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1.
The spinel structure of manganese cobalt oxide (Mn,Co)3O4 is one of the most promising coatings for solid oxide fuel cell (SOFC) stainless steel interconnects. The stoichiometric Mn1.5Co1.5O4 composition has properties that are preferable to other Mn/Co ratios, for example a higher conductivity and a thermal expansion coefficient that matches the typical steel substrate. However, previous work showed the Mn/Co ratio changes during operation due to the diffusion of Mn from the substrate. The results presented here are on three coatings with different compositions (namely; pure Co, Mn20Co80, and Mn40Co60) with each coating composition deposited to a thickness of 800 nm, 1500 nm, and 3000 nm. The coatings were applied by DC magnetron sputtering and then machine cut into coupons for isothermal annealing at 800 °C in air using a batch-type furnace for 2, 10, 50, 250, and 1000 h. The morphology, chemical composition (including surface and cross sections of the layers) and structures of the oxides formed were analyzed by SEM, EDS and XRD. Analysis of the element diffusion (Mn, Co, Cr, Fe) shown here points to an optimized coating recipe of Mn40Co60. 相似文献
2.
Xiaofeng ZhangHonghe Zheng Vincent BattagliaRichard L. Axelbaum 《Journal of power sources》2011,196(7):3640-3645
Spinel lithium manganese oxide LiMn2O4 powders were synthesized by a flame-assisted spray technology (FAST) with a precursor solution consisting of stoichiometric amounts of LiNO3 and Mn(NO3)2·4H2O dissolved in methanol. The as-synthesized LiMn2O4 particles were non-agglomerated, and nanocrystalline. A small amount of Mn3O4was detected in the as-synthesized powder due to the decomposition of spinel LiMn2O4 at the high flame temperature. The impurity phase was removed with a post-annealing heat-treatment wherein the grain size of the annealed powder was 33 nm. The charge/discharge curves of both powders matched the characteristic plateaus of spinel LiMn2O4 at 3 V and 4 V vs. Li. However, the annealed powder showed a higher initial discharge capacity of 115 mAh g−1 at 4 V. The test cell with annealed powder showed good rate capability between a voltage of 3.0 and 4.3 V and a first cycle coulombic efficiency of 96%. The low coulombic efficiency from capacity fading may be due to oxygen defects in the annealed powder. The results suggest that FAST holds potential for rapid production of uniform cathode materials with low-cost nitrate precursors and minimal energy input. 相似文献
3.
Jouni Puranen Mikko Pihlatie Juha Lagerbom Giovanni Bolelli Jarmo Laakso Leo Hyvärinen Mikko Kylmälahti Olli Himanen Jari Kiviaho Luca Lusvarghi Petri Vuoristo 《International Journal of Hydrogen Energy》2014
Interconnects employed in solid oxide fuel cells require electrically conductive protective coatings such as those based on manganese cobalt oxide spinels in order to prevent evaporation of volatile Cr(VI)-compounds and to minimize high temperature corrosion. MnCo2−xFexO4 based (where x = 0.1 and 0.3) oxide spinel protective coatings were manufactured by the atmospheric plasma spraying process on Crofer 22 APU substrates. The coated substrates were oxidized at 700 °C in air for 1000 h and post-mortem analyses were conducted to study the performance of the thermal sprayed coatings. During the high temperature oxidation, a four-point on-line measurement technique was used for area specific resistance studies. The MnCo1.7Fe0.3O4 coating was tested together with the La0.85Sr0.15Mn1.1O3-spacer. 相似文献
4.
