Solid Oxide Fuel Cell Applications Research Articles

Enhancing the Catalytic Activity and Coking Tolerance of the Perovskite Anode for Solid Oxide Fuel Cells through In Situ Exsolution of Co-Fe Nanoparticles

The in situ exsolved nanoparticles from the perovskite matrix have achieved increasing attention and wide applications in solid oxide fuel cells (SOFCs) due to their excellent stability and high catalytic activity. Herein, an A-site-deficient (Ba0.9La0.1)0.95Co0.7Fe0.2Nb0.1O3 – δ (BL95CFN) perovskite oxide with in situ exsolved Co-Fe nanoparticles is developed and investigated as an anode for SOFCs. Compared with stoichiometric BLCFN, a tiny A-site deficiency (5%) promoted the exsolution of cobalt and iron from the perovskite matrix of BL95CFN. This hybrid anode catalyst showed excellent electrochemical performance. The polarization resistance is 0.11 Ω cm2 for the BL95CFN anode at 750 °C, about 42% lower than that of the BLCFN anode. The maximum peak density (MPD) reaches 513.2 mW cm–2 at 750 °C for an electrolyte-supported single cell with the BL95CFN anode. The high electrochemical performance could be attributed to the accelerated hydrogen surface exchange process provided by exsolved Co-Fe nanoparticles and oxygen ion transport in the A-site-deficient perovskite matrix. High-resolution transmission electron microscope (HRTEM) reveals that exsolved Co-Fe nanoparticles are embedded in the oxide matrix, forming a firm anchoring structure, which ensures excellent anode coking tolerance. At the current density of 200 mA cm–2, the output voltage of the single cell remained stable within 200 h in methane fuel. Overall, the high catalytic activity and coking tolerance of the hybrid electrocatalyst manifest a bright prospect of application in SOFCs and electrolytic cells.

The Physical Characterisation of Coating via Electrophoretic Deposition (EPD) with Voltage and Duration Variables for Solid Oxide Fuel Cell Application - A Review

This review covers the basics of electrophoretic deposition (EPD) techniques and its effect on the physical characterisation for solid oxide fuel cell (SOFC) application. SOFChave gotten a lot of attention in recent years as a future alternative energy generation technology because of their ability to utilise hydrocarbon fuels and high efficiency. On top of that, the characterisation of coating often affected by the variation of voltage (30V,50V,70Vand 100V). The higher the voltage (100V), the more deposition weight obtained. The thickness and morphology of the coating layer were determined by using Scanning Electron Microscopy (SEM).The duration of deposition (1.5 minutes to 3 minutes) also crucial as it can influence the thickness of the coating layer which in the range 11.90 μm to 29.30 μm. Therefore, this paper will benefit future works on SOFC application.

Numerical Investigations on the Damage Behaviour of a Reconstructed Anode for Solid Oxide Fuel Cell Application

This paper addresses the damage behaviour of a nickel/yttria-stabilised zirconia (Ni-YSZ) anode, in order to understand microstructural degradation processes of Solid Oxide Fuel Cells (SOFCs) during long-term operation. Numerical investigations are carried out to analyse the failure mechanisms in detail. For this purpose, finite element (FE) models are generated from focused ion beam-scanning electron microscopy 3D image data, representing the anode microstructure with varying phase compositions. A brittle model and a ductile material model were assigned to the YSZ phase and the nickel phase, respectively. The porosity is found to affect the strength of the microstructure significantly, leading to low compressive strength results. A high Ni content generally increases the toughness of the overall structure. However, the orientation and the geometry of the nickel phase is essential. When the Ni phase is aligned parallel to the loading direction, a supporting effect on the microstructure is observed, resulting in a significant high toughness. On the contrary, a rapid failure of the sample occurs when the Ni phase is oriented perpendicular to the loading direction. Two main failure mechanisms are identified: (i) cracking at the Ni/YSZ interface and (ii) cracking of struts at the location of the smallest diameter.

