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1.
Solid Oxide Electrolyzer Cells (SOECs) are promising energy devices for the production of syngas (H2/CO) by H2O and/or CO2 electrolysis. Here we developed a Cu–Ce0.9Gd0.1O2−δ/Ce0.8Gd0.2O2−δ/Ba0.5Sr0.5Co0.8Fe0.2O3−δ-Ce0.8Gd0.2O2−δ cell and performed H2O and CO2 electrolysis experiments in the intermediate temperature range (600°C–700 °C). As a baseline, the cell was first tested in fuel cell operation mode; the sample shows a maximum power density peak of 104 mW cm−2 at 700 °C under pure hydrogen and air. H2O electrolysis testing revealed a steady production of hydrogen with a Faraday's efficiency of 32% at 700 °C at an imposed current density of −78 mA cm−2. CO production was observed during CO2 electrolysis but higher cell voltages were required. A lower efficiency of about 4% was obtained at 700 °C at an imposed current density of −660 mA cm−2. These results confirm that syngas production is feasible by water and carbon dioxide electrolysis but further improvements from both the manufacturing and the electrocatalytic aspects are needed to reach higher yields and efficiencies.  相似文献   

2.
A 2D computational fluid dynamics (CFD) model was developed to study the performance of a planar solid oxide electrolyzer cell (SOEC) for hydrogen production. The governing equations for mass continuity, momentum conservation, energy conservation and species conservation were discretized with the finite volume method (FVM). The coupling of velocity and pressure was treated with the SIMPLEC (Semi-Implicit Method for Pressure Linked Equations – Consistent) algorithm. Simulations were performed to investigate the effects of operating/structural parameters on heat/mass transfer and the electric characteristics of a planar SOEC. It is found that the gas velocity at the cathode increases significantly along the main flow channel, as the increase in H2 molar fraction decreases the density and viscosity of the gas mixture at the cathode. It is also found that increasing the inlet gas velocity can enhance the SOEC performance. Another important finding is that the electrode porosity has small effect on SOEC performance. The results of this paper provide better understanding on the coupled heat/mass transfer and electrochemical reaction phenomena in an SOEC. The model developed can serve as a useful tool for SOEC design optimization.  相似文献   

3.
Biologically produced mixtures of H2 and CO2 (biohydrogen) from processes such as dark fermentation or photo-fermentation are versatile feedstocks which can potentially be utilised in solid oxide cell (SOC) devices. In this work, solid oxide electrolysis of biohydrogen has been investigated for the first time and is compared directly with fuel cell mode utilisation. The performance and fuel processing of SOCs utilising biohydrogen have been characterised in greater detail than has been achieved previously through the use of experiments which combine electrochemical techniques with quadrupole mass spectrometry (QMS). The effects of fuel variability on SOC overpotentials and outputs have been established and it is shown that cell performance is not significantly affected provided the fuel composition stays within 40–60 vol% H2. QMS measurements indicate H2O and CO production takes place in-situ via the reverse water-gas shift (RWGS) reaction. Electrical power production in fuel cell mode is predominantly through H2 oxidation, whilst CO is converted in the WGS reaction to regenerate CO2 but does not contribute to electrical power production. In electrolysis mode, CO is produced simultaneously through electrochemical CO2 reduction and the RWGS reaction; H2O is electrochemically reduced to regenerate H2.  相似文献   

4.
This paper describes results on the electrochemical reduction of carbon dioxide using the same device as the typical planar nickel-YSZ cermet electrode supported solid oxide fuel cells (H2-CO2, Ni-YSZ|YSZ|LSCF-GDC, LSCF, air). Operation in both the fuel cell and the electrolysis mode indicates that the electrodes could work reversibly for the charge transfer processes. An electrolysis current density of ≈1 A cm−2 is observed at 800 °C and 1.3 V for an inlet mixtures of 25% H2-75% CO2. Mass spectra measurement suggests that the nickel-YSZ cermet electrode is highly effective for reduction of CO2 to CO. Analysis of the gas transport in the porous electrode and the adsorption/desorption process over the nickel surface indicates that the cathodic reactions are probably dominated by the reduction of steam to hydrogen, whereas carbon monoxide is mainly produced via the reverse water gas shift reaction.  相似文献   