Thermal decomposition of (NH4)2SO4 in presence of Mn3O4 总被引:1,自引:0,他引:1
Liqun Mao Ali T-RaissiCunping Huang Nazim Z. Muradov 《International Journal of Hydrogen Energy》2011,36(10):5822-5827
The main objective of this work is to develop a hybrid water-splitting cycle that employs the photon component of sunlight for production of H2 and its thermal (i.e. IR) component for generating oxygen. In this paper, (NH4)2SO4 thermal decomposition in the presence of Mn3O4, as an oxygen evolving step, was systematically investigated using thermogravimetric/differential thermal analyses (TG/DTA), temperature programmed desorption (TPD) coupled with a mass spectrometer (MS), X-ray Diffraction (XRD), and X-ray Photoelectron Spectroscopy (XPS) techniques. Furthermore, thermolysis of ammonium sulfate, (NH4)2SO4, in the presence of Mn3O4 was also investigated by conducting flow reactor experiments. The experimental results obtained indicate that at 200-450 °C, (NH4)2SO4 decomposes forming NH3 and H2O and sulfur trioxide that in the presence of manganese oxide react to form manganese sulfate, MnSO4. At still higher temperatures (800∼900 °C), MnSO4 further decomposed forming SO2 and O2. 相似文献
5.
Beom-Kyeong Park Jong-Won Lee Seung-Bok Lee Tak-Hyoung Lim Seok-Joo Park Chong-Ook Park Rak-Hyun Song 《International Journal of Hydrogen Energy》2013
An interconnect in solid oxide fuel cells electrically connects unit cells and separates fuel from oxidant in the adjoining cells. Metallic interconnects are usually coated with conductive oxides to improve their surface stability and to mitigate chromium poisoning of a cathode. In this study, Mn1.5Co1.5O4 (MCO) spinel oxides doped with Cu and Ni are synthesized and applied as protective coatings on a metallic interconnect (Crofer 22 APU). Doping of Cu and Ni into MCO improves sintering characteristics as well as electrical conductivity and thermal expansion match with the Crofer interconnect. The dense layers of Cu- and Ni-doped MCOs are fabricated on the interconnects by a slurry coating process and subsequent heat-treatment. The coated interconnects exhibit area-specific resistances as low as 13.9–17.6 mΩ cm2 at 800 °C. The Cu-doped MCO coating acts as an effective barrier to evaporation and migration of Cr-containing species from the interconnect, thereby reducing Cr poisoning of a cathode. 相似文献
6.
The Ni-rich precursor powders with spherical shape and filled morphologies were prepared by spray pyrolysis from the spray solution with citric acid, ethylene glycol and a drying control chemical additive. The precursor powders with controlled morphologies formed the LiNi0.8Co0.15Mn0.05O2 cathode powders with spherical shape and fine size by solid-state reaction with lithium hydroxide. However, the cathode powders prepared from the spray solution without additives had irregular morphologies and were large in size. The precursor powders with hollow and porous morphologies formed cathode powders with irregular and aggregated morphologies. The composition ratios of the nickel, cobalt and manganese components were maintained in the as-prepared, precursor and cathode powders. The initial discharge capacity of the LiNi0.8Co0.15Mn0.05O2 cathode powders with spherical shape and fine size tested at a temperature of 55 °C under a constant current density of 0.5 C was 215 mAh g−1. The discharge capacity of the LiNi0.8Co0.15Mn0.05O2 cathode powders decreased to 81% of the initial value after 30 cycles. 相似文献
7.
Sang Bu Ha Pyeong-Seok Cho Yoon Ho Cho Dokyol Lee Jong-Heun Lee 《Journal of power sources》2010,195(1):124-129
A range of La0.75Sr0.25Cr0.5Mn0.5O3−δ (LSCM) powders is prepared by the carbonate coprecipitation method for use as anodes in solid oxide fuel cells. The supersaturation ratio (R = [(NH4)2CO3]/([La3+] + [Sr2+] + [Cr3+] + [Mn2+])) during the coprecipitation determines the relative compositions of La, Sr, Cr, and Mn. The composition of the precursor approaches the stoichiometric one at the supersaturation range of 4 ≤ R ≤ 12.5, whereas Sr and Mn components are deficient at R < 4 and excessive at R = 25. The fine and phase-pure LSCM powders are prepared by heat treatment at very low temperature (1000 °C) at R = 7.5 and 12.5. By contrast, the solid-state reaction requires a higher heat-treatment temperature (1400 °C). The catalytic activity of the LSCM electrodes is enhanced by using carbonate-derived powders to manipulate the electrode microstructures. 相似文献
8.
