groundwater depth in the Luoyang area. This depth variation clearly affected the groundwater environment in the soil system. This study uses field data to investigate the effects of water table fluctuation on the nitrate content of groundwater. Hydrogeological information and land management data are collected from five monitoring points in Luoyang. The significance of and correlation between the environmental indicators of groundwater depth and soil–water systems are then analyzed using SPSS and Origin software. The results show that the redox potential (E ₕ) and nitrate nitrogen content are strongly correlated with groundwater depth. Significantly negative correlations were found between nitrate nitrogen and ammonium nitrogen concentration, between E ₕand ammonium nitrogen concentration, and between pH and nitrate nitrogen concentration. These results indicate that water table fluctuation affects the soil–water physicochemical properties and further exerts a significant effect on nitrate movement across soil sola.
Rechargeable Li–CO2 batteries offer a sustainable strategy for CO2 utilization and energy storage in an environmentally friendly way. However, the current Li–CO2 batteries are restrained by ...unsatisfactory electrochemical performance and lack of cost-effectiveness in practical application. Thus, developing low-cost and highly effective electrode materials is crucial. Inspired by the concept of high nickel and low cobalt content in the electrode material, ultrafine Co0.1Ni0.9O x nanoparticles decorated on carbon nanotubes (Co0.1Ni0.9O x /CNT) are first developed in this work. Through various characterization techniques, the effects of doping Co2+ cations on the properties and electrochemical performance are systematically studied. At a current density of 100 mA g–1, a battery with the Co0.1Ni0.9O x /CNT electrode delivers a high capacity of 5871.41 mA h g–1 with a Coulombic efficiency of 92.91% and a low overpotential of 3.94 V with an energy efficiency of 68%. At a cutoff capacity of 500 mA h g–1, the battery based on the Co0.1Ni0.9O x /CNT electrode can be easily operated for 50 cycles without the trace of capacity degradation, which is nearly twice more than those with the NiO/CNT and CNT electrodes. Compared with the NiO/CNT electrode, the Co0.1Ni0.9O x /CNT electrode exhibits superior electrocatalytic activity in oxidation and evolution reactions of CO2, which results from doping Co2+ cations in the NiO lattice to improve the p-type electronic conductivity. In addition, the polymer-like discharge products affected by doping Co2+ provide better reaction interfaces, curtailing the overpotential and reducing the life span. The results enlighten new ideas of fabricating high-performance and cost-effective electrode materials for prolonging the cycling life of Li–CO2 batteries toward practical applications.
In this study, a simple and cost-effective dry-pressing method has been used to fabricate a symmetrical solid oxide fuel cell (SOFC) where the dense yttria-stabilized zirconia (YSZ) electrolyte film ...is sandwiched between two symmetrical porous YSZ layers in which La
0.75Sr
0.25Cr
0.5Mn
0.5O
3−
δ
(LSCM) based anode and cathode are incorporated using wet impregnation techniques. The maximum power densities (
P
max) of a single cell with 32
wt.% LSCM impregnated YSZ anode and cathode reach 333 and 265
mW
cm
−2 at 900
°C in dry H
2 and CH
4, respectively. The cell performance is further improved with additional impregnation of a small amount of Sm-doped CeO
2 (SDC) or Ni. When 6
wt.% Ni as catalyst is added to both the anode and cathode,
P
max values of 559 and 547
mW
cm
−2 can be achieved, which are better than with SDC. The effect of Ni on the cathode performance is also investigated by impedance spectra analysis.
Uniform, dense and continuous coatings of La0.8Sr0.2MnO3−δ (LSM) have been successfully deposited on dense/porous La0.6Sr0.4Co0.2Fe0.8O3−δ (LSCF) substrates via a one-step drop-coating process using ...a water-based solution in order to improve the operating stability of solid oxide fuel cell cathode. The processing conditions were optimized by precise control of the composition of infiltrating solution, including chelating agents (glycine, citric acid and ethylene glycol), surfactants (polyvinyl alcohol (PVA), polyethylene glycol (PEG) and polyvinyl pyrrolidone (PVP)) and pH values (5.25, 4.29, 3.01 and 2.09). Ethanol was found to improve the wetting ability of the water-based solution significantly, but unfortunately causing precipitation. The symmetrical and full cells tests demonstrated that both performance and stability of LSCF cathode can be enhanced by surface modification with an optimized LSM film coating, leading to ∼31% reduction in cathodic polarization resistance and ∼45% improvement in power density (without observable degradation) for almost 350 h operation at 750 °C under a constant voltage of 0.7 V.
