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Flexible power sources including fuel cells and batteries are the key to realizing flexible electronic devices with pronounced foldability. To understand the bending effects in these devices, theoretical analysis on three-dimensional (3-D) lattice bending is necessary. In this report, we derive a 3-D analytical model to analyze the effects of electrolyte crystal bending on ionic conductivity in flexible solid-state batteries/fuel cells. By employing solid oxide fuel cells as a materials' platform, the intrinsic parameters of bent electrolyte materials, including lattice constant, Young's modulus, and Poisson ratio, are evaluated. Our work facilitates the rational design of highly efficient flexible electrolytes for high-performance flexible device applications. [ABSTRACT FROM AUTHOR]

Abstract A modern optimization algorithm is used for maximizing the performance of solid oxide fuel cell. At first, the cell is modeled using Artificial Neural Networks based on the experimental data sets. Then, a robust, simple, and quick optimization algorithm named radial movement optimizer is used for determining the optimal operating parameters of the cell. The cell parameters used in the optimization process are anode support layer thickness, anode porosity, electrolyte thickness, and cathode interlayer thickness. The optimization obtained results are compared with the previous optimized experimental results and those obtained using genetic algorithm. Two sets of the parameters' constraints are considered during the optimization process. In the first set, the resulting optimal cell parameters are 0.5 mm, 76%, 20 μm, and 62.26 μm for anode thickness, anode porosity, electrolyte thickness, and cathode thickness respectively. Under this condition, the cell maximum power density is 1.8 W/cm2, 2.25 W/cm2 and 2.72 W/cm2 for experimentally, genetic algorithm and the proposed strategy, respectively. This implies that using the proposed method increases the power density by 33.8% and 17.28% over the experimental and genetic, respectively. In the second set, the proposed optimizer increases the maximum power by 28.85% compared with genetic optimizer. Highlights • SOFC is modeled using Artificial Neural Networks (ANN) based on experimental data sets. • Radial movement optimizer (RMO) is used for determining the optimal operating parameters of the SOFC. • The optimized parameters are ASL thickness and porosity, electrolyte thickness, and cathode interlayer thickness. • A 33.8% and 17.28% increase in power density attained compared to experimental and genetic optimization. [ABSTRACT FROM AUTHOR]

Grain boundary conductivity of samarium doped ceria electrolyte (SDC) depends on the space charge potential and oxygen vacancy concentration existing at the grain boundary region. Here, we report the effect of co-doping 1 mol% divalent alkaline earth metals in samarium doped ceria (Ce 0.78 Sm 0.2 A 0.01 O 1.89 , [ASDC], A = Mg, Ca, Sr, Ba) on the grain boundary conductivity. The increase (Ca2+, Sr2+, Ba2+) or decrease (Mg2+) in lattice parameter in comparison to SDC (0.5445 nm) depends on the ionic radii of the co-dopant. The oxygen vacancy concentration of ASDC system, quantified from the Raman spectra, increased from 2.98 × 1021 cm−3 (SDC) to 3.18 × 1021 cm−3. The samples sintered at 1400 °C for 5 h, resulted in a dense electrolyte with a relative density of 98–99%. Calcium co-doped SDC (CSDC) showed the highest conductivity of 2.04 × 10−3 S/cm at 700 °C with activation energy of 0.90 eV. The oxygen vacancy profile at the space charge layer was found to be higher for CSDC while the potential reduced from 0.24 V (SDC) to 0.18 V. The observed lower space charge potential in co-doped SDC, contributed to the enhancement in oxygen vacancy concentration at the space charge layer and increased the grain boundary conductivity. Thus the present study highlights the correlation of space charge potential, oxygen vacancy concentration to grain boundary conductivity and provide a profound insights on the grain boundary understandings for improving the performance of the electrolyte for solid oxide fuel cell application. • Alkaline earth metal co-doped SDC, prepared by citrate nitrate combustion method. • Solid solubility varied with the ionic radii of the co-dopants. • Grain boundary was scavenged by reducing the space charge potential of SDC. • Lowering the potential enhanced oxygen vacancy concentration at grain boundary. [ABSTRACT FROM AUTHOR]

• Solid oxide fuel cell electrode microstructure is modeled from fabrication to operation. • 1D lattice Boltzmann model is used for fast evaluation of electrode overpotential. • Time-evolutions of the microstructure parameters and overpotential are studied. • Correlations between microstructures and overpotentials are studied based on 13,860 distinct microstructures. • A response surface model is established for fast prediction of overpotential from microstructural parameters. In this study, a numerical framework which jointly uses discrete element method, kinetic Monte Carlo method and lattice Boltzmann method is proposed to predict the electrochemical performance of solid oxide fuel cell cathode from raw powder. A total of 770 La 0.6 Sr 0.4 Co 0.2 Fe 0.8 O 3−δ (LSCF) cathodes with different microstructures are numerically synthesized using various particle size, size distribution, pore former content and sintering time. Best performance is found at a porosity of approximately 0.40. The cathode performance degrades tremendously at about a critical porosity of 0.10–0.25 because the pores become disconnected. The critical porosity is found to have a positive linear dependency on the mean pore size. Cathodes that have smaller mean pore size may still operate functionally at a low porosity of 0.10. A response surface model (RSM) is proposed to predict the overpotential from microstructural parameters. The RSM is also found to be valid for real cathode microstructures and can be served as an off-line assessment tool for the cathode performance. [ABSTRACT FROM AUTHOR]

In this study, we evaluate lanthanum strontium cobalt ferrite (LSCF) surface-coated with lanthanum nickelate (LNO) fabricated by aerosol-assisted chemical vapor deposition (AACVD) for application in solid oxide fuel cells (SOFCs). The AACVD method successfully produces LNO in the desired composition and crystal structure. The deposited LNO is confirmed to form a dense and uniform layer along the nano-porous LSCF support. The LSCF with an optimal amount of LNO surface clearly enhances the SOFC performance, showing a power increase of approximately 60% at 600 °C in our experiment. This enhancement results from the reduction of both ohmic and polarization resistance, presumably due to improved cathodic surface kinetics and current collection. This AACVD LNO-treatment is also confirmed to be effective in improving long-term stability, significantly suppressing the power decrease observed in an untreated sample. [ABSTRACT FROM AUTHOR]

Summary: Reversible solid oxide fuel cells (rSOFCs) may be applied to store and generate electrical energy in a reversible mode. This technique is promising to balance the conflict between intermittent power supply and demand in a sustainable way. One of the limitations of the development of rSOFCs is the high cost of storage and usage of pure H2, which may be solved by employing syngas as the fuel. The performance of rSOFCs depends on the development of bifunctional materials, cell design, and operation optimization, which are often investigated and predicted by the cost‐effective approach of mathematical modeling. However, the modeling of dual‐mode rSOFCs involving co‐redox reactions with syngas is not well developed. In this study, a two‐dimensional (2D) single‐channel model of an rSOFC is developed. The novelty of this model is that the multiphysics transport processes are fully coupled and solved with the reversible water‐gas shift reaction with syngas and the electrochemical reactions. The effects of the operating conditions and design parameters (eg, electrode thickness) are considered, with the aim of providing guidelines to optimize the design and operation of reversible cells. It is concluded that the thickness of the electrode has a larger impact on the water‐gas shift reaction than on the electrochemical reaction in both the gas diffusion and reaction regions. The C/H element ratio of syngas has a negative correlation with power output, but the distributions of current and gas species may be improved in both modes. A higher operating temperature improves the performance in both modes but has a more substantial effect in the electrolysis mode. The specific design and operating schemes favored in different modes should be balanced in the reversible mode. [ABSTRACT FROM AUTHOR]