5.
The double perovskite Sr2CoMoO6−δ was investigated as a candidate anode for a solid oxide fuel cell (SOFC). Thermogravimetric analysis (TGA) and powder X-ray diffraction (XRD) showed that the cation array is retained to 800 °C in H2 atmosphere with the introduction of a limited concentration of oxide-ion vacancies. Stoichiometric Sr2CoMoO6 has an antiferromagnetic Néel temperature TN ≈ 37 K, but after reduction in H2 at 800 °C for 10 h, long-range magnetic order appears to set in above 300 K. In H2, the electronic conductivity increases sharply with temperature in the interval 400 °C < T < 500 °C due to the onset of a loss of oxygen to make Sr2CoMoO6−δ a good mixed oxide-ion/electronic conductor (MIEC). With a 300-μm-thick La0.8Sr0.12Ga0.83Mg0.17O2.815 (LSGM) as oxide-ion electrolyte and SrCo0.8Fe0.2O3−δ as the cathode, the Sr2CoMoO6−δ anode gave a maximum power density of 1017 mW cm−2 in H2 and 634 mW cm−2 in wet CH4. A degradation of power in CH4 was observed, which could be attributed to coke build up observed by energy dispersive spectroscopy (EDS).  相似文献   

6.
A model is presented that describes the main physical phenomena affecting in the performance of a Solid-Oxide Fuel Cell (SOFC). The implementation of the model uses an in-house algorithm in a computational fluid-dynamics (CFD) framework that may be used to optimize the SOFC operational parameters. The physical phenomena considered in the model are: (i) mass conservation: multicomponent and multimodal mass transfer in gas channels and electrodes (convection, ordinary diffusion, Knudsen diffusion); (ii) momentum conservation in the gas channels and electrodes; (iii) energy conservation: coupled heat transfer across the whole cell (gas channels, electrodes and electrolyte); (iv) electrochemistry: half-reactions are considered to take place at the electrode-electrolyte interfaces, and activation losses are computed using the general version of the Butler-Volmer equation. The main features of this CFD tool are: (i) it allows the prediction of the characteristic (I-V) curve of an H2-fed cell; (ii) it is suitable for both tubular and planar cells; (iii) it has been implemented using OpenFOAM-1.5-dev, an open-source CFD-platform based on the Finite Volume Method.The numerical results are validated with published experimental I-V curves for a hydrogen-fed anode-supported micro-tubular SOFC, and a numerical analysis of the influence of different operation conditions on the temperature distribution is performed to procure a better understanding of the heat management of the cell.  相似文献   

7.
The effective binary diffusivity of H2 and H2O in a Ni and yittria-stabilized zirconia (YSZ) anode of the solid oxide fuel cells (SOFCs) was measured between 650 and 800 °C using an electrochemical cell consisting of an oxygen pump, an oxygen sensor, and a porous SOFC anode pellet. The effective binary diffusivity was obtained from the relationship between the current density across the oxygen pump, and the H2 partial pressure gradient across the anode sample measured using the oxygen sensor. The anode limiting current density and concentration polarization were estimated using the experimental results.  相似文献   