Hidesato Saruwatari Tadaomi IshikawaYoshiyuki Korechika Naoto KitamuraNorio Takami Yasushi Idemoto 《Journal of power sources》2011,196(23):10126-10132
The electrochemical properties and crystal structure of LiMn1.5Ni0.5O4 treated with supersonic waves in an aqueous Ni-containing solution were investigated by performing charge-discharge tests, inductively coupled plasma (ICP) analysis, scanning electron microscopy (SEM), iodometry, X-ray diffraction (XRD), powder neutron diffraction and synchrotron powder XRD. The charge-discharge curve of LiMn1.5Ni0.5O4 versus Li/Li+ has plateaus at 4.1 and 4.7 V. The 4.1 V versus Li/Li+ plateau due to the oxidation of Mn3+/4+ was reduced by the supersonic treatment. During the charge-discharge cycling test at 25 °C, the supersonic treatment increased the discharge capacity of the 50th cycle. Rietveld analysis of the neutron diffraction patterns revealed that the Ni occupancy of the 4b site in LiMn1.5Mn0.5O4, which is mainly occupied by Ni, was increased by the supersonic treatment. This result suggests that Ni2+ is partially substituted for Mn3+/4+ during the supersonic treatment. 相似文献
9.
Solution combustion synthesized (SCS) cobalt oxide (Co3O4) powder has been studied as a catalyst precursor for the hydrolysis of sodium borohydride (NaBH4). Synthesis is completed in less than two minutes and results indicate SCS is capable of reproducibly synthesizing 98.5–99.5% pure Co3O4 nano-foam materials. SCS materials demonstrate an as-synthesized specific surface area of 24 m2 g−1, a crystallite size of 15.5 nm, and fine surface structures on the order of 4 nm. Despite having similar initial surface areas and sample purities, SCS-Co3O4 outperforms commercially available Co3O4 and elemental cobalt (Co) nano powders when used as a catalyst precursor for NaBH4 hydrolysis. Hydrogen generation rates (HGR) using 0.6 wt% NaBH4 in aqueous solution at 20 °C were observed to be 1.24 ± 0.2 L min−1 gcat−1 for SCS nano-foam Co3O4 compared to 0.90 ± 0.09 and 0.43 ± 0.04 L min−1 gcat−1 for commercially available Co3O4 and Co, respectively. The high catalytic activity of SCS-Co3O4 is attributed to its nano-foam morphology and crystallinity. During the hydrolysis of NaBH4, the SCS-Co3O4 converts in-situ to an amorphous active catalyst with a specific surface area of 92 m2 g−1 and exhibits a honeycomb type morphology. 相似文献
10.
《International Journal of Hydrogen Energy》2020,45(29):14867-14879
The design of efficient electrocatalysts for oxygen evolution reaction (OER) is an essential task in developing sustainable water splitting technology for the production of hydrogen. In this work, manganese cobalt spinel oxides with a general formula of MnxCo3-xO4 (x = 0, 0.5, 1, 1.5, 2) were synthesised via a soft chemistry method. Non-equilibrium mixed powder compositions were produced, resulting in high electrocatalytic activity. The oxygen evolution reaction was evaluated in an alkaline medium (1 M KOH). It was shown that the addition of Mn (up to x ≤ 1) to the cubic Co3O4 phase results in an increase of the electrocatalytic performance. The lowest overpotential was obtained for the composition designated as MnCo2O4, which exhibited a dual-phase structure (∼30% Co3O4 + 70% Mn1.4Co1.6O4): the benchmark current density of 10 mA cm−2 was achieved at the relatively low overpotential of 327 mV. The corresponding Tafel slope was determined to be ∼79 mV dec−1. Stabilities of the electrodes were tested for 25 h, showing degradation of the MnCo2O4 powder, but no degradation, or even a slight activation for other spinels. 相似文献
11.
