Micro solid oxide fuel cell fabricated on porous stainless steel: a new strategy for enhanced thermal cycling ability

Miniaturized solid oxide fuel cells (micro-SOFCs) are being extensively studied as a promising alternative to Li batteries for next generation portable power. A new micro-SOFC is designed and fabricated which shows enhanced thermal robustness by employing oxide-based thin-film electrode and porous stainless steel (STS) substrate. To deposit gas-tight thin-film electrolyte on STS, nano-porous composite oxide is proposed and applied as a new contact layer on STS. The micro-SOFC fabricated on composite oxide- STS dual layer substrate shows the peak power density of 560 mW cm−2 at 550 °C and maintains this power density during rapid thermal cycles. This cell may be suitable for portable electronic device that requires high power-density and fast thermal cycling.1111Ysciescopu

Sparked Reduced Graphene Oxide for Low-Temperature Sodium Beta Alumina Batteries

Wetting Na metal on the solid electrolyte of a liquid Na battery determines the operating temperature and performance of the battery. At low temperatures below 200 degrees C, liquid Na wets poorly on a solid electrolyte near its melting temperature (T-m = 98 degrees C), limiting its suitability for use in low-temperature batteries used for large-scale energy-storage systems. Herein, we propose the use of sparked reduced graphene oxide (rGO) that can improve the Na wetting in sodium-beta alumina batteries (NBBs), allowing operation at lower temperatures. Experimental and computational studies indicated rGO layers with nanogaps exhibited complete liquid Na wetting regardless of the surface energy between the liquid Na and the graphene oxide, which originated from the capillary force in the gap. Employing sparked rGO significantly enhanced the cell performance at 175 degrees C; the cell retained almost 100% Coulombic efficiency after the initial cycle, which is a substantial improvement over cells without sparked rGO. These results suggest that coating sparked rGO is a promising but simple strategy for the development of low-temperature NBBs. © 2019 American Chemical Society11sciescopu

Acceptor-doped ceria deposited on a porous Ni film as a possible micro-SOFC electrolyte

3 Micro-SOFCs, miniaturized solid oxide fuel cells (SOFCs) for low temperature operation, are being developed as a power source for portable electronics. Reducing the thickness of the electrolyte and the adoption of acceptor-doped ceria as an electrolyte material are important to minimize the Ohmic resistance at low temperature. Acceptor-doped ceria thin-films are often deposited on nano-porous metal substrates to reduce cracking of the thin electrolyte. However, due to the difficulty of depositing a pore-free electrolyte on a porous medium, the cells often show the low open circuit voltages (OCVs). In this study, we have deposited similar to 1 mu m-thick Gd-doped ceria on a nano-porous nickel film to assess whether a thin-film, metal-supported GDC can be deposited as a pore-free layer and would thus be suitable as an electrolyte of micro-SOFCs. The Ni-supported GDC cell showed an OCV of similar to 0.92 V at 450 A degrees C under a hydrogen/air gradient. The high OCV verifies that the thin-electrolyte layer, deposited on porous Ni using the pulsed laser deposition (PLD) method, is dense enough to prevent gas leakage as also observed in its microstructure.X1132sciescopu

Electrical conductivity of Gd-doped ceria film at low temperatures (300-500 degrees C)

Gd-doped ceria (GDC, Ce1 - xGdxO 2 - δ, x = 0.14-0.16) thin-films were deposited on sapphire substrate by RF-magnetron sputtering and their electrical conductivities of films were measured as a function of temperature (T = 300-500 °C) and oxygen partial pressure (Po2). All films showed columnar grains with crystallite size of 18-36 nm. The films annealed at high temperature and deposited from dense target exhibited their ionic conductivities similar to or higher than bulk GDC. The electronic conductivities of GDC films shown in low Po2 range, however, were higher than that of bulk GDC.X119Nsciescopu