8.
This study investigated the effect of H2S concentration (5, 10 and 50 ppm) on the degradation and performance of Ni-YSZ anode supported solid oxide fuel cells. When supplied with hydrogen fuel containing H2S, the cell voltage dropped rapidly, and with increasing H2S concentration, voltage drop % increased (due to higher sulfur coverage on the Ni surface) and saturated more rapidly. A high concentration (50 ppm) of H2S led to an additional, slow rate voltage loss. In all cases, cell performance did not completely recover even after being supplied with H2S-free hydrogen fuel, because of the incomplete desorption of sulfur from the Ni surface. After the performance tests, nickel sulfides were detected on the Ni surface by Raman spectra, which were produced by the reaction of the remaining adsorbed sulfur with Ni during the cooling process. This indicates that the formation of nickel sulfides was not responsible for the secondary voltage drop. SEM/EDS analyses combined with FIB revealed that the reason for the additional 2nd drop was Ni oxidation; at a high sulfur coverage ratio (50 ppm), the outer layer of the Ni particle was oxidized by oxygen ions transported from the electrolyte. This indicates that H2S concentration as well as current density is a critical factor for Ni oxidation, and gives rise to the second voltage drop (irreversible cell degradation). The present work showed that the degradation behavior and phenomenon can differ significantly depending on the concentration of H2S, i.e., permanent changes may or may not occur on the anode (such as Ni oxidation) depending upon H2S concentration.  相似文献   

9.
This paper presents a novel system for production of pure oxygen based on the integration of a solid oxide fuel cell (SOFC) and a solid oxide electrolyzer (SOEC). In the proposed arrangement, the SOFC provides electricity, heat and H2O in vapour phase to the SOEC which carries out the inverse reactions of the SOFC, that is the separation of H2O into H2 (used as a fuel for the SOFC) and O2 (representing the yield of the system). Simulations carried out in different operating conditions show that when the integrated SOFC–SOEC device runs at low current densities (less than 1000 A m−2), pure oxygen can be generated with an electric consumption comparable to mid-size cryogenic air separation units, and significantly lower than small scale systems based on the PSA technology.  相似文献   

10.
Thermochemical gasification of biomass through the supercritical water gasification (SCWG) has high gasification efficiency at lower temperatures and can deal directly with wet biomass without drying. Besides, solid oxide fuel cells (SOFCs) appear to be an important technology in the future as they can operate at a high efficiency. Therefore, the combination of biomass gasification through supercritical water with SOFC represents one of the most potential applications for highly efficient utilization of biomass.  相似文献   

11.
Fabricating a large-area unit cell is very important for the development of solid oxide fuel cell (SOFC) stack. In this study, details of sintering process of half cell with NiO-yttria stabilized zirconia (YSZ) anode-supported YSZ thin electrolyte film fabricated by co-tape casting have been discussed. The results demonstrates that the shrinkages and shrinking rates mismatches between the electrolyte and the anode can be controlled by the organic additive content in the anode slurry composition and heating rate. Low heating rate suppresses the cracks formation in the electrolyte films. A warp-free unit cell with size of 100 × 100 mm2 and dense electrolyte has been successfully fabricated. A power of 22.2 W, with a power density of 0.27 W cm−2 has been achieved at 0.7 V and 750 °C in O2/humidified H2 atmosphere. The area specific resistance of the cell is 1.20 Ω cm2 at 0.7 V and 750 °C.  相似文献   

12.
The apparent densities, coefficients of thermal expansion (CTE), and softening points of the BaO-Al2O3-SiO2-B2O3 glasses prepared in this study range from 2.61 to 3.92 g/cm3, 4.92 to 10.98 ppm/°C, and 656 to 854 °C, respectively, depending on the glass composition. The softening point decreases with increasing BaO or B2O3 content in the glass. The feasibility of using MgO, KAlSi2O6, and KAlSiO4 to tune the CTE of BaO-Al2O3-SiO2-B2O3 glass is investigated. Composites containing MgO additive show little change in CTE at high temperature and report a high structural stability with the change in time. Wetting angle of the glass on the YSZ substrate depends to a great extent on the soaking temperature and the BaO content in the glass. Composites of selected BaO-Al2O3-SiO2-B2O3 glasses and MgO additive on the YSZ substrate are evaluated for use as sealing material of solid oxide fuel cells (SOFCs). Results indicate that leakage rates for the composites of L06-20 vol% MgO, L08-30 vol% MgO, and L09-40 vol% MgO are lower than the detectable limit in this study.  相似文献   