Fuel composition fluctuation could result in operation performance degradation caused by a potential failure of component or system. Therefore, this work elaborated the safe characteristic and load performance of an intermediate-temperature solid oxide fuel cell (IT-SOFC) and gas turbine (GT) hybrid system using gasified biomass gas when the composition fluctuates. The malfunction restrictions of components (such as fuel cell thermal crack, compressor surge, reformer carbon deposition) were considered in this research. Results show that the hybrid system has a high efficiency 60.78% at the design point using gasified wood chip gas, which is a useful reference for small distributed power stations. H 2 concentration variation is the most influential factor to the hybrid system output power and efficiency, followed by CH 4 , and then CO. System efficiency increases significantly with H 2 concentration increase, while decrease slightly with CO and CH 4 increase. For the system safety operation: ⅰ) when the H 2 and CH 4 fluctuates to relative proportion 90% and 97%, respectively, the reformer will suffer from the potential failure of carbon deposition; ⅱ) when H 2 increases to 116%, the TIT exceeds the upper limit 1223 K, which causes the turbine blade to burn down because of over temperature. For the effect of water variation, the system output power and efficiency will be improved with water reduction, and the efficiency can even reach up to 64.85%. However, the reformer can't work safely due to the severe shortage of water for the reforming reactions. • Study the performance of IT-SOFC/GT hybrid system using gasified biomass gas. • Research safe and load performances of hybrid system with each composition fluctuation. • Investigate safe and load performances of hybrid system with water variation. • Obtain safe operation range of hybrid system for H 2 , CH 4 , CO and H 2 O. [ABSTRACT FROM AUTHOR]

Abstract High fuel utilization (Uf) conditions in a small-scale electrolyte-supported solid oxide fuel cell (SOFC) with an Ni-ScSZ anode were approximated by adjusting the gas composition to correspond to that in the downstream region of an SOFC stack. At Uf = 80%, and with a cell voltage of 0.5 V, the ohmic resistance fluctuated slightly from the early stages of operation, and became much more significant after 80 h. High current density and large polarization were found to promote Ni agglomeration, leading to insufficient connectivity of the Ni nanoparticles. At Uf = 95%, and with a cell voltage of 0.6 V, fluctuations in the polarization were observed at a much earlier stage, which are attributed to the highly humidified fuel. In particular, significant degradation was observed when the compensated anode potential (which incorporates the anode ohmic losses) approached the Ni oxidation potential. Ohmic losses in the anode are considered to influence Ni oxidation by exposing Ni near the electrolyte to a more oxidizing atmosphere with the increase in oxygen ion transport. Stable operation is therefore possible under conditions in which the compensated anode potential does not approach the Ni oxidation potential, assuming a stable interconnected Ni network. Highlights • Ohmic resistance in the anode fluctuated under high current density condition. • Anode polarization fluctuated under highly humidified fuel condition. • Performance fluctuation occurred at around the Ni oxidation potential. • Ohmic loss in the anode affects Ni oxidation. • Stable operation is possible if Ni network is maintained. [ABSTRACT FROM AUTHOR]

This study proposes a novel geometric simulation methodology to estimate the performance of solid oxide fuel cells (SFOCs) electrodes using Monte‐Carlo approach coupled with a statistical algorithm to add infiltrated particles in the form of discrete voxels. Electrochemical performance of these infiltrated electrodes is then characterized by direct evaluation of triple phase boundary (TPB) density and active surface density of the particles. Study results, in agreement with experiment and analytical models, illustrate that there is an optimum point for particle loading, which is strongly depended on the backbone properties and particle aggregation behavior. Study also indicates that the reduction rate of the gas transport factor after adding particles strongly depends on the backbone porosity and the distribution of the particles. Further, it is shown that the average shape of aggregated particles alters the TPB density and gas transport behavior, but particle agglomeration always increases the surface density of particles. Finally, the geometric results are compared with electrochemical tests qualitatively and proposed theories in literature quantitatively. A case study is also performed to compare geometric properties of a realized model with a real reconstructed infiltrated electrode. [ABSTRACT FROM AUTHOR]

A multiscale model is built to understand how microscale characteristics and the thermo‐chemical and electrochemical phenomena, occurring in the electrode and electrolyte assembly, may affect the overall performance of a solid oxide fuel cell (SOFC) stack. This study presents the integration of two‐dimensional finite volume models: a 1D microscale model and a 1D (or 2D) macroscale (channel/cell) model. The new tool is calibrated against the experimental data of a short‐stack via a numerical procedure aiming at the minimisation of the mean square deviation of the model from the measured data. Subsequently, the distribution of electrochemical active thickness in a state‐of‐the‐art solid oxide cell channel is calculated; the result is limited between 3% and 7% of the electrode thickness. An axially graded electrode is studied by changing the particle radii in order to locally control the triple phase boundary length distribution along the cell channel. The performances of a four‐section graded electrode is estimated in comparison to a reference non‐graded electrode. The average current density increases by approximately 6% in the short‐stack. If such a graded design was introduced into a state‐of‐the‐art cogeneration system, the extrapolation of these results suggests that a power output increase up to 13.5% is attainable. [ABSTRACT FROM AUTHOR]

Abstract Fuel cells (FCs) are electrochemical devices that can be used for the direct generation of electrical energy from the chemical energy in fuels with high efficiency, and low or no environmental impact. In particular, high temperature FCs such as solid oxide FCs (SOFCs) are also recognized for their cost-effectiveness and the fact that they can be fed with complex fuels such as methane or biogas which makes them ideal technologies for simultaneous waste treatment and energy generation. Directly fed SOFCs are known as direct internal reforming SOFCs (DIR SOFC) where the reforming of the biogas fuel occurs at the inlet of the cell producing carbon monoxide and hydrogen, which consequently react with oxygen ions along the anode side, and thereby producing electricity. DIR SOFCs integrated with biogas fermenter in wastewater treatment plants or other biological processes offer a window of opportunity for widespread utilization of SOFCs on commercial scale as a green energy source capable of producing several kWs to MWs. However, the performance degradation rate is one of the key issues that directly affects the long-term costs of SOFCs. In addition to the traditional problems, i.e. thermal cycling, oxidation cycling, and incompatibility of components, the DIR biogas SOFC is also affected by the thermal stresses resulting from endothermic reforming reactions and exothermic electrochemical oxidation reactions at the anode surface, the formation of carbon deposits, and the poisoning with impurities such as H 2 S , siloxanes, and halides. This review paper presents an up-to-date summary of the different processes and mechanisms leading to most of the issues encountered with the operation of DIR biogas SOFC, and advises on the methods and strategies that can be applied to mitigate these problems. Graphical abstract fx1 Highlights • Thermal stresses, carbon deposition, and contaminants, are main challenges of DIR biogas SOFC. • Paper-structure anode catalyst is promising for controlling thermal stresses, carbon and sulfur. • CO 2 , air, and/or steam flows is an effective way to control carbon deposition. • Doping Ni with Mo, Cu or CeO 2 is helpful for increasing sulfur tolerance. • Effective temperature should be used in exergy analysis of SOFC to avoid fatal errors. [ABSTRACT FROM AUTHOR]

This study presents a performance prediction of triple combined cycles that use a solid oxide fuel cell (SOFC) and a gas turbine combined cycle (GTCC) with carbon capture technologies. Post- and oxy-combustion capture technologies were comparatively analyzed. The component design parameters of a commercial F-class gas turbine and SOFC were used. Minimizing the turbine inlet temperature (i.e., no extra fuel supplied to the combustor) resulted in higher net cycle efficiency. With post-combustion capture, the net cycle efficiency reached approximately 70 % when no fuel was supplied to the combustor, but the maximum CO2 capture rate was limited to 80 %. When a dual combined cycle was adopted, the CO2 capture rate increased to 91 %, while the net efficiency was approximately 69 %. With oxy-combustion capture, the optimum pressure ratio was higher than in the normal triple combined cycle, and the net cycle efficiency was lower than that of the post-combustion cycle. However, there was a critical advantage of a larger power output with nearly complete carbon capture. The impact of the location of the oxygen supply was examined in the oxy-combustion cycle with extra fuel supplied to the combustor, and supplying all the fuel to the SOFC improved the cycle performance. [ABSTRACT FROM AUTHOR]