Effect of Al- or Ga-additive on ionic conductivity of thin-film Gd-doped ceria

For acceptor-doped ceria, thin films have usually shown lower ionic conductivity compared to the bulk. In this communication, the effect of additives (1 mol% of Ga2O3 or Al2O3) has been studied in terms of the film quality and the magnitude of the ionic conductivity of Gd-doped ceria (GDC). With additives, the films show strong (111)-orientation and the increased magnitude of ionic conductivity. The GDC film with the addition of 1 mol% Ga2O3 shows the highest conductivity among films and the conductivity is comparable to that of bulk samples. This proves that Ga and Al additives are useful to densify the film and that they reduce the grain-boundary resistivity of the thin films of acceptor-doped ceria. (C) 2013 Elsevier B.V. All rights reserved.X1122sciescopu

Micro-solid oxide fuel cell supported on a porous metallic Ni/stainless-steel bi-layer

Metallic bi-layer of porous Ni and porous stainless steel (STS) is utilized as a support for micro-solid oxide fuel cells (SOFCs) using a thin-film layer of electrolyte. Tape-casting and screen-printing processes are employed to fabricate a thick (similar to 250 mu m) STS-layer covered with a thin (similar to 20 mu m) nano-porous Ni layer. Successful deposition of a nearly pore-free electrolyte layer by the pulsed laser deposition (PLO) method is demonstrated by the high open-circuit-voltage (OCV) value of a single cell. The Ohmic resistance of the micro-SOFC deposited on a porous Ni/STS-support is stable and it shows similar to 28 mW cm(-2) after operation for similar to 112 h at 450 degrees C. The use of a porous Ni/STS bi-layer as a support for micro-SOFCs is successfully demonstrated. (C) 2013 Elsevier B.V. All rights reserved.X1198sciescopu

A Hierarchically Ordered Mesoporous-Carbon-Supported Iron Sulfide Anode for High-Rate Na-Ion Storage

Sodium-ion batteries (SIBs) are promising alternatives to lithium-based energy storage devices for large-scale applications, but conventional lithium-ion battery anode materials do not provide adequate reversible Na-ion storage. In contrast, conversion-based transition metal sulfides have high theoretical capacities and are suitable anode materials for SIBs. Iron sulfide (FeS) is environmentally benign and inexpensive but suffers from low conductivity and sluggish Na-ion diffusion kinetics. In addition, significant volume changes during the sodiation of FeS destroy the electrode structure and shorten the cycle life. Herein, we report the rational design of the FeS/carbon composite, specifically FeS encapsulated within a hierarchically ordered mesoporous carbon prepared via nanocasting using a SBA-15 template with stable cycle life. We evaluated the Na-ion storage properties and found that the parallel 2D mesoporous channels in the resultant FeS/carbon composite enhanced the conductivity, buffered the volume changes, and prevented unwanted side reactions. Further, high-rate Na-ion storage (363.4 mAh g−1 after 500 cycles at 2 A g−1, 132.5 mAh g−1 at 20 A g−1) was achieved, better than that of the bare FeS electrode, indicating the benefit of structural confinement for rapid ion transfer, and demonstrating the excellent electrochemical performance of this anode material at high rates

Characteristics of the Discoloration Switching Phenomenon of 4H-SiC Single Crystals Grown by PVT Method Using ToF-SIMS and Micro-Raman Analysis

The discoloration switching appearing in the initial and final growth stages of 4H-silicon carbide (4H-SiC) single crystals grown using the physical vapor transport (PVT) technique was investigated. This phenomenon was studied, investigating the correlation with linear-type micro-pipe defects on the surface of 4H-SiC single crystals. Based on the experimental results obtained using time-of-flight secondary ion mass spectrometry (ToF-SIMS) and micro-Raman analysis, it was deduced that the orientation of the 4H-SiC c-axis causes an axial change that correlates with low levels of carbon. In addition, it was confirmed that the incorporation of additional elements and the concentrations of these doped impurity elements were the main causes of discoloration and changes in growth orientation. Overall, this work provides guidelines for evaluating the discoloration switching in 4H-SiC single crystals and contributes to a greater understanding of this phenomenon