13.
A two-cell planar stack in the Jülich F-design with solid oxide cells has been built and the reversible operation between fuel cell and electrolysis modes has been demonstrated. The cells were anode supported cells (ASC) with yttria-stabilized zirconia (YSZ) electrolytes, Ni/YSZ hydrogen electrodes and perovskite oxygen electrodes with lanthanum strontium cobalt ferrite (LSCF). This paper summarizes and discusses the preliminary experimental results on the long-term aging tests of the reversible solid oxide planar short stack for fuel cell operation (4000 h) at a current density of 0.5 A cm−2 which shows a degradation of 0.6% per 1000 h and for steam electrolysis operation (3450 h) and co-electrolysis operation of CO2 and H2O (640 h) under different current densities from −0.3 to −0.875 A cm−2 which show different degradation rates depending on current density and on steam or co-electrolysis.  相似文献   

14.
La2O3-Al2O3-B2O3-SiO2 glasses free of alkaline earth metals were prepared in this study for SOFC applications to relieve the poison caused by BaCrO4 or SrCrO4 formation. The apparent densities, coefficients of thermal expansion (CTE), and softening points of the La2O3-Al2O3-SiO2-B2O3 glasses prepared in this study ranged respectively from 3.24 to 4.54 g/cm3, 4.1 to 8.1 ppm/°C, and 912 to 937 °C, depending on the glass composition. The CTE value dropped with the rise in SiO2 content and escalated with increase in La2O3 content. Crystallization of La9.51(SiO1.0404)6O2 and La4.67(SiO4)3O was observed in part of the glasses after soaking at 800 °C. Two CTE modifiers, MgO and SDC, effectively increased the CTE of La2O3-Al2O3-SiO2-B2O3 glasses. The composites of selected La2O3-Al2O3-B2O3-SiO2 glasses and SDC additive on the YSZ substrate were evaluated for use as sealing materials of solid oxide fuel cells (SOFCs). Results indicated that the leakage rates for the composites of A07 glass and 60-70 vol% SDC on the YSZ plate read less than 0.02 (sccm/cm)(kg/cm2) per min at 800 °C. This property seems highly promising for ensuring long-term stability of the sealing materials for SOFC applications.  相似文献   

15.
High-temperature solid oxide electrolyzer cell (SOEC) has great potential for efficient and economical production of hydrogen fuel. In this paper, the state-of-the-art SOEC technologies are reviewed. The developments of the important steam electrolyzer components, such as the ionic conducting electrolyte and the electrodes, are summarized and discussed. YSZ and LSGM are promising electrolyte materials for SOEC working at high and intermediate temperatures, respectively. When co-doping or a blocking layer is applied, SDC or GDC are possible electrolyte materials for intermediate-temperature SOEC. Ni–YSZ remains to be the optimal cathode material. Although LSM–YSZ is widely used as SOEC anode, other materials, such as LSF–YSZ, may be better choices and need to be further studied. Considering the cell configuration, planar SOECs are preferred due to their better manufacturability and better electrochemical performance than tubular cells. Anode depolarization is an effective method to reduce the electrical energy consumption of SOEC hydrogen production. Although some electrochemical models and fluid flow models are available, the present literature is lacking detailed modeling analyses of the coupled heat/mass transfer and electrochemical reaction phenomena of the SOEC. Mathematical modeling studies of SOEC with novel structures and anode depolarization processes will be fruitful for the development of SOEC. More works, both experimental and theoretical, are needed to further develop SOEC technology to produce hydrogen more economically and efficiently for the coming hydrogen economy.  相似文献   

16.
Lanthanum strontium vanadate (LSV) was used as the cathode of a solid oxide electrolysis cell (SOEC) containing a yttria-stabilized zirconia (YSZ) electrolyte for the coelectrolysis of steam and CO2. Pd and CeO2 were added to the composite cathode, and the electrolysis mechanism in the coelectrolysis mode changed according to the type of catalyst in the LSV/YSZ composite cathode. The effect of steam on the coelectrolysis performance was investigated by varying the steam vapor pressure. The electrolysis performance under dry CO2 without steam degraded with time under electrochemical reduction conditions owing to the deactivation of catalysts.  相似文献   