Co-rich and crack-free Mn–Co oxide coatings were deposited on AISI 430 substrates by anodic electrodeposition from aqueous solutions. The as-deposited Mn–Co oxide coatings, with nano-scale fibrous morphology and a metastable rock salt-type structure, evolved into a (Cr,Mn,Co)3O4 spinel layer due to the outward diffusion of Cr from the AISI 430 substrates when pretreated in air. The Mn–Co oxide coatings were reduced into metallic Co and Mn3O4 phases when annealed in a reducing atmosphere of 5% H2–95% N2. In contrast to the degraded oxidation resistance and electrical properties observed for the air-pretreated Mn–Co oxide coated samples, the H2-pretreated Mn–Co oxide coatings not only acted as a protective barrier to reduce the Cr outward diffusion, but also improved the electrical performance of the steel interconnects. The improvement in electronic conductivity can be ascribed to the higher electronic conductivity of the Co-rich spinel layer and better adhesion of the scale to the steel substrate, thereby eliminating scale spallation. 相似文献
12.
The compatibility between dimethyl methylphosphonate (DMMP)-based electrolyte of 1 M LiPF6/EC + DMC + DMMP (1:1:2 wt.) and spinel materials Li4Ti5O12 and LiNi0.5Mn1.5O4 was reviewed, respectively. The cell performance and impedance of 3-V LiNi0.5Mn1.5O4/Li4Ti5O12 lithium-ion cell with the DMMP-based nonflammable electrolyte was compared with the baseline electrolyte of 1 M LiPF6/EC + DMC (1:1 wt.). The nonflammable DMMP-based electrolyte exhibited good compatibility with spinel Li4Ti5O12 anode and high-voltage LiNi0.5Mn1.5O4 cathode, and acceptable cycling performance in the LiNi0.5Mn1.5O4/Li4Ti5O12 full-cell, except for the higher impedance than that in the baseline electrolyte. All of the results disclosed that the 3 V LiNi0.5Mn1.5O4/Li4Ti5O12 lithium-ion battery was a promising choice for the nonflammable DMMP-based electrolyte. 相似文献
13.
《International Journal of Hydrogen Energy》2019,44(8):4317-4331
Manganese, cobalt and nickel metal powders are mixed with 10 wt% oxides: La0·6Sr0·4CoO3, La0·6Sr0·4Co0·2Fe0·8O3, La0·8Sr0·2MnO3 and MnCo2O4, to form ten compositions. Powder mixtures are studied as cathode contact materials in solid oxide fuel cell stacks. Electrical resistance is measured on samples of powder pellets and steel/powder/steel assemblies at 800 °C for over 10000 h. Microstructures are examined after measurements. For the powder pellets, Mn-Co (mole ratio 1:2) and Ni-Co (mole ratio 1:2) with MnCo2O4 exhibit minimum resistivity in the Mn-Co and Ni-Co series respectively. For the steel/powder/steel assemblies, Mn-Co (mole ratio 1:1) with La0·6Sr0·4CoO3 and Ni-Co (mole ratio 1:2) with La0·8Sr0·2MnO3 show close low values. Oxide scales grown on steel surfaces which contact powders with lanthanum-based perovskites are irregular and thinner. Other powders result in more regular and thicker oxide layers. The two forms of oxide structures are in accordance with the two trends of electrical resistance change observed in the assemblies. The addition of lanthanum-based perovskites reveals phenomenal effects on reducing the resistivity of powder mixtures and suppressing the growth of steel oxide scales. 相似文献
14.