Influence of mixing time during glycine–nitrate process on the structural properties and reducibility of a dual-phase Ni–Cu–Mn spinel catalyst

The potential of Ni–Cu–Mn spinels as methane reforming catalysts for hydrocarbon-fueled solid oxide fuel cell (SOFC) applications is highly dependent on its catalytic properties, particularly reducibility. The reducibility of a spinel-structured catalyst is often correlated with its structural properties and fabrication processes. In this work, the structural properties and reducibility of a Ni–Cu–Mn spinel catalyst was evaluated on the basis of mixing time during the glycine–nitrate process. Phase analysis results showed that Ni 0.4 Cu 0.6 Mn 2.0 O 4 and (Cu, Mn) 3 O 4 in normal or inversed spinel structures were observed in GNP-produced Ni–Cu–Mn spinel catalyst powders. Distortion in inverse spinel structures enhanced the reducibility of the spinel catalyst. Morphological analysis results showed that complete nitrate binding occurred at a minimum mixing time of 24 h and resulted in homogenous particle size distribution and uniform elemental distribution. Furthermore, the Ni–Cu–Mn spinel catalyst produced after 24 h of mixing was fully reduced at 450 °C. The reducing pattern of the Ni–Cu–Mn spinel catalyst produced after 24 h of mixing time showed strong metal–support interaction and the fast adsorption of reactants. These effects were due to either the distribution of divalent cations in octahedral sites or large amounts of bulk pores. In conclusion, a minimum mixing time of 24 h is sufficient to produce the desired structural properties and reducibility of Ni–Cu–Mn spinel catalysts for SOFC applications.

Development of a Combined Plasma‐Matrix Reformer for Solid Oxide Fuel Cell Application

AbstractA novel plasma‐matrix reformer (PMR) was suggested for methane conversion into hydrogen‐rich fuel. To demonstrate the possibility of reforming performance, characteristics of product gas and CH4 conversion were identified according to O2/C ratio, water vapor supply, reformed gas recirculation, and water feed in the recirculation gas affecting energy conversion and hydrogen production. When the reformed gas recirculation and water feed to the recirculation pipe were performed at the same time, hydrogen production and energy conversion efficiency were superior compared to the conventional reforming method. The optimal operating conditions of the PMR were determined. The obtained high energy conversion efficiency and hydrogen selectivity indicated the applicability to solid oxide fuel cell stacks for residential power generation.

Behaviour of 54.4SiO2-13.7Na2O-1.7K2O-5.0CaO-12.4MgO-0.6Y2O3-11.3Al2O3-0.9B2O3 HT-SOFC glass sealant under oxidising and reducing atmospheres

The behaviour of the promising glass sealant 54.4SiO2-13.7Na2O-1.7K2O-5.0CaO-12.4MgO-0.6Y2O3-11.3Al2O3-0.9B2O3 for solid oxide fuel cells (SOFCs) under SOFC operating conditions was studied. First, the kinetics of the crystallisation processes at the operating temperature (850 °C) was discussed (maximum exposure time of 1000 h), and the effect of crystallisation on the coefficient of thermal expansion (CTE) of the sealant was studied. Furthermore, the degradation processes at the interface of the glass sealant and functional SOFC materials (Crofer 22 APU, YSZ, and NiO(Ni)-YSZ) during exposure to 850 °C in oxidising and reducing atmospheres for 500 h were studied. The tests demonstrated good performance of the sealant studied and possibility of its application in SOFCs.

Synthesis and Structural Study of a Novel La0.67Ca0.33Cr0.9Cu0.1O3-δ Anode for Syngas-Fuelled Solid Oxide Fuel Cell

Solid oxide fuel cell (SOFC) is an alternative energy generation device that converts chemical energy into electrical energy from the use of hydrogen or hydrogen-rich fuel. A light hydrocarbon, e.g. methane (CH4), is a hydrogen-rich fuel that can be used as an alternative fuel to hydrogen in SOFC application. Carbon-containing fuel is accessible from natural gas, biogas, biomass gasification, etc. Biomass gasification produces methane, hydrogen (H2), etc. as syngas products which could be integrated with SOFC. As anode is an outer layer of SOFC which exposes to fuel, the development of anode for carbon-containing fuel application is essential. Conventional Ni-containing anode is found to create carbon deposition which degrades the cell. The replacement of copper (Cu) to Ni has been studied to enhance the direct electrochemical oxidation of dry hydrocarbons which is free from carbon deposition. With the interest of Cu doping, a La-based anode has been doped with 10 % Cu at B-site of perovskite structure as La0.67Ca0.33Cr0.9Cu0.1O3-δ and studied the X-ray diffraction (XRD), scanning electron microscope (SEM) and energy dispersive X-ray (EDX) for future application in syngas-fuelled SOFC.