17.
The Ca(V0.5Mo0.5)O3 perovskite has been prepared in order to study its potential use as anode in SOFC. The crystal structure has been refined, by neutron powder diffraction, in the orthorhombic Pbnm space group (no. 62). The electrical conductivity values were over 525 S cm−1 in the studied temperature range (25-800 °C). The sample is stable under reducing working conditions (H2/N2 10:90, 25-900 °C). This orthorhombic phase transforms at 500 °C in air to the tetragonal I41/a scheelite phase. This transition is reversible and, due to the fact that the thermal expansion coefficients of both, the reduced and oxidized phases, are very similar and match well with those of the other cell components ((10-13) × 10−6 K−1) this materials are presented as excellent candidates as anodes in SOFCs.  相似文献   

18.
This paper uses finite element method to study the effect of Al2O3 film on thermal stresses in the bonded compliant seal (BCS) design of a planar solid oxide fuel cell. The effects of Al2O3 thickness, operating temperature, window frame thickness, foil thickness and cell length on thermal stresses have been discussed. The results show that compressive stresses are generated in Al2O3 film. A bowing deformation is generated due to the BCS design, which can trap and relax some thermal stresses. With Al2O3 thickness increase, compressive stresses in Al2O3 film and foil are decreased slightly, while tensile stresses in BNi2 and frame are increased. With operating temperature increase, compressive stress in Al2O3 is increased greatly, while the stresses in foil, BNi2 and frame are increased slightly. The bowing deformation is increased with operating temperature increase. The window frame thickness has little effect on thermal stresses and bowing deformation. With sealing foil thickness increase, thermal stresses and bowing deformation are increased. The cell length has little effect on thermal stresses, but reducing the cell length can decrease the bowing deformation.  相似文献   

19.
Sulphur-containing impurities can have a damaging impact on nickel-based SOFC anode performance even at sub-ppm concentrations, but the electrochemical mechanism of this interaction is not fully understood. In this work, three-electrode cells of Ni-Ce0.9Gd0.1O1.95/YSZ/(La0.8Sr0.2)MnO3−x have been used to obtain new electrochemical data on the sulphur poisoning behaviour of Ni-based SOFC anodes operating at different current densities in the temperature range 700-750 °C. The three-electrode arrangement enabled direct measurement of anode overpotential, with concurrent impedance measurement to provide detail into the electrochemical processes occurring at the anode during sulphur poisoning.The initial, stepwise degradation on exposure to 0.5 ppm H2S caused an increase in anode polarization resistance, which was almost entirely recoverable on removal of H2S. Operation at higher current density was found to result in a smaller increase in anode polarization resistance. It is proposed that this initial poisoning behaviour is caused by adsorbed sulphur inhibiting surface diffusion of H atoms to active sites.Exposure to 1 ppm and 3 ppm levels of H2S led to an observed secondary degradation which was also recoverable on removal of sulphur. This degradation was caused by an increased ohmic resistance, and was more severe at higher temperatures. The authors discuss possible explanations for this behaviour.  相似文献   

20.
The segmented-in-series solid oxide fuel cell comprising fuel channel, anode, cathode and electrolyte layers has been evaluated by developing a two-dimensional model, in which the equations have been solved numerically through finite element methods. The results indicate that the voltage of each membrane electrode assembly (MEA) exhibits a parabola-like curve and is higher than the appointed voltage of unit cell (0.7 V). From fuel inlet to outlet, the voltage of each MEA deceases due to the decreasing local H2 concentration. When both the interconnector and electrolyte gap lengths are fixed, the cell module with 5 mm long anode gives the maximal power density for the SS-SOFC. Higher power densities can be achieved through increasing the cathode thickness.  相似文献   

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