The spinel LiNi0.5Mn1.5O4 has been surface modified separately with 1.0 wt.% ZrO2 and ZrP2O7 for the purpose of improving its cycle performance as a cathode in a 5-V lithium-ion cell. Although the modifications did not change the crystallographic structure of the surface-modified samples, they exhibited better cyclability at elevated temperature (55 °C) compared with pristine LiNi0.5Mn1.5O4. The material that was surface modified with ZrO2 gave the best cycling performance, only 4% loss of capacity after 150 cycles at 55 °C. Electrochemical impedance spectroscopy demonstrated that the improved performance of the ZrO2-surface-modified LiNi0.5Mn1.5O4 is due to a small decrease in the charge transfer resistance, indicating limited surface reactivity during cycling. Differential scanning calorimetry showed that the ZrO2-modified LiNi0.5Mn1.5O4 exhibits lower heat generation and higher onset reaction temperature compared to the pristine material. The excellent cycling and safety performance of the ZrO2-modified LiNi0.5Mn1.5O4 electrode was found to be due to the protective effect of homogeneous ZrO2 nano-particles that form on the LiNi0.5Mn1.5O4, as shown by transmission electron microscopy. 相似文献
15.
In this paper we report the solution combustion synthesis of cobalt oxide nanofoam from solutions of cobalt nitrate and glycine and subsequent use as an effective catalyst precursor for NaBH4 hydrolysis. The catalytic activity results show that the hydrogen generation rate (HGR) at room temperature was much higher for the solution combustion synthesized material than for commercial Co3O4 nanopowder, though their specific surface areas were comparable (∼26–32 m2/g). Using a 0.6 wt.% aqueous solution of NaBH4 at 20 °C and a 5 wt.% catalyst precursor loading, a HGR of 1.93 L min−1 gcat−1 was achieved for solution combustion synthesized Co3O4. In contrast, at the same conditions, for commercial Co3O4 and elemental Co powders HGRs of 0.98 and 0.49 L min−1 gcat−1 were achieved respectively. This type of synthesis is amenable to many complex metal oxide catalysts as well, such as LiCoO2, which have also been shown to be good catalyst precursors for hydrolysis of NaBH4. 相似文献
16.
Subramanian Keerthana Rathinam Yuvakkumar Ganesan Ravi Balasubramaniam Saravanakumar Mehboobali Pannipara Abdullah G. Al-Sehemi Dhayalan Velauthapillai 《International Journal of Hydrogen Energy》2021,46(33):17060-17070
In this study, nickel cobalt oxide (NiCo2O4) microspheres were prepared by using facile hydrothermal route. The structural confirmation of bimetal oxide formation was acquired by X-ray powder diffraction and Raman studies. The formation of microspheres combined via irregular nanosheets was confirmed by scanning electron microscopy. Highly oriented NiCo2O4 microspheres yielded a high current density (258 mA/g) at 10 mV/s and low overpotential (224 V). The highly active electrode showed efficient electron transportation towards oxygen evolution reaction. Long-term stability over 16 h was achieved by the fabricated high-performance NiCo2O4 electrode. It is recommended that NiCo2O4 microspheres obtained from 3:1 stoichiometry ratio of Ni and Co would lead to new electrocatalysts that give best performance than expensive catalysts used currently in the water oxidation process. 相似文献
17.
《Journal of power sources》2006,161(1):19-26
The effect of nickel and sulfur substitution for manganese and oxygen on the structure and electrochemical properties of the LiNi0.5Mn1.5O4−xSx is examined. The LiNi0.5Mn1.5O4−xSx (x = 0 and 0.05) compounds are successfully synthesized at 500 and 800 °C by co-precipitation using the metal carbonate (Ni0.5Mn1.5)CO3 as a precursor. The resulting powder with sulfur doping exhibits different morphology from a Ni-only doped spinel in terms of particle size and surface texture. The LiNi0.5Mn1.5O4−xSx (x = 0 and 0.05) powders are characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and galvanostatic charge–discharge cycling. The nickel- and sulfur-doped spinel displays excellent capacity retention and rate capability in the 3-V region, compared with Ni-only doped spinel material. 相似文献
18.
