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Ammonia is known as an alternative hydrogen supplier because of its high hydrogen content and convenient storage and transport. Hydrogen production from ammonia decomposition also provides a source of hydrogen for fuel cells. While catalysts composed of ruthenium metal atop various support materials have proven to be effective for ammonia decomposition, non-precious-metal-based catalysts are attracting more attention due to desires to reduce costs. We prepared a series of Fe, Co, Ni, Mn, and Cu monometallic catalysts and their alloys as catalysts over proton-conducting ceramics via the impregnation method as precious-metal-free ammonia decomposition catalysts. While Co and Ni showed superior performance compared to Fe, Mn, and Cu on a BaZr0.1Ce0.7Y0.1Yb0.1O3−б (BZCYYb) support as an ammonia decomposition catalyst, the cost of Fe is much lower than that of other metals. Alloying Fe with Co can significantly increase the conversion and stability and lower the overall cost of materials. The measured ammonia decomposition rate of FeCo/BZCYYb reached 100% at 600 °C, and the ammonia decomposition rate was almost unchanged during the long-term test of 200 h, which reveals its good catalytic activity for ammonia decomposition and thermal stability. When the metallic catalyst remained unchanged, BZCYYb also exhibited better performance compared to other commonly used oxide supports. Finally, when ammonia cracked using our alloy catalyst was fed to solid oxide fuel cells (SOFCs), the peak power densities were very close to that achieved with a simulated fully cracked gas stream, i.e., 75% H2 + 25% N2, thus proving the effectiveness of this new type of ammonia decomposition catalyst. [ABSTRACT FROM AUTHOR]

Underground coal gasification (UCG) technology can directly convert coal resources to syngas underground, making it important for coal utilization. In this work, the power generation, CO 2 electrolysis, and reversible operation of flat-tube solid oxide cells (SOCs) fueled with UCG syngas were studied. The factors affecting the performances of flat-tube solid oxide cells were investigated. Fueled with syngas (Swan Hills, Canada) at 750 °C, the flat-tube cell achieved a maximum power density of 329.4 mW cm−2 and a current density of 650.8 mA cm−2 at 1.4 V. 100-cycle (250 h) reversible operation of flat-tube SOCs running on syngas (Swan Hills) was accomplished. No carbon deposition on the surfaces of the cell fuel channels was detected. The syngas conversion in flat-tube cells was illuminated based on density functional theory calculations. • The performance of solid oxide cells (SOCs) with syngas was studied. • 100-cycle reversible operation of SOCs with UCG syngas was achieved. • No coking was detected after the long-term reversible test. • DFT calculations illustrated the reaction mechanisms of UCG syngas in SOCs. [ABSTRACT FROM AUTHOR]

One critical factor contributing to the performance degradation of solid oxide fuel cells (SOFCs) is the Ni migration in the anode. In this work, we studied and compared the influence of H 2 O and CO 2 concentrations in the fuel gas on Ni migration using patterned anode button cells. Scanning electron microscopy (SEM) images revealed the Ni migration emerged after 24 h of constant current discharge in fuel atmospheres containing H 2 O and CO 2. As the H 2 O content in the fuel increased, the rate of Ni migration increased, indicating that H 2 O promoted Ni migration at the anode side and contributed to the performance degradation. CO 2 improved Ni migration, and the effects of H 2 O and CO 2 on Ni migration were equivalent. Moreover, the mechanism of SOFC anode Ni migration induced by CO 2 in the fuel was discussed. • Ni migration in SOFC was observed by a specially designed patterned Ni-film anode. • Ni migration was significant at the pattern edge after constant current operation. • H 2 O and CO 2 in the fuel promoted Ni migration. • The effects of the same ratios of H 2 O and CO 2 on Ni migration were equivalent. [ABSTRACT FROM AUTHOR]