► A uniform film without nano-particles has been deposited onto porous backbone. ► Leading to 31% reduction in cathodic polarization resistance by film modification. ► Leading to ∼45% and ∼20% improvement in power density and stability (350 h). ► Study the effects of chelating agents, surfactants and pH values on film quality. ► Ethanol can improve wetting ability of aqueous solution but causing precipitation.
A sealant-free solid oxide fuel cell (SOFC) micro-stack was successfully operated inside a liquefied petroleum gas (LPG) flame during cooking. This micro-stack consisted of 4 single cells with ...infiltrated La0.75Sr0.25Cr0.5Mn0.5O3-δ (LSCM) based composite anodes, achieving an open circuit voltage of 0.92 V and a peak power density of 348 mW cm−2. This performance is significantly better than that of stack with its cathode operation outside flame. The results confirmed that the perovskite oxide anode showed good properties of carbon-free, redox-stability, quick-start (less than 1 min) and successful operation under a wide range of oxygen partial pressure. For comparison, the conventional Ni/yttria-stabilized zirconia (Ni/YSZ) anode was prepared and tested under the same conditions, showing an open circuit voltage of 0.915 V and a peak power density of 366 mW cm−2, but obvious carbon deposition, poor stability and slow/difficult-start. The direct flame SOFC (DFFC) with a new configuration and design has a potential for combined heat and power generation for many applications.
► The anode of the DFFC is based on perovskite of La0.75Sr0.25Cr0.5Mn0.5O3-δ. ► The anode was prepared by an infiltration process using an aqueous solution. ► The anode showed carbon-free, redox-stability, quick-start and fuel flexible. ► Combined heat and power generation can be available due to a novel configuration. ► The proposed combined heat and power generation is popularized easily.
In this study, we will report our investigation for La0.75Sr0.25Cr0.5Mn0.5O3−δ (LSCrM) based anodes impregnated with solutions of cobalt (Co) nitrate. A YSZ supported SOFC with pure LSCrM anode and ...La0.7Sr0.3MnO3 (LSM) cathode exhibits the maximum power density (Pmax) of 58.7 and 5.2 mW cm−2 at 850 °C in dry H2 and dry CH4. After the modification of anode with Co nitrate, the Pmax reaches 196.2 mW cm−2 in dry H2 and 28.5 mW cm−2 in dry CH4, about 3.34 times and 5.48 times increase, respectively. These results indicate that Co is also a potential catalyst for LSCrM anode. Moreover, the effect of impregnation amount of catalyst on the cell performance is also evaluated in this study.
•Co catalyst is introduced into the LSCrM anode by impregnation process.•Co shows a good catalytic activity for the oxidation reaction of fuels.•There is not a linear relationship between the cells performance and Co loadings.•Single-layer coating on LSCrM backbone should be obtained in impregnation process.
A novel method for fabricating Ni(NO3)2 solution impregnated YSZ (YSZ: Yttria Stabilized Zirconia) anodes for solid oxide fuel cells (SOFCs) is presented. In order to reduce the impregnation cycles ...and increase the reliability of the YSZ membrane, a YSZ support with a porosity of ∼60% is soaked in a saturated Ni(NO3)2 solution with an increased temperature of 80 °C. The impregnated anode is dried in a vacuum drying device without heating, resulting in a flower-like Ni(NO3)2·6H2O crystal. The formed porous structure is likely to facilitate the impregnating process and considered to be the key to success of the impregnation process with saturated solution. After heating at 700 °C, a novel needle-shaped NiO is presented, which exhibits some advantages including fast preparation, high connectivity, large specific surface area and high operational stability (i.e. high aggregation resistance). For the purpose of comparison, Ni(NO3)2 solution impregnated YSZ anodes prepared through the conventional impregnation process are also characterized under the same conditions.
•A novel method is proposed to prepare Ni impregnated YSZ anode.•A novel needle-shaped Ni is presented after a drying and heating process.•The preparation efficiency for Ni impregnated YSZ anode is improved by 3 times.•The specific surface area of anode is improved by 1.14 times.•The conductivity and operational stability of the anode are improved substantially.
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