Javier Marugán Juan A. Botas Mariana Martín Raúl Molina Carolina Herradón 《International Journal of Hydrogen Energy》2012
In this work, a complete thermodynamic study of the first step of the Mn2O3/MnO thermochemical cycle for solar hydrogen production has been performed. The thermal reduction of Mn2O3 takes place through a sequential mechanism of two reaction steps. The first step (reduction of Mn2O3 to Mn3O4) takes place at teomperatures above 700 °C, whereas the second reaction step (reduction of Mn3O4 to MnO) requires temperatures above 1350 °C to achieve satisfactory reaction rates and conversions. Equilibrium can be displaced to lower temperatures by increasing the inert gas/Mn2O3 ratio or decreasing the pressure. The thermodynamic calculations have been validated by thermogravimetric experiments carried out in a high temperature tubular furnace. Experimental results corroborate the theoretical predictions although a dramatically influence of chemical kinetics and diffusion process has been also demonstrated, displacing the reactions to higher temperatures than those predicted by thermodynamics. Finally, this work demonstrates that the first step of the manganese oxide thermochemical cycle for hydrogen production can be carried out with total conversion at temperatures compatible with solar energy concentration devices. The range of required temperatures is lower than those commonly reported in literature for the manganese oxide cycle obtained from theoretical and thermodynamic studies. 相似文献
19.
In this communication, a porous hierarchical nanostructure consisting of amorphous MnO2 (a-MnO2), Mn3O4 nanocrystals, and single-crystalline MnOOH nanowires is designed for the supercapacitor application, which is prepared by a simple two-step electrochemical deposition process. Because of the gradual co-transformation of Mn3O4 nanocrystals and a-MnO2 nanorods into an amorphous manganese oxide, the cycle stability of a-MnO2 is obviously enhanced by adding Mn3O4. This unique ternary oxide nanocomposite with 100-cycle CV activation exhibits excellent capacitive performances, i.e., excellent reversibility, high specific capacitances (470 F g−1 in CaCl2), high power property, and outstanding cycle stability. The highly porous microstructures of this composite before and after the 10,000-cycle CV test are examined by means of scanning electron microscopy (SEM) and transmission electron microscopy (TEM). 相似文献
20.
Sub-micro spinel LiNi0.5−xMn1.5+xO4 (x < 0.1) cathode materials powder was successfully synthesized by the ultrasonic-assisted co-precipitation (UACP) method. The structure and electrochemical performance of this as-prepared powder were characterized by powder XRD, SEM, XPS, CV and the galvanostatic charge–discharge test in detail. XRD shows that there is a small LiyNi1−yO impurity peak placed close to the (4 0 0) line of the spinel LiNi0.5−xMn1.5+xO4, and the powders are well crystallized. XPS exhibits that the Mn oxidation state is between +3 and +4, and Ni oxidation state is +2 in LiNi0.5−xMn1.5+xO4. SEM shows that the prepared powders (UACP) have the uniform and narrow size distribution which is less than 200 nm. Galvanostatic charge–discharge test indicates that the initial discharge capacities for the LiNi0.5−xMn1.5+xO4 (UACP) at C/3, 1C and 2C, are 130.2, 119.0 and 110.0 mAh g−1, respectively. After 100 cycles, their capacity retentions are 99.8%, 88.2%, and 73.5%, respectively. LiNi0.5−xMn1.5+xO4 (UACP) at C/3 discharge rate exhibits superior capacity retention upon cycling, and it also shows well high current discharge performance. CV curve implies that LiNi0.5−xMn1.5+xO4 (x < 0.1) spinel synthesized by ultrasonic-assisted co-precipitation method has both reversibility and cycle capability because of the ultrasonic-catalysis. 相似文献