Abstract In this work, the effects of an anode functional layer (AFL) with various thicknesses on the physical properties of anode and the electrochemical performance of the anode-supported solid oxide fuel cells (SOFCs) have been systematically studied. Four anode-supported cells with controllable AFL thicknesses have been fabricated by the combined phase-inversion co-tape casting method, screen-printing and dip-coating method. An optimal thickness of the AFL of 7.6 μm is determined by the experimental results including the physical properties and electrochemical performance, and cell performance is significantly enhanced after the introduction of the AFL, which is ascribed to the remarkably increased triple-phase boundaries induced by the AFL. The bilayer anode-supported cells with 7.6 μm thick AFL exhibit a peak power density of 0.906 Wcm−2 and a total resistance of 0.47 Ωcm2 at 700 °C when the anode and the cathode are exposed a humidified H 2 (3 vol% H 2 O) and ambient air, respectively. Additionally, when the anode side is fed with the diluted H 2 (3 vol% H 2 O-97 vol% (10% H 2 –90% N 2)), an excellent peak power density of 0.558 Wcm−2 is still achieved. These results demonstrate that the bilayer anode is a suitable candidate for high-performance SOFC applications, especially at a low hydrogen concentration. Highlights • A bilayer anode is successfully prepared by phase inversion co-tape casting method. • An optimal thickness of anode functional layer is determined to be 7.6 μm. • An excellent peak power density of 0.906 Wcm−2 is obtained at 700 °C. • The bilayer anode is suitable for high-performance SOFC operated at low H 2 content. [ABSTRACT FROM AUTHOR]

Abstract Ammonia appears to be a promising fuel for solid oxide fuel cell systems: it is a carbon-free species, can be stored easily and offers an excellent energy density with a high hydrogen content. This work shows comprehensive investigations of the direct operation of ammonia on an industrial-sized solid oxide fuel cell with Ni/YSZ anode. In the course of this study, ammonia exhibited excellent performance as a fuel for solid oxide fuel cells, although test results equivalent to those of hydrogen/nitrogen fuel mixtures were not attained. Electrochemical impedance spectroscopy proved the reduced performance output of ammonia as fuel to result from its endothermic decomposition. This significantly increased the ohmic resistance, which is mainly influenced by the ammonia flow rate. Operation in counter-flow is more favorable than in co-flow, as lower ohmic and diffusion resistances were measured. Twenty-four-hour stability tests showed stable behavior at 800 °C and a voltage decrease of 2% at 700 °C. Investigations of the anode micro-structure suggest that nickel nitriding occurred, as microscopic pores, particle enlargements, and agglomerations were identified at the metallic parts. Highlights • Measurements of SOFC anode temperature distribution during NH 3 purging. • Identification of the fuel inlet as catalytic active region for NH 3 decomposition. • NH 3 decomposition improves in polarized conditions. • Counter-flow is more favorable than co-flow for direct NH 3 SOFC operation. • NH 3 purging results in micro-structural deformations of Ni/YSZ anodes. [ABSTRACT FROM AUTHOR]

Abstract To expand the processing options for low-temperature-operating solid oxide fuel cells (LT-SOFCs), the hybridization of powder processing and vacuum deposition is attempted. Nanostructured nickel-yttria-stabilized zirconia (Ni-YSZ) anode functional layer (AFL) and YSZ/gadolinia-doped ceria (GDC) bi-layer electrolyte are fabricated over a sintered anode support by pulsed laser deposition (PLD), a physical vapor deposition technology. The most common powder-processed (screen-printed and sintered) La 0.6 Sr 0.4 Co 0.2 Fe 0.8 O 3-δ -Gd 0.1 Ce 0.9 O 1.95 (LSCF-GDC) composite cathode is applied over vacuum-deposited thin-film components. When LSCF-GDC is sintered at a general sintering temperature of 1050 °C then the continuity of the GDC buffer is lost and excessive interdiffusion between the cathode and the electrolyte has occurred at the interface. On the other hand, if the sintering temperature is lowered to 950 °C, peak power density more than 1.7 W cm−2 at 650 °C is obtained. Moreover, the operation stability of the hybrid SOFC (degradation rate ∼8%/100 h) is superior to that of the SOFC with a vacuum-processed nanostructure cathode (degradation rate ∼21%/100 h) when exposed to 0.7 A cm−2 at 650 °C, which is a significantly harsh degradation test condition for LT-SOFCs. [ABSTRACT FROM AUTHOR]

Abstract Based on Aspen Plus, a methanol reforming Solid Oxide Fuel Cell - Humid Air Turbine - Combined cooling, heating and power (SOFC-HAT-CCHP) system based on solar methanol reforming is built in this paper, which combines (Solid Oxide Fuel Cell) SOFC with (Humid Air Turbine) HAT power generation system. This paper analyzes the performance of SOFC-HAT-CCHP system, and reveals the affinity of complementary utilization of solar energy and chemical energy. This paper optimizes the integrated design of the system and constructs a steady state model of the system's thermal calculation. The calculation results show that the total power efficiency of the method, the system total exergy efficiency and the thermal efficiency are 57.2%, 63.0% and 87.1% respectively. The results show that the introduction of HAT power generation system has increased the power generation and reduced the coal consumption rate. Compared with simple methanol reforming (Solid Oxide Fuel Cell - Gas Turbine - Combined cooling, heating and power) SOFC-GT-CCHP, the introduction of HAT effectively improves the total power generation efficiency of the system and increases 4.1% points. The exergy efficiency of increased by 4.6% points. Compared to the reference system, the standard coal consumption rate of electricity generated by the new system decreased by 16.6 g/kWh and the power generation increased by 15.5 g/kWh. Highlights • Present a new type of MR SOFC-HAT-CCHP distributed energy system. • Make use of hydrogen for SOFC from MR through solar energy. • Realize reasonable utilization of different heat energy as well as water recovery. • Conduct the thermodynamic performances through EUD and comparison. [ABSTRACT FROM AUTHOR]

Abstract More/all-electric aircraft is one of the most promising development directions for aircraft. However, the performance of the turbine engine will be strongly affected by the high electric power fraction when the electric power is extracted from the main engine. In order to improve aero-engine performance and electric power fraction, the turbojet engine integrated with an interstage turbine burner (ITB) and solid oxide fuel cell (ITB-SOFC engine) is proposed in this paper. Turbojet engine provides thrust for propulsion and SOFC provides electric power for electrical equipment. In order to evaluate the performance of the ITB-SOFC engine, the thermodynamic analysis model of the engine performance is developed. Analysis results show that the ITB-SOFC engine has advantages in thermal efficiency and specific thrust over the turbojet engine, the increments of these two parameters can reach 2.94% and 23.87% respectively. There is a limitation in pressure ratio for the ITB-SOFC engine, which is 24. The electric power fraction of the ITB-SOFC engine can vary in a wide range. The specific thrust increment over a turbojet engine is high up to 24.07% if the electric power fraction is high up to 0.2. Highlights • The scheme of the turbojet engine integrated with an ITB and SOFC is proposed. • The electric power fraction of the ITB-SOFC engine can vary in a wide range. • The specific thrust increment over a turbojet engine is high up to 24.07%. • The ITB-SOFC engine has advantages in thermal efficiency and specific thrust. [ABSTRACT FROM AUTHOR]

