• Energy Research

Abstract Solid-oxide fuel cells (SOFCs) are the most widely used fuel cells because they exhibit flexibility, power generation efficiency, and low pollution formation. Research on SOFC anodes is a major and challenging task in the field of SOFCs. This review highlights the anode materials that may be used for SOFC applications. The use of cermet-based oxide materials as anodes for SOFCs is also discussed in detail. A literature survey conducted over the last 10 years shows that increased power generation efficiency may be attributed to anode materials used in such cells. Oxide-based anode materials with perovskite and several oxides with cubic fluorite structures are further described. Based on the review conducted, we find that cubic fluorite-structured compounds are the most promising anode materials reported thus far. Analyses of the structure and electrical performance of anode materials show as well that copper–gadolinium-doped cerium oxide (Cu–GDC) cubic fluorite-structured anodes exhibit higher electronic conductivity potential than yttria-stabilized zirconia-based anode materials.

Despite being the most efficient and quiet operation type of fuel cells, solid oxide fuel cells (SOFCs) deal with several constraints in terms of fabrication cost, material selection and durability issues due to their high operating temperature. The high operating temperature of SOFCs limits their stationary and large-scale applications. Moreover, these constraints restrict the commercialization of portable SOFCs. Therefore, the operation temperature of SOFCs must be reduced to overcome the aforementioned problems. However, this task is challenging because the operation temperature mainly affects the material preparation and the stack design to produce the electrical power needed for small-scale applications. This paper provides an overview of the challenges faced by each component such as the materials, the design of stack, fabrication cost and related research in fabricating high power SOFC stacks.

In this study, the effects of different fabrication techniques on the electrochemical performance of solgel derived La0.6Sr0.4CoO3-? (LSC) cathode material for intermediate temperature proton-conducting fuel cells were investigated. Single-phase, sub-micron LSC powder was used to prepare cathode slurries by a simple grinding-stirring (G-S) technique and an advanced ball milling-triple roll milling (BM-TRM) technique. The prepared G-S and BM-TRM cathode slurries were brush painted and screen printed, respectively, onto separate BaCe0.54Zr0.36Y0.1O2.95 (BCZY) proton-conducting electrolytes to fabricate symmetrical cells of LSC|BCZY|LSC. The thickness of LSC cathode layer prepared by brush painting and screen printing was 17 ? 0.5 ?m and 7 ? 0.5 ?m, and the surface porosity of the layers was 32% and 27%, respectively. Electrochemical impedance spectroscopy analysis revealed that the layer deposited by screen printing had lower area specific resistance measured at 700?C (0.25Wcm2) than the layer prepared by brush painting of G-S slurry (1.50Wcm2). The enhanced LSC cathode performance of the cell fabricated using BM-TRM assisted with screen printing is attributed to the improved particle homogeneity and network in the prepared slurry and the enhanced particle connectivity in the screen printed film.

Abstract Hydrogen is considered a fuel of the future due to its diversified supply and zero greenhouse gas emission. The application of advanced membrane technology for hydrogen separation within the larger hydrogen production process context can substitute the use of more expensive and energy intensive cryogenic distillation and pressure swing adsorption technologies. This review overviews the basic aspects and progresses in perovskite-based proton conducting hydrogen separation membranes. Different configurations such as symmetric, asymmetric, hollow fiber, and surface modified perovskite membranes with various compositions are discussed and summarized. The challenges and future directions of such membranes are also elaborated.

Abstract Most technologies for fabricating solid oxide fuel cells (SOFCs) are adopted from ceramic-fabrication methods. Selecting an appropriate method of preparing SOFC components is a main concern for many researchers because the method can strongly affect SOFC properties and performance. The method must be reproducible and highly controllable to improve SOFC performance and durability. SOFC fabrication methods have been customized to achieve high power outputs at low operation temperatures and thus broaden the choice of material and reduce fabrication cost. This article provides an overview of planar SOFC fabrication methods. Planar SOFC fabrication methods such as uniaxial pressing, tape casting, screen printing, dip coating, and slurry spin coating are discussed because these methods are cost effective. This article also discusses the technical parameters that can influence the processes of these methods and SOFC performance. The methods of preparing the materials of SOFC components are discussed because these methods directly affect the fabrication process.