Electrochemical Performance of NiCo2O4 Spinel Cathodes for Intermediate Temperature Solid Oxide Fuel Cells

It is a great challenge to develop the highly efficient cathode material for solid oxide fuel cells (SOFCs) at intermediate temperature, while high electronic conductivity, good thermal and chemical compatibility, and superior electrochemical performance of the AB2O4‐type spinel is attractive electrode material. Herein, the NiCo2O4 spinel is developed using the glycine‐nitrate process (GNP) method as a cathode material for IT SOFCs. The characterization of the phase structure, microstructure, and electrochemical performance are done using X‐ray diffraction, scanning electronic microscopy, and electrochemical impedance spectroscopy. The results show that NiCo2O4 exhibited a single cubic structure and good chemical compatibility with a ((Sc2O3)0.1(CeO2)0.01(ZrO2)0.89) (ScCeSZ) electrolyte material at 900 °C for 10 h. Furthermore, a NiO–YSZ anode |NiO–YSZ, AFL | ScCeSZ |NiCo2O4 SOFC cell exhibits the maximum power density (MDP) of 0.73 and 1.04 W cm−2 at 750 and 800 °C, respectively. These results recommend the spinel‐structured NiCo2O4 is a potential cathode material for IT SOFC application.

Electronic properties of SmxSr1−xMnO3 for solid oxide fuel cell application — a first-principles study

Electronic properties of orthorhombic SSM ([Formula: see text] and monoclinic SSM ([Formula: see text] are investigated using the first-principles calculation. The half-metallic behavior that leads to the mixed ionic and electronic conductivity (MIEC) property is identified in orthorhombic SSM. In addition, the strong covalent bonding between [Formula: see text]-p and [Formula: see text]-s orbitals of orthorhombic SSM is identified from the PDOS plot. The strong covalent bonding enhances the [Formula: see text] molecular adsorption on Mn atom. On the other hand, monoclinic SSM shows the pure conducting behavior and there is no covalent bonding between Mn and O atoms. Thus, the results suggest that the half-metal Sm[Formula: see text]Sr[Formula: see text]MnO3 might be a suitable cathode material for intermediate-temperature solid oxide fuel cells.

Multi-physics field modeling of biomass gasification syngas fueled solid oxide fuel cell

In order to uncover the inner working mechanism and performance of solid oxide fuel cell (SOFC) with biomass gasification syngas as fuel, a two dimensional SOFC multi-physical field model is established. This study makes up for the deficiency that the previous studies of coupling biomass gasification unit and SOFC stack mostly stay at the system level. The results show that the SOFC fueled by the syngas produced from gasification of biomass with steam as the agent has the best performance. The peak power density could achieve approximately 10240 W m−2. With the improvement of operating temperature, the peak power density of SOFC will be increased. At the temperature of 1123 K, the peak power density could achieve about 15128 W m−2. The average reaction rate of water gas shift (WGS) reaction is −29.73 mol m−3 s−1 when the operating temperature is 1123 K. This indicates that the WGS reaction will proceed in reverse direction at high temperatures, thereby reducing the hydrogen concentration. In addition, increase in the anode flux and decrease in the cell length lead to the increase of SOFC current density. In general, this work could provide guidance for the optimization and practical application of SOFC using biomass syngas as fuel.

Effect of Oxygen Partial Pressure on Reactive-Sputtered Ni-YSZ Anode Properties for Low-Temperature Solid Oxide Fuel Cell