Abstract The performances of Solid Oxide Cells (SOCs) are controlled by key microstructural properties such as the density of Triple Phase Boundary lengths (TPBl) and the interfacial specific surface areas (S i/j). These electrode properties are dependent on basic morphological parameters defined by the phase volume fractions and the Particle Size Distributions (PSD) of the percolated solid phases. The understanding of these relationships is of central importance for designing an optimum electrode microstructure. In this study, semi-analytical expressions for the density of TPBl and the interfacial specific surface areas are investigated. For this purpose, a large number of synthetic microstructures are generated by using validated models based on the sphere packing and the truncated Gaussian random field methods. The coefficients of the parametric equations for both investigated properties (TPBl density and S i/j) are fitted on the large database generated. The predictions of the microstructural correlations are in good agreement with the parameters directly computed on 3D reconstructions of typical LSCF-CGO and Ni-YSZ electrodes, thereby validating their reliability. Highlights • Microstructural correlations for specific surface area and triple phase boundary lengths. • Calibration of the semi-analytical relationships on a large dataset of synthetic microstructures. • Validation of the semi-analytical correlations on 3D reconstructions. [ABSTRACT FROM AUTHOR]

Highlights • Innovative carbon removal and performance restoring approaches. • Optimization of the regeneration methods. • Suggestions about commercial application of individual methods. • Lifetime extension proposal for SOFCs. Abstract Carbon deposition is one of the major degradation sources, which reduces the activity of solid oxide fuel cells (SOFC) and it can even cause irreversible cell degradation. In order to counteract this phenomenon and thus to extend the SOFC lifetime, development of effective cell-protecting strategies for carbon re-gasification and restoring of the cell performance is of crucial importance, since other methods considering prevention of this degradation phenomenon can mean an increased system complexity or reduced system performance. In the literature there is very limited data relating to the performance of SOFCs after the carbon removal process has been executed. This study aims to analyze carbon removal techniques and moreover their effect on the SOFC performance as well as possibilities for industrial application. Various innovative approaches for carbon re-gasification are scrutinized and detailed explained within this study on 20 samples, which further help to provide potential carbon removal procedures relevant for industrial SOFC systems. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Porous symmetric YSZ electrolyte support was fabricated by phase inversion. • Nanostructure PBMO electrode was obtained by infiltration. • Both anode and cathode interfacial resistances were greatly decreased. Abstract A symmetric solid oxide fuel cell based on yttrium stabilized zirconia (YSZ) electrolyte and PrBaMn 2 O 5+δ (PBMO) electrode was developed by phase inversion and infiltration methods. Symmetric electrolyte support composed of two porous backbones and a thin dense layer were obtained by phase inversion and drop-coating techniques. PBMO catalysts were infiltrated into the finger-like pores of the backbone to serve as electrodes. Scanning electron microscopy results show that the cell has a porous symmetric structure with nanosized PBMO catalysts distributed in finger-like microchannels. With this symmetric structure, the anode polarization resistance for the cell decreased by 46% and the cathode polarization resistance decreased by 39% at 800 °C. The power outputs were improved by 100% in H 2 and CH 4 fuel gas at 800 °C. These results imply that optimizing the microstructure of the electrolyte support is a promising approach to increase active surface areas and further improve the cell performance for SOFCs. [ABSTRACT FROM AUTHOR]

Abstract A three-dimensional (3-D) model for planar, anode-supported, solid oxide fuel cell (SOFC) is developed to investigate the effect of operating pressure on cell characteristics. The results show that the elevated operating pressure can improve cell performance by increasing open circuit voltage and reducing activation overpotential, and enhance the electrochemical reaction in the vicinity of electrolyte. Besides, the high pressure can also change the distributions of species and internal reforming reactions. Compared to the case using syngas as fuel, the operating pressure has more significant effects on temperature gradient along flow direction when partly pre-reformed gas is supplied. In addition, efficient control of cell temperature could be achieved by decreasing fuel utilization in the case of partly pre-reformed gas, but this is achieved at the expense of cell efficiency, especially under high pressure condition. Another way to reduce the temperature gradient is to adopt higher air ratio. Moreover, when partly pre-reformed gas is used, the counter-flow configuration has a better performance due to the higher overall temperature. Highlights • A 3D model for SOFC is developed considering influence of pressure. • The model is validated on temperature and pressure effects. • High pressure can significantly improve SOFC output performance. • High pressure enhances chemical and electrochemical reactions. • Fuel utilization affects temperature distribution with partly pre-reformed gas. [ABSTRACT FROM AUTHOR]

Abstract Proton-conducting reversible solid oxide cells (PC-RSOCs) have attracted extensive attention due to their high efficiencies as energy conversion devices. Generally, the performance of the cell is affected to a certain extent by the microstructure of the electrodes, which is closely related to the gas diffusion and surface reaction processes. Herein, different contents of the carbon microspheres (CMSs) are used as the pore formers to control the microstructure of the hydrogen electrode. Experimental results reveal that the porosity, line shrinkage, and thermal expansion coefficient of the hydrogen electrode support simultaneously increase with the CMS content. The support with 30 wt% CMS presents high porosity (39.27 vol%) with uniform-size pores. Subsequently, the corresponding single cells were fabricated successfully, particularly, the cell with 30 wt% CMS exhibiting the best electrochemical performance in both fuel cell (0.46 W cm−2 at 700 °C) and electrolysis cell (1.41 A cm−2 at 1.3 V and 700 °C) operational modes. Further results demonstrated the highest performance was attributed primarily to the maximal three-phase boundary length, which mainly originates from the high porosity and unique microstructure of the hydrogen electrode. Highlights • Different contents of CMS were used as pore former for the hydrogen supports. • The support with 30 wt% CMS possesses high porosity with uniform-size pores. • The performances of corresponding cells in reversible SOFC/SOEC modes were studied. • The cell with 30 wt% CMS showed the best electrochemical performance. [ABSTRACT FROM AUTHOR]

The change in the mechanical and electrochemical performance of tape cast YSZ electrolyte as a function of doctor blade gap is investigated in this study via mechanical, microstructural and electrochemical analyses. Three point bending tests indicate that the flexural strength of the electrolyte can be improved by reducing the doctor blade gap. This can be elucidated by the microstructural observations, which reveal an increased number of small grains and reduced grain size with decreasing the doctor blade height, confirming the sintering shrinkage. The impedance results reveal that the electrical resistance of the electrolyte increases with decreasing the doctor blade gap due to reduced grain size. Similar behavior is also observed in the performance results. Therefore, the doctor blade gap can be considered as a critical parameter for the mechanical and electrochemical performance of tape cast YSZ electrolyte in solid oxide fuel cells, since it significantly affects the electrolyte microstructure. [ABSTRACT FROM AUTHOR]

Abstract This study investigates the proper configuration of an electric propulsion system for a very large ethane carrier. The system consists of a dual-fuel diesel electric generator and a solid oxide fuel cell-gas turbine hybrid system to replace the mechanical propulsion system based on a marine diesel engine. When the ship navigates the open sea, the dual-fuel diesel electric generator and hybrid system run in parallel at a power rating of 16 MW. However, the hybrid system only operates during the berthing state for ship hoteling. The system efficiency, energy efficiency design index, and availability are considered to identify the optimal system configuration. When the dual-fuel diesel electric generator produces 10 MW, the hybrid system generates 6 MW. Because the electric propulsion system complies with international environmental regulations, it may be broadly acceptable for gas carriers in terms of eco-efficiency. The system achieves high availability by using fault tree analysis and minimal cut sets. Highlights • An electric propulsion system can replace mechanical propulsion machinery in a gas carrier. • An SOFC-gas turbine system solely generates electricity for ship hoteling service. • The marine generator-SOFC-gas turbine system satisfies the CO 2 regulation. • The availability of a hybrid system is high on maneuvering and berthing states. Graphical abstract Image 1 [ABSTRACT FROM AUTHOR]