On-site hydrogen generation from ammonia decomposition is a promising technology to address the challenges of direct transportation and storage of hydrogen. The main problems with the existing support materials for ammonia decomposition catalysts are their high cost and time-consuming preparation process. In this work, ammonia decomposition catalysts consisting of in situ-formed nano-Ru particles supported on a naturally abundant mineral fiber, attapulgite (ATP), were proposed and studied. Also, 1 wt.% Ru was uniformly dispersed and anchored onto the surface of ATP fibers via the chemical method. We found that the calcination temperatures of the ATP support before the deposition of Ru resulted in little difference in catalytic performance, while the calcination temperatures of the 1Ru/ATP precursor were found to significantly influence the catalytic performance. The prepared 1 wt.% Ru/ATP catalyst (1Ru/ATP) without calcination achieved an ammonia conversion efficiency of 51% at 500 °C and nearly 100% at 600 °C, with the flow rate of NH3 being 10 sccm (standard cubic centimeter per minute). A 150 h continuous test at 600 °C showed that the 1Ru/ATP catalyst exhibited good stability with a degradation rate of about 0.01% h−1. The 1Ru/ATP catalyst was integrated with proton ceramic fuel cells (PCFCs). We reported that PCFCs at 650 °C offered 433 mW cm−2 under H2 fuel and 398 mW cm−2 under cracked NH3 fuel. The overall results suggest low-level Ru-loaded ATP could be an attractive, low-cost, and efficient ammonia decomposition catalyst for hydrogen production. [ABSTRACT FROM AUTHOR]

The oxidation of metal interconnects on the anode side in solid oxide fuel cells (SOFCs) leads to the degradation of the electrical properties, which affects the performance and long-term durability of SOFC stacks. In this study, we explored the oxidation behaviors of the SUS430 alloy interconnect in methanol-water anode atmosphere and investigated the possibility of using Sr 2 Fe 1.5 Mo 0.5 O 6-δ (SFM) perovskite materials as an oxidation-resistant coating on the anode side of the SUS430 alloy interconnect. The bare SUS430 alloy and the SUS430 alloy with SFM coating (thickness: ≈40 μm) were exposed in methanol/H 2 O anode atmosphere at 750 °C for 1000 h. After oxidation, a dense oxide scale with a thickness of 3.50 μm was formed on the surface of the bare SUS430 alloy; the area-specific resistance (ASR) of the alloy increased from 1.70 mΩ cm2 to 279.00 mΩ cm2. By contrast, the thickness of the oxide scale on the surface of SUS430 alloy with protective SFM coating under the same working condition was 0.70 μm; the ASR grows from 12.47 mΩ cm2 to 14.51 mΩ cm2. These results suggest that SFM forms an effective anode-side protective coating on the interconnects of SOFC stacks. • SUS430 alloy interconnect was protected by Sr 2 Fe 1.5 Mo 0.5 O 6-δ (SFM) coating. • Oxidation behaviors of bare and SFM-coated SUS430 alloy were analyzed in MeOH/H 2 O atmosphere. • SFM coating effectively inhibited oxidation behaviors of SUS430 alloy in MeOH/H 2 O atmosphere. • The area specific resistance of SFM-coated SUS430 alloy was stable during 1000 h operation. [ABSTRACT FROM AUTHOR]

Conversion of renewable energy sources like bioethanol to electricity using solid oxide fuel cells (SOFCs) is promising to reduce the consumption of fossil fuels and to mitigate global warming. However, direct ethanol-fed SOFCs are susceptible to carbon deposition on Ni-based anode. In this study, the power generation from and degradation mechanism of large-scale flat-tube SOFCs by direct internal reforming of ethanol are investigated. The steam/carbon (S/C) ratio causes minor influence on the cell performance but considerably affects the long-term durability. Elevating temperature improves ethanol conversion rate and cell performance. Ethanol is efficiently reformed by the thick anode support and long anode channels, with low selectivity for CH 4 and C 2 H 4. Stable power generation with current density of 200 mA/cm2 is obtained over 300 h under S/C = 2 and 3 at 800 °C. Due to the high operating temperature and complex cell structure, the in-situ measurements of the temperature and gas compositions within the cell, related to carbon deposition, are difficult. The distributions of the gas compositions and temperature within the cell before and after the durability test are clarified by simulation. Simulation results reveal that, in addition to CH 4 and C 2 H 4 , the cold zone near inlet contributes to carbon formation. • Power