Solid oxide fuel cell (SOFC) is a promising next-generation energy conversion device because of its high efficiency, cleanliness, and fuel flexibility. Recently, SOFC operating at low- to intermediate-temperature (LT to IT) range (< 600 ℃) has been studied to overcome the limitations of conventional SOFC, e.g., thermal stability, cost, and limited application. In lowered temperature range, however, charge transfer and transport rates slow down; therefore, SOFCs design with thin film stacks, namely thin film SOFC (TF-SOFC) fabricated on porous anode support have been usually adopted for sufficient power density even at this temperature regime.TF-SOFC usually uses Ni-YSZ (nickel-yttria-stabilized zirconia) cermet for anode functional layer (AFL) to accommodate the deposition of dense electrolyte layers on anode support with relatively large pores because of its reasonable cost, catalytic activity, and electrical conductivity. While various thin film techniques have been reported for AFL fabrication, e.g., pulsed layer deposition (PLD), RF sputtering, etc. Among such techniques, reactive sputtering method, which uses metal target in controlled gas environment (e.g., oxygen environment for oxide deposition), is a versatile method to deposit various types of thin films with fast speed (up to > 1um/hr), which is beneficial in manufacturabilily regarding the usual thickness range of AFL (a few microns). Furthermore, the reactive co-sputtering method can control anode properties such as composition ratio, deposition speed, and morphology in wide ranges.In this study, we fabricate reactive sputtered Ni-YSZ cermet anodes, as prototypes for AFLs of TF-SOFCs, by using a single metal target with various oxygen partial pressure conditions, and characterize their physical and chemical properties. Oxygen partial pressure significantly affects deposition speed, surface morphology, composition, electrochemical performance and its thermal durability at 450 ℃. The Ni-YSZ anode sputtered at the environment of O2/Ar partial pressure ratio of 0.1 sample shows the lowest activation resistance when applied to LT-SOFC’s anode. It is also shown that excessive O2/Ar partial pressure ratio (> 0.2) significantly reduces the deposition speed by approximately one order of magnitude compare to the lower ratio case.

Techno-economic and Environmental Comparison of Internal Combustion Engines and Solid Oxide Fuel Cells for Ship Applications

In order to quantify the economic and environmental impact of technology selection in ship power systems, four different battery-supported hybrid configurations including diesel and gas combustion engines, as well as natural gas fueled solid oxide fuel cells (SOFCs) are modeled and analyzed. The investigations include component investments, maintenance and operational costs, as well as the components’ and fuels’ carbon footprints, operational greenhouse gases and other relevant emissions. Dynamic energy system models are used to derive economically optimal system designs for an appropriate technology comparison in a cruise ship case study. The assessment is conducted for a cruise ship case study with technology parameters for the near future and 2050. Results indicate that the auxiliary power system based on diesel combustion is inferior both economically and environmentally compared to SOFCs or gas combustion engines. While latter are the most cost efficient, SOFC application provides an environmental improvement without the need for a new fuel such as hydrogen. In a final outlook for the year 2050, SOFCs economically overtake gas combustion engines on the condition that their investment costs decrease and synthetic fuels are introduced to the market as a low emission solution.

Study on biochar as desulfurizer for SOFC application

AbstractThe potential of biogas as a source of H2 for the operation of solid oxide fuel cells (SOFC) has received much attention in recent years. However, in order to achieve commercial‐level stability of a biogas‐fueled SOFC system, impurities in biogas such as H2S, which poisons the reforming catalyst and anode material, must be eliminated. In this study, an environmentally‐friendly biogas purification process using biochar was explored. Bamboo (BB) and rice husk (RH) were chosen as starting materials and heat‐treated at 500°C for 120 min in an O2‐free atmosphere to produce BB‐ and RH‐derived biochars, BB‐BC and RH‐BC, respectively, then treated with steam or ammonia. H2S adsorption tests were performed for these biochar samples, and breakthrough capacity (ACPH2S(0)) and total H2S adsorption capacity (ACPH2S) were evaluated. Steam treatment effectively increased ACPH2S(0) and ACPH2S for BB‐BC, however, intense steam treatment had a negative effect, especially for RH‐BC because of the silica exposed on the surface. Ammonia treatment of biochar to form pyridinic N sites on the carbon surface was considerably effective to enhance the performance of a biochar as desulfurizer. By the ammonia treatment of RH‐BC at 900°C, ACPH2S(0) and ACPH2S increased by 2 and 30 times, respectively.