In the present study, an efficient approach for the prediction of Warburg-type element is proposed via the analysis of the anode-supported solid oxide fuel cell (SOFC) performance under various working conditions. The details of the performance, polarization curves, impedance behavior, and species distribution profiles within the electrode are investigated via the combination of equivalent circuit model (ECM) analysis and multiphysics numerical simulations. The multiphysics simulation is developed and calibrated with experimental results of SOFC button cells under various working currents. With the complete datasets generated from the calibrated simulations, the trends of the element parameters involved in equivalent circuit model are analyzed. Generalized empirical functions are proposed as well as the procedures of prediction of performance under different conditions. The verification cases show good agreement between the predicted results from proposed model and the reference results. This proposed approach can be utilized to quickly predict the properties for desired performance in the manufacturing processes, and it also has the potential of reducing the computational cost in the simulation of large SOFCs. [ABSTRACT FROM AUTHOR]

Degradation rates of electrical current during constant voltage operation of SOFCs with anodes made using NiO precursor powders from two different manufacturers with and without the addition of aluminum titanate (ALT) added by either mechanical mixing or anode infiltration have been quantified using a novel MATLAB algorithm. Because the algorithm has been used to quantify degradation rates for many different SOFC tests, it is thought that the method can be applied to most measured SOFC data to quantify the instantaneous cell degradation rate as a function of time for the entire SOFC performance measurement. Degradation rates determined at different times have been plotted against varying concentrations of ALT addition, facilitating the estimation of optimum ALT concentration for SOFC anodes made with NiO from a specific manufacturer. The algorithm used to determine degradation rates is available upon request to the corresponding author. [ABSTRACT FROM AUTHOR]

Novel NiCo2O4 nanoarrays have been in-situ grown on a La0.8Sr0.2MnO3-δ(LSM) cathode through a hydrothermal method, which presents the enhanced electrochemical performances of the LSM cathode for the intermediate temperature solid oxide fuel cells. XRD and SEM have been used to characterize phase structure and morphology of NiCo2O4 nanoarrays. The LSM cathode, modified by the NiCo2O4 nanoarrays, exhibits excellent electrochemical performances compared with the bare LSM cathode. The maximum peak power density of single cell, based on the NiCo2O4 nanoarrays modified the LSM cathode, reaches 957 mW cm−2 at 800 °C, which is almost two times higher than that for the cell based on the bare LSM cathode. [ABSTRACT FROM AUTHOR]

The performance of Solid Oxide Fuel Cells (SOFCs) is highly sensitive to the fluid dynamics, the interfacial areas, and the residence time of the gases. These parameters are primarily dictated by the geometry of the channels carrying the fuel and the oxidant. However, not many investigations have been made to study the effect of bipolar plate designs on cell performance. We report a detailed comparative study of the performance characteristics of straight and serpentine channel geometries. Simulations of these two channels have been made taking into account fluid flow through the channels and the porous electrodes, multicomponent diffusion, heat transfer, charge transfer reaction kinetics and electrodynamics. Performance of each channel has been compared to in-house experimental data. Extensive parametric analyses have been carried out to evaluate the dependence of cell performance on fuel and air flow rates. Favourable operating ranges of hydrogen and air feeds have been estimated analytically taking into account fuel utilisation, cell temperature, channel pressure drops, and current density. It has been shown that serpentine geometries offer remarkably more uniform distribution of ionic current density, and significantly higher power output and fuel utilisation compared to straight channel geometries. However, these are accompanied by a penalty of pressure drop. This analysis can provide a useful guideline for selecting the channel geometry. [ABSTRACT FROM AUTHOR]

Lowering operation temperature of the solid oxide fuel cell is critical to improving its reliability and durability. However, the tradeoff between the operation temperature and the oxygen reduction reaction on the cathode side hinders lowering of the operation temperature. To address this issue, we employ a nano-web-structured La 0.6 Sr 0.4 Co 0.2 Fe 0.8 O 3-δ (NW-LSCF) thin-film layer as an interlayer on the cathode side. This thin-film layer enables operating the cell at a low temperature with enhancement of the electrochemical performance by increasing the oxygen-reduction reaction site and is fabricated via a simple spin-coating method. The large surface area of NW-LSCF enables significant improvement in the oxygen reduction reaction by an increased triple-phase boundary. In addition, the adhesion property between the gadolinium-doped ceria electrolyte and cathode is improved by the layer. In an anode-support-type single cell test, the peak power density of the cell with NW-LSCF is 0.57 W/cm 2 at 550 °C, which is an approximately 63% improvement compared to that of the cell without NW-LSCF. Moreover, the value is comparable to the peak power density of the cell without NW-LSCF operating at 600 °C. This finding suggests the possibility of lowering the operating temperature of the solid oxide fuel cell by introducing NW-LSCF into the cell. [ABSTRACT FROM AUTHOR]

A symmetrical solid oxide fuel cell (SOFC) with a novel microstructure of BaZr 0.9 Y 0.1 O 3–δ (BZY) as the electrolyte is investigated in this study. The cell with the Ni 0.8 Co 0.15 Al 0.05 LiO 2 (NCAL)-foam Ni/BZY/foam Ni-NCAL structure is prepared by a co-pressing method. The maximum obtained power density is 735.6 mW cm −2 in H 2 at 550 °C, which is comparable to the results obtained using Ni cermet anode-supported SOFCs with an extremely thin electrolyte. The ionic conductivity of the BZY electrolyte prepared in this study is much higher than that of the conventional BZY electrolyte. The activation energy of ionic conduction is much lower than that of traditional oxygen ion or proton conduction. Electrochemical impedance spectra (EIS) results of the cell with the BZY electrolyte measured in different atmospheric conditions and the results of oxygen ion filtration experiments for the cell using the BZY/Ce 0.9 Gd 0.1 O 2 (GDC) bilayer electrolyte indicate that oxygen ion is one of the carriers in the BZY electrolyte prepared in this study. According to the results of X-ray photoelectron spectroscopy (XPS) and Fourier Transform infrared spectroscopy (FTIR), an interfacial O 2− conduction mechanism at the interface of BZY particles in the electrolyte is discussed. [ABSTRACT FROM AUTHOR]

PdO/ZrO 2 co-infiltrated (La 0.8 Sr 0.2 ) 0.95 MnO 3-δ -(Y 2 O 3 ) 0.08 (ZrO 2 ) 0.92 (LSM-YSZ) composite cathode (PdO/ZrO 2 +LSM-YSZ), which adsorbs more oxygen than equal amount of PdO/ZrO 2 and LSM-YSZ, is developed and used in Ni-YSZ anode-supported cells with YSZ electrolyte. The cells are investigated firstly at temperatures between 650 and 750 °C with H 2 as the fuel and air as the oxidant and then polarized at 750 °C under 400 mA cm −2 for up to 235 h. The initial peak power density of the cell is in the range of 438–1207 mW cm −2 at temperatures from 650 to 750 °C, corresponding to polarization resistance from 1.04 to 0.35 Ω cm 2 . This result demonstrates a significant performance improvement over the cells with other kinds of LSM based cathode. The cell voltage at 750 °C under 400 mA cm −2 decreases from initial 0.951 to 0.89 V after 170 h of current polarization and remains essentially stable to the end of current polarization. It is identified that the self-limited growth of PdO particles is responsible for the cell voltage decrease by reducing the length of triple phase boundary affecting the high frequency steps involved in oxygen reduction reaction in the cathode. [ABSTRACT FROM AUTHOR]