Performance tests are vital for the development of solid-oxide fuel cells (SOFCs) and can help determine the potential of developed SOFCs. However, the challenges in performing these tests such as cost, time, and safety limit the development of SOFCs. Computational fluid dynamics (CFD) can be used to numerically predict the performance of developed SOFCs. CFD methods enable the exploration of many design and operational parameters that are difficult to assess experimentally. This paper focuses on the assumptions and boundary conditions used to model the SOFC stack by using a CFD method. Through the discussions, we briefly explain several assumptions that are commonly found in SOFC modeling. These assumptions are important because they can influence the modeling processes and parameters required for simulations. The boundary conditions required for SOFC modeling are then described to provide an overview on how SOFC operations are incorporated into the model and simulations. Our results can help elucidate the significance of assumptions and boundary conditions used in the CFD modeling of SOFCs

The (Cu,Mn,Co)3O4 (CMC) spinel layer is useful in inhibiting Cr vaporization that deteriorates the solid oxide fuel cell performance. The effectiveness of the spinel layer in suppressing volatile Cr species from the metallic interconnects is strongly dependent on layer density, which is influenced by particle size distributions and agglomerations of the spinel powders. Considering that the material properties were influenced by the synthesizing conditions, this study elucidated the influences of citric acid (fuel) on the structure, morphology, and electrical properties of sol–gel derived CMC spinel powders. Dual-phase CMC spinel powders, consisting of cubic CuMnCoO and tetragonal Mn2CoO4, were successfully synthesized at citrate-to-nitrate (CA/MN) ratios of 0.8, 1.0, and 1.2. An undesired CuCo2O4 phase was observed in spinel powders synthesized at a low CA/MN ratio of 0.5. The CA/MN ratio has influenced not only the phase formation of CMC spinel, but also the particle size distributions. The CA/MN ratio of 1.0 yielded the finest CMC spinel with the least agglomerates, which then produced the highest electrical conductivity of 116 Scm−1. Therefore, the CA/MN ratio of 1.0 was recommended for the synthesis of CMC spinel, which can be used in fabricating the protective coating of solid oxide fuel cell interconnects.

Abstract Fabrication of solid oxide fuel cell (SOFC) components via a simple and economical technique is critical to lower the overall manufacturing cost of SOFCs. Thus, screen-printing is widely used to fabricate SOFC components having thickness in the range of 10–100 µm. Fabrication of optimized screen-printing inks is highly significant for the production of high quality films with improved performance. The effect of solid, binder, solvent and dispersant on the ink rheological properties and performance of resultant films must be deeply understood for the fabrication of optimized screen-printing inks. These effects can be optimized by measuring the rheological properties of inks such as viscosity, yield stress, thixotropy and viscoelasticity for application at a specific printer setting. Understanding the relationship between the composition and rheology of the inks may enhance the properties and performance of the resultant screen-printed films. Furthermore, these parameters can be correlated to the film properties such as mechanical strength, electrical conductivity and electrochemical properties of the resultant films. The focus of this review paper is to understand the underpinning science of ink rheology and processing conditions of screen-printing inks for the fabrication of high performance SOFC electrodes and/or electrolyte.

Abstract Immobilized cell technology is a new technique to produce biogas. In the present study, an immobilized mixed-culture reactor (IMcR) in batch-mode operation was used for the production of hydrogen and methane simultaneously from glucose. Several factors, such as glucose concentration, temperature and fermentation time, were evaluated to determine the optimal conditions for hydrogen and methane production. Gas chromatography with a thermal conductivity detector (GC-TCD) and high-performance liquid chromatography (HPLC) were used to analyse the gas and effluent. The morphologies of the immobilized cells were characterized using scanning electron microscopy (SEM). The optimal conditions for hydrogen and methane production were obtained using a substrate with 5.0 g/L glucose at 60 °C for fermentation times of 48.0 h (hydrogen) and 72.0 h (methane). The maximum yields of hydrogen and methane at these optimal conditions were 37.0 ± 0.0 (×10 −3 ) mol/mol glu and 39.0 ± 0.0 (×10 −3 ) mol/mol glu, respectively. The chemical oxygen demand ( COD ) and pH gradually decreased with increasing fermentation time and temperature. However, the performance of the IMcR decreased over time due to cell damage and microorganism detachment from the cell. In conclusion, the IMcR system is a potential system for the simultaneous production of hydrogen and methane.