Electrical properties of praseodymium and samarium co-doped ceria electrolyte for low-temperature solid oxide fuel cell application

Electrical properties of praseodymium and samarium co-doped ceria electrolyte for low-temperature solid oxide fuel cell application

Development and application of lanthanum tungstate series proton conductors

<p indent=0mm>As one of the most important clean energy and commodity chemicals, hydrogen is widely used in human life and industrial production. In the present decade, three main technologies for hydrogen recovery have been developed, namely pressure swing adsorption (PSA), cryogenic separation, and membrane separation. Among these three different hydrogen recovery technologies, the membrane separation method is favored for its high efficiency. Benefiting from its absolute selectivity of hydrogen and the low cost, mixed protonic-electronic conductors (MPEC) have become an important research object in the field of hydrogen separation membrane materials, which enable a significant approach for the purification and utilization of hydrogen energy. For the traditional proton-conducting perovskite oxides doped with Ce and Zr, although they have high proton conductivity, their poor chemical stability under the atmosphere in the presence of CO₂ and H₂O hinders the commercial application. Rare-earth metal compound lanthanum tungstate material (LWO) is a kind of crucial proton conductor, which has good chemical stability in CO₂ atmosphere. However, the hydrogen permeability of LWO is not satisfactory because of the low electronic conductivity. A variety of effective methods to improve the hydrogen permeability of lanthanum tungstate film are summarized in this review. This review introduces the basic electronic conductivity of LWO-based single-phase materials, with the emphasis on improving the electronic conductivity of LWO by adjusting La/W ratio, cation doping strategies, and preparation methods. Furthermore, it reviews breakthroughs in their application in proton-conducting solid oxide fuel cells (SOFC) as well as hydrogen separation membranes. The problems now faced by LWO oxides are analyzed and their future development is predicted. Firstly, the proton conductivity of LWO is positively correlated with the La/W ratio. Adjusting the La/W ratio improves proton conductivity of LWO. For cation doping, the substitution of W rather than La more effectively improves the proton conductivity of LWO. Secondly, compositing LWO and the electronic conductors effectively enhance the performance of the hydrogen permeation membranes. Thirdly, in terms of the SOFC applications, an additional oxide layer between the LWO electrolyte layer and the electrode layer avoids the phase reaction on the interface, which prevents the chemical incompatibility between the LWO and electrode materials. Many studies show that the maximum utilization of LWO can be realized by optimizing crystal structure, phase composition, and the SOFC structure. In view of the problems existing in the research of LWO materials, future research can be focused on the following aspects: (1) Further exploring the electronic-ionic conducting pathway and catalytic mechanism of LWO series materials, and then optimizing the electrochemical properties under the guidance. (2) Developing the electrode materials with good catalytic performance and good chemical compatibility with LWO which is significant to the stable operation of SOFC. Also, it is necessary to improve the cell preparation process in which the unbeneficial interface reaction between the electrode and the LWO can be avoided. (3) For hydrogen permeation membrane, future research can be developed towards optimization with cation doping, surface engineering, and composite materials preparation.

Synthesis and characterization of ZnO/samarium-doped ceria nanocomposites for solid oxide fuel cell applications

Synthesis and characterization of ZnO/samarium-doped ceria nanocomposites for solid oxide fuel cell applications

Structural and thermophysical behaviour of barium zinc aluminoborosilicate glasses for potential application in SOFCs

Structure property relationships in two series of BaO-ZnO-La2O3-Al2O3-B2O3-SiO2 glasses have been investigated to assess their suitability for use as sealants in solid oxide fuel cell (SOFC) applications. Density, mechanical properties, thermal and electrical properties have been investigated as a function of composition. Raman and Fourier transfer infra-red spectroscopies were undertaken to obtain insights into the glass structure. The mechanical properties are generally relatively high but the thermal expansion coefficients are lower than ideal for SOFC sealants. Of the glasses studied 9.74BaO-6.39ZnO-15.84La2O3-5.04Al2O3-15.63B2O3-47.37SiO2 (mol%) has the most promising properties for SOFC sealing applications.

In-situ exsolution of Ni nanoparticles to achieve an active and stable solid oxide fuel cell anode catalyst on A-site deficient La0.4Sr0.4Ti0.94Ni0.06O3-δ