The electrochemical performance of layered Ni 0.8 Cu 0.2 /Ce 0.8 Gd 0.2 O 1.9 (GDC) cermet anodes is investigated for intermediate-temperature solid oxide fuel cells (IT-SOFCs) at 600 °C using humidified (3% H 2 O) model syngas with a molar ratio of H 2 /CO = 3/2 as the fuel. From the results obtained, the electrochemical performance of the functionally graded multi-layered anodes is found to be superior to the mono-layered anodes. The test cell with a bi-layered anode consisting of 100 mass% Ni 0.8 Cu 0.2 /0 mass% GDC (10M/0E) and 70 mass% Ni 0.8 Cu 0.2 /30 mass% GDC (7M/3E) exhibits high power density. The test cell with a tri-layered anode consisting of 10M/0E, 7M/3E, and 50 mass% Ni 0.8 Cu 0.2 /50 mass% GDC (5M/5E) exhibits an even higher power density, suggesting that 10M/0E and 5M/5E layers contribute to the current collecting part and active part, respectively. [ABSTRACT FROM AUTHOR]

The development of carbon- and sulfur-tolerant anode materials is highly desirable for the commercial application of solid-oxide fuel cells (SOFCs). We report herein the performance of Sr 1.9 VMoO 6− δ (SVMO) double perovskite as a potential anode material for SOFCs and the improvement of its electrochemical performance on hydrogen and H 2 S-containing syngas operation. SVMO has a cubic structure and thermal expansion coefficient of 13.3 × 10 −6  K −1 between 30 and 1000 °C in 5% H 2 /Ar. The electrical conductivities of SVMO in H 2 are considerably higher than those of existing double-perovskite anodes and traditional Ni–YSZ (40 vol% Ni) anode. The impregnation of Pd nanoparticles to form a composite anode (Pd–SVMO) or the addition of a Ce 0.8 Sm 0.2 O 1.9 buffer layer between anode and electrolyte significantly improves the electrochemical performance of SVMO for hydrogen oxidation, and the former is considerably more effective than the latter. The Pd–SVMO composite anode exhibits good stability and resistance to carbon deposition and sulfur poisoning for an SOFC operated on H 2 S-containing syngas based on an 80 h test, suggesting the potential of this anode material for SOFCs running on hydrocarbon fuels. The mechanisms for improving the electrochemical performance of the anodes and the resistance to carbon deposition and sulfur poisoning are also discussed. [ABSTRACT FROM AUTHOR]

The electrochemical reaction efficiency for an SOFC is determined mainly at the interfaces between electrodes and electrolyte. The cell performance is influenced by a variety of parameters, such as the particle size, porosity, and microstructure. Microstructural tuning in the electrodes hence provides the performance elevation by increase the effective interfacial reaction sites. In this study, we use traditional materials to form the cells constructed with NiO-YSZ (Yttria stabilized zirconia) as anode supported substrate, YSZ as electrolyte, and YSZ-La0.8Sr0.2MnO3 (LSM) | LSM as functional and cathode layers. In the anode, two different cermet structures with powder refinement approach have been adopted to increase the oxygen exchange rate. On the other hand, introducing LSM-YSZ composite as functional layer is essential for the limited ion conductivity of LSM, which will be beneficial for power output. The cell performance elevation and microstructure analysis allows us to verify functions of sub-micron cermet at anode during the cell operation. The composition effect in cathode may also favor the enhancement. Three typical cells were prepared, and the maximum power density is 280 mWcm-2 for cell with original materials used. The power density increases to 395 mWcm-2 for the cell with cermet particle refinement. It further improves to 520 mWcm-2 for cell with cathode functional layer modification. The small grain size of several tens nano-meter structure in the interfaces exists in a local region near interfaces. It is evidenced that the nano-sized electrode materials which may be attributed to the high current loading can increase the triple phase boundary (TPB) density. [ABSTRACT FROM AUTHOR]

Degradation of a solid oxide electrolysis cell (SOEC) during long-term operation remains to be the key obstacle to their massive production and commercialization. One of degradation processes within SOEC is anode delamination. The anode of SOEC splits at the interface with solid electrolyte due to elevated pressure of oxygen that is produced by electrochemical reactions. The main assumption that anode delamination starts at the fuel inlet is based on post-mortem analysis of SOEC. This paper addresses numerical modelling of a single, electrolyte supported, SOEC. The anode delamination is modelled by implementing the modifications of SOEC's geometry. A brief overview of the model is also given. Verification of the implemented model relies on the measurement data from literature. The simulation results show that increasing the area of delaminated anode ( A delaminated ) increases the operating voltage of the SOEC if a constant electrolysis current is applied. This strongly influences the conversion efficiency (η) of the SOEC. Indeed, if linear growth of A delaminated over time is assumed, the η of SOEC degrades very fast at the beginning of SOEC's operation. The presented model also helps analyze the hot spots of current density, where high pressure of oxygen appears. [ABSTRACT FROM AUTHOR]

Two 5-cell solid oxide fuel cell (SOFC) stacks with an external manifold structure are constructed and their degradation and thermal cycle performance are investigated at 750 °C. The cell consists of anode-supported cells with a size of 11 × 11 cm. In Stack A, the voltage degradation rate during 140 h tests at a current density of 400 mA/cm 2 is about 50%/1000 h. The factors influencing the performance of stack are investigated by post-test analysis. We found partial decomposition of the cathode contact materials LaCo 0.6 Ni 0.4 O 3-δ and higher oxidation rate of metallic interconnect, resulting in an increase of the electrical resistance of the stack. Owning to the improvement of suitable sealing materials and interconnect, the resulting Stack B exhibited reasonable degradation rate of about 5%/1000 h during 140 h at a current density of 500 mA/cm 2 together with a good thermal cycle stability. The applicability of stacks with an external manifold structure can be demonstrated in planar intermediate temperature SOFC. [ABSTRACT FROM AUTHOR]

Oxide-ion conductors play a significant role in various applications such as solid oxide fuel cells (SOFCs), oxygen separation membranes and sensors. Recently, high ionic conductivity (~ 1 × 10 − 4 S cm − 1 at 600 °C) was found in sodium bismuth titanate (NBT), which originates from oxygen vacancies compensating the introduced Bi-deficiency. By providing pathways with low diffusion barriers, the highly polarizable Bi 3 + ions with 6s 2 lone pair electrons and weak Bi O bonds are also beneficial for the migration of oxygen ions. Here we report the influence of lithium doping on the electrical properties of NBT. The optimal doping level of 4 at% Li on the Bi-site improves the ionic conductivity by one order of magnitude to ~ 7 × 10 − 3 S cm − 1 at 600 °C without changing the conduction mechanism, which could be attributed to an increase in the oxygen vacancy concentration based on an acceptor doping mechanism. A further increase in Li content does not improve the total conductivity. Oxygen diffusion data were acquired by the Isotope Exchange Depth Profile (IEDP) method in combination with Secondary Ion-Mass Spectrometry (SIMS). The oxygen self-diffusion coefficients (e.g. 7.04 × 10 − 9 cm 2 s − 1 at 600 °C) are in excellent agreement with the values derived from impedance spectroscopy data, suggesting that the oxygen ions are the main charge carriers in the system. Furthermore, a degradation test was performed for 100 h under a variety of atmospheres, showing only a slight decrease in conductivity in both air and oxygen atmospheres attributed to the loss of material from the A-site. Comparison with other oxide-ion conductors indicates that Li-doped NBT materials are promising candidates for intermediate temperature SOFC applications. [ABSTRACT FROM AUTHOR]

The novel Cl − -doped compound based on oxygen deficient double perovskite Ba 2 CaNbO 5.5 was synthesized Ba 2 CaNbO 5.48 Cl 0.05 and its structure, thermal properties, hydration behavior and electrical properties have been investigated. It was found that introduction of Cl − ions leads to the increasing of oxygen ion and proton conductivities. The appearance of donor defect Cl o (or F o ) decreases the activation energy for oxygen ion transport and increases the mobility of oxygen vacancies due to electrostatic repulsion between the positive charged defects V o and Cl o (F o ). It was shown that Cl − -doping decreases proton concentration but enhances proton conductivity due to significant increase in proton mobility. [ABSTRACT FROM AUTHOR]

A slight Nb 2 O 5 co-doping in 11Sc 2 O 3 -89ZrO 2 was earlier reported to stabilize the high-symmetry cubic phase completely and enhances the conductivity significantly. The present work looked at the temporal stability of conductivity in 1Nb 2 O 5 -10Sc 2 O 3 -89ZrO 2 (1Nb10ScSZ) for the electrolyte application in solid oxide fuel cells. In-situ conductivity measurement was done using impedance spectroscopy at 650 °C in the air for 2000 h. A substantial conductivity loss (29%) was observed in the first 1000 h. Following which, conductivity remained relatively stable for the next 1000 h. Impedance analysis showed that the main contribution to the conductivity degradation was from grain conductivity. Phase analysis performed using XRD, TEM and Raman spectroscopy revealed that both the unaged and aged 1Nb10ScSZ samples consisted of metastable t″-phase. However, the extent of tetragonality was found to increase after ageing. The formation of low-symmetry phase was suggested to be the reason for the grain conductivity loss in 1Nb10ScSZ. [ABSTRACT FROM AUTHOR]

In this study, the effects of Cu-ion substitution on the densification, microstructure, and physical properties of LaCo 0.4 Ni 0.6-x Cu x O 3-δ ceramics were investigated. The results indicate that doping with Cu ions not only enhances the densification but also promotes the grain growth of LaCo 0.4 Ni 0.6-x Cu x O 3-δ ceramics. The Cu substitution at x ≤ 0.2 can suppress the formation of La 4 Ni 3 O 10 , while the excess Cu triggers the formation of La 2 CuO 4.032 phase. The p-type conduction of LaCo 0.4 Ni 0.6 O 3-δ ceramic was significantly raised by Cu substitution because the acceptor doping ( C u N i ' ) triggered the formation of hole carriers; this effect was maximized in the case of LaCo 0.4 Ni 0.4 Cu 0.2 O 3-δ composition (1480 S cm −1 at 500 °C). Thermogravimetric data revealed a slight weight increase of 0.29% for LaCo 0.4 Ni 0.4 Cu 0.2 O 3-δ compact up to 871 °C; this is due to the incorporation of oxygen that creates metal vacancies and additional h • carriers, partially compensating the conductivity loss due to the spin-disorder scattering. As the temperature of the LaCo 0.4 Ni 0.4 Cu 0.2 O 3-δ compacts rose above 871 °C, significant weight loss with temperature was observed because of the release of lattice oxygen to the ambient air as a result of Co (IV) thermal reduction accompanied by the formation of oxygen vacancies. A solid oxide fuel cell (SOFC) single cell with Sm 0.2 Ce 0.8 O 2-δ (electrolyte) and LaCo 0.4 Ni 0.4 Cu 0.2 O 3-δ (cathode) was built and characterized. The Ohmic (0.256 Ω cm 2 ) and polarization (0.434 Ω cm 2 ) resistances of the single cell at 700 °C were determined; and the maximum power density was 0.535 W cm −2 . These results show that LaCo 0.4 Ni 0.4 Cu 0.2 O 3-δ is a very promising cathode material for SOFC applications. [ABSTRACT FROM AUTHOR]

Rare-earth-doped CeO 2 have been found to enhance the ionic conductivity of ceria-based electrolytes in solid oxide fuel cells (SOFCs) because trivalent rare-earth cations can spontaneously induce oxygen vacancies. Experimentally, it has been shown that the rare-earth elements La, Nd, Sm, Gd, Tb, Dy, and Er are likely candidates for electrolyte doping. However, the performances differ for the trivalent cations, suggesting that rare-earth doping plays multiple roles instead of only increasing the oxygen vacancies. First-principles calculations are performed on a series of rare-earth-doped CeO 2 systems to study the doping effects on the ionic conductivity. It is found that the migration barriers of the oxygen ions are significantly different for the different dopants and depend on the dopant's radius. Gd-, Dy-, Er-, and Tb-doping results in small migration barriers and enhances the ionic conductivity. We also calculate the formation energies ( E vac ) of the intrinsic oxygen vacancies due to thermal excitation. It is found that the Sm- and Gd-doped ceria systems have the smallest E vac values. The electronic structures indicate that the band gaps are not sensitive to the dopant elements but are very sensitive to the fluctuations in the oxygen content. [ABSTRACT FROM AUTHOR]

Several proton conductive ceramic oxides are evaluated for potential application in ceramic-NiO composite anodes for proton-conducting La 0.99 Ca 0.01 NbO 4 (LNO) electrolyte-based fuel cells. Chemical compatibility tests show that most of the existing proton-conducting oxides are unfavorable for application in LNO electrolyte-based fuel cells because of undesirable reactions at high temperatures. Further considering the chemical compatibility with NiO and the ability to promote the densification of the deposited LNO electrolyte, LNO-NiO composite anode proves to be the only suitable anode candidate. With humidified hydrogen (∼3%H 2 O) as the fuel and static air as the oxidant, fuel cells based on LNO electrolyte film deposited on LNO-NiO anodes show a peak power density of 24 mW cm −2 at 750 °C, this value being one of the largest ever reported for LNO-based cells. Further investigation reveals that the polarization resistance of the cell is the major contribution to the total cell resistance, limiting the overall cell performance. [ABSTRACT FROM AUTHOR]

Proton-conducting solid oxide fuel cells (H + -SOFCs) have attracted considerable interest recently. However, the overall cell performance of H + -SOFCs is still low due to the lack of a promising cathode material. In this study, SrSc 0.175 Nb 0.025 Co 0.8 O 3-δ (SSNC) was synthesized for evaluation as a cathode material in H + -SOFCs based on a BaZr 0.1 Ce 0.7 Y 0.2 O 3-δ (BZCY) electrolyte. The chemical compatibility and stability of the SSNC cathode with the BZCY electrolyte in humidified air were studied. In addition, the electrochemical behavior of the SSNC cathode on the BZCY electrolyte was investigated using SSNC/BZCY/SSNC symmetrical cells at 600 °C in dry air and humidified air at various H 2 O partial pressures. Promising electrocatalytic activity was observed for the SSNC cathode in humidified air. The area specific resistance obtained on symmetrical cells at 600 °C in a 10% H 2 O-air atmosphere was 0.26 Ω cm 2 . A promising peak power density of 498 mW cm −2 was obtained using an anode-supported cell with a 46 μm-thick BZCY electrolyte layer at 700 °C. [ABSTRACT FROM AUTHOR]

Development of low-temperature solid oxide fuel cells (SOFCs) is crucially important for their stable and continuous operation as a reliable power source. With Ni nanoparticles impregnated into the thick anode support, Sr and Mg doped LaGaO 3 (LSGM) based electrolyte has been demonstrated to be adept at reducing the ohmic resistance for high performance at low temperatures (450–650 °C). In this study, 55-μm LSGM-electrolyte-based SOFCs are prepared via the impregnation for both cathode and anode, and high performance is obtained at low temperatures. The durability and reduction-oxidation (redox) stability are examined in terms of the calcination temperature of LSGM/Ni(O) anode that determines the thermal growth of NiO crystals and interfacial reaction between NiO and LSGM. We find that the cell with anode calcined at 1100 °C does contain larger NiO grains and more secondary phases, but it shows similar power density comparing to the one calcined at 800 °C. Both cells are stable at 650 °C and no damage on the electrolyte is found during the redox cycle, but the performance of the former is more sensitive to the redox cycle due to the high ohmic resistance arisen from the possible discontinuous connection between the large Ni grains. [ABSTRACT FROM AUTHOR]