(La,Sr)TiO3 has been investigated as a promising anode material for solid oxide fuel cells (SOFCs) owing to its high electronic conductivity and superior phase stability. However, the low catalytic activity of (La,Sr)TiO3 materials is a major obstacle to the application of SOFCs. Exsolution has emerged as an effective strategy to overcome the low catalytic activity of (La,Sr)TiO3 materials. In this work, Ni-doped A-site-deficient La0.4Sr0.4TiO3-δ (LST) (i.e., La0.4Sr0.4Ti0.94Ni0.06O3-δ; LSTN) with in-situ exsolved Ni nanoparticles (NPs) was developed and the effects of exsolved Ni NPs on H2 oxidation was investigated. The doped Ni was exsolved and formed NPs on the LSTN surface under reducing conditions. Owing to the high catalytic activity of the exsolved Ni NPs, the SOFC with LSTN-Ce0.9Gd0.1O2-δ (GDC) yielded a maximum power density of 0.46 W cm−2 at 850°C, 91% higher than that of the cell with LST-GDC, as well as high long-term and redox stability. Furthermore, density functional theory calculations revealed that the adsorption and dissociation of H2 were more favorable for exsolved Ni NPs than for pure Ni owing to the more positively charged surface of the exsolved Ni NPs in the LSTN. These results demonstrated that exsolution is an effective method for improving the electrocatalytic activity of perovskite (La,Sr)TiO3 materials.

Jet Fuel Desulfurization for Portable Solid Oxide Fuel Cell Applications

Solid oxide fuel cells (SOFCs) are capable of utilizing energy-dense hydrocarbon fuels such as jet fuels for highly efficient power generation. Currently, a major challenge for using the jet fuel (e.g. JP8) in SOFC power systems is its sulfur content, which poisons the SOFC catalyst and anode. Sulfur contents in jet fuels could be as high as 3000 ppm although typical sulfur contents could be in the range from 550 and 750 ppm. The reduction of sulfur to <1 ppm is generally desired and required to ensure reliable SOFC operation. Various technologies have been developed to remove sulfur from jet fuel. However, most of these technologies are designed for large-scale desulfurization at industrial facilities or for stationary applications. Due to their complexity and substantial weight and size, these systems are not suitable for onboard integration with portable fuel cells. Therefore, our research aimed at developing a lightweight, compact desulfurization reactor for onboard applications. After several versions of improvements, including the use of selective laser sintering (SLS) 3D printing method, we have developed a miniature one-piece stainless-steel reactor which is capable of removing >99.5% sulfur in the jet fuel with the final sulfur concentrations close to a sub-ppm level. The reactor could be adapted to the desulfurization of other liquid hydrocarbon fuels such as gasoline and diesel. The reactor designs, desulfurizing materials, operation conditions and effectiveness of the technology will be discussed in this paper.

Electrical Properties of Novel La0. 2Sr0.7-xCaxTi0.95Fe0.05O3-δ Based Fuel Electrode for Solid Oxide Cell

As the fuel electrode is a central component of solid oxide fuel cell (SOFCs), evaluation of novel fuel electrode materials for SOFCs has become a favorite research subject. Perovskite structure offers an excellent framework for altering the chemical and physical properties of a material due to its ability to accommodate many different cations. In the present research novel La0.2Sr0.7-xCaxTi0.3Fe0.7O3-δ (LSCFT) fuel electrode compositions have been synthesized by glycine-nitrate reaction for high-temperature solid oxide fuel cell application. For analysis of the influence of Sr/Ca ratio on the electrical conductivities of different compositions of LSCFT, the DC four-probe conductivity measurement method has been performed. Conductivities have been measured at three different atmospheres: synthetic air; 97% H2 + 3% H2O and in 1%H2 + 3% H2O + 96% Ar. The crystal structure and microstructure have been studied using X-ray diffraction and SEM, respectively to confirm the purity of phase and percentage of porosity.In previous studies by Irvine et al. [1] has been demonstrated the effect of calcium doping on A-site deficient lanthanum strontium titanate, which displayed enhancement of its electrical conductivity and maximum conductivity was observed for La0.20Sr0.25Ca0.45TiO3 (LSCT) composition. Moreover, the same composition was tested and it confirmed as an active fuel electrode in fuel cell conditions, where good performance was achieved [2].Keywords: Fuel electrode, Electrical conductivity, Layered Perovskite, MIEC material, high temperature SOFC.[1] Aljaberi AD, Irvine JTS. Ca-substituted, A-site deficient perovskite La0.2Sr0.7TiO3 as a potential anode material for SOFCs. J Mater Chem A 1 (2013) 5868-74.[2] Verbraeken MC, Iwanschitz B, Mai A, Irvine JTS. Evaluation of Ca doped La0.2Sr0.7TiO3 as an alternative material for use in SOFC anodes. J Electrochem Soc 159 (2012) F757-62.