High temperature water electrolysis with solid oxide electrolysis cells (SOECs) is a promising method for hydrogen production. In order to study the performance and degradation behavior of cells with different cell components in electrolysis mode, a four-cell stack was assembled that used JÜLICH's F10 design with two types of air electrodes based on La 0.6 Sr 0.4 CoO 3−δ (LSC) and La 0.6 Sr 0.4 Co 0.2 Fe 0.8 O 3−δ (LSCF). A PVD-prepared GDC layer was applied to LSCF cells while a screen-printing GDC layer was used in the LSC cells. The performance of the stack was first characterized with IV-curve measurements in both SOFC and SOEC modes within the temperature range of 700–800 °C. The durability of the stack was investigated by conducting a long-term stationary electrolysis operation with a constant current density of −0.5 Acm −2 and steam conversion rate of 50% at 800 °C. Electrochemical Impedance Spectroscopy (EIS) was used to study the electrochemical performance of the stack, as well as the degradation behavior during long-term electrolysis operation. The method “Distribution of Relaxation Times” (DRT) was applied for the further analysis of the EIS data, and the DRT results have successfully supported the stack degradation analysis. [ABSTRACT FROM AUTHOR]

Cobalt-free provskite oxides Bi 0.5 Sr 0.5 Fe 1− x Nb x O 3− δ (BSFN x , x = 0.05, 0.10 and 0.15) were prepared and evaluated as cathode materials for intermediate temperature solid oxide fuel cells (IT-SOFCs). In particular, the effects of Nb substitution on phase evolution, thermal expansion behavior and electrochemical performance were systematically investigated. The average thermal expansion coefficient (TEC) of BSFN x decreases from 13.3 × 10 −6 K −1 at x = 0.05 to 12.6 × 10 −6 K −1 at x = 0.15 within a temperature range of 50–800 °C. Among the BSFN x materials, Bi 0.5 Sr 0.5 Fe 0.9 Nb 0.1 O 3− δ (BSFN0.10) oxide shows the best electrochemical performance. The polarization resistances ( R p ) of BSFN0.10 cathode on CGO electrolyte are 0.038, 0.075 and 0.156 Ω cm 2 at 700, 650 and 600 °C, respectively. Meanwhile the maximum power densities of the anode-supported single cells are 1.28, 1.54 and 1.34 W cm −2 at 700 °C for BSFN x cathodes with x = 0.05, 0.10, and 0.15, respectively. Furthermore, the relationship study of oxygen partial pressure dependence on R p indicates that the oxygen reduction reaction (ORR) rate-limiting step is the oxygen adsorption-dissociation on the electrode surface. The desirable electrochemical performance demonstrates that BSFN x oxides are potential cathode materials for IT-SOFCs. [ABSTRACT FROM AUTHOR]

The need to experimentally understand the detailed performance of SOFC stacks under operating conditions typical of commercial SOFC systems has prompted this two-part study. The steady state performance of a 6-cell short stack of yttria (Y 2 O 3 ) stabilised zirconia (YSZ) with Ni/YSZ anodes and composite Sr-doped lanthanum manganite (LaMnO 3 , LSM)/YSZ cathodes is experimentally evaluated. In Part A, the stack characterisation is carried out by means of sensitivity analyses on the fuel utilisation factor and the steam-to-carbon ratio. Electrical and environmental performances are assessed and the results are compared with a commercial full-scale micro-CHP system, which comprises the same cells. The results show that the measured temperature dynamics of the short stack in a test stand environment are on the order of many minutes; therefore, one cannot neglect temperature dynamics for a precise measurement of the steady state polarisation behaviour. The overall polarisation performance is comparable to that of the full stack employed in the micro-CHP system, confirming the good representation that short-stack analyses can give of the entire SOFC module. The environmental performance is measured verifying the negligible values of NO emissions (<10 ppb) across the whole polarisation curve. [ABSTRACT FROM AUTHOR]

The need to experimentally understand the performance of Solid Oxide Fuel Cells (SOFC) stacks under Carbon Capture and Storage (CCS) mode operating conditions, hence with anode recirculation, has prompted this two-part study. The steady state performance of a 6-cell short stack of Y 2 O 3 stabilised Zirconia (YSZ) with Ni/YSZ anodes and composite Sr-doped LaMnO 3 (LSM)/YSZ cathodes is experimentally evaluated. In Part A, the electrical and environmental performance are assessed and the results are compared with the commercial full-scale micro-Combined Heat and Power system, which comprises the same cells. In Part B of this work, a specific set of stack operating conditions important to CCS applications is explored. The experimental inlet composition is changed in order to reproduce a simulated syngas in CCS mode operation for different fuel utilisation factors. Operation with the simulated anode recycle syngas leads to lower voltage when the anode recycle is lower, mainly due to higher internal reforming and polarisation losses. A clear voltage trend is observed when the amount of CO content in the inlet fuel is increased, signalling an improvement of the polarisation performance at constant current density and fixed inlet equivalent hydrogen content. Stack degradation is measured and results in line with manufacturer's data. [ABSTRACT FROM AUTHOR]

A novel reactor of a natural gas (NG) fueled, 1 kW net power solid oxide fuel cell (SOFC) system with anode off-gas recirculation (AOGR) is experimentally investigated. The reactor operates as pre-reformer, is of the type radial reactor with centrifugal z-flow, has the shape of a hollow cylinder with a volume of approximately 1 L and is equipped with two different precious metal wire-mesh catalyst packages as well as with an internal electric heater. Reforming investigations of the reactor are done stand-alone but as if the reactor would operate within the total SOFC system with AOGR. For the tests presented here it is assumed that the SOFC system runs on pure CH 4 instead of NG. The manuscript focuses on the various phases of reactor operation during the startup process of the SOFC system. Startup process reforming experiments cover reactor operation points at which it runs on an oxygen to carbon ratio at the reactor inlet ( ϕ RI ) of 1.2 with air supplied, up to a ϕ RI of 2.4 without air supplied. As confirmed by a Monte Carlo simulation, most of the measured outlet gas concentrations are in or close to equilibrium. [ABSTRACT FROM AUTHOR]

Issues related to SOFCs performance and durability are strictly dependent on the feeding fuel quality. SOFC capability to be fed with fuels different from hydrogen opens to scenarios in which a big variety of fuels can be used at the aim. Unfortunately, problems related to anode deactivation due to the contaminants presence can arise. The present work investigates the performance of anode supported solid oxide fuel cells in case of co-feeding of different trace compounds. Electrochemical impedance spectroscopy is the investigation technique used to analyze the impedance spectra. Typical biogas from OFMSW trace contaminants that follow an initial failure in the cleaning system, such as sulphur, aromatic compounds and siloxanes, have been simultaneously tested. Tests showed that the most deleterious impact for the SOFC was due to the H 2 S action. This influences mostly the electrochemical losses respect to diffusion losses, even if this last are not null and can be accounted as a secondary effect. On the contrary, the co-presence of D4 and H 2 S mitigates in the short-term the effect that the only D4 produces when fed with biogas. The most relevant consequence produced by C 7 H 8 was recorded in the low frequency of Nyquist plot, affecting mainly the mass transport phenomena. Experimental tests are accompanied by the implementation of the fuel cell model through COMSOL Multiphysics software to study the effect of pollutants on fuel cell performance. [ABSTRACT FROM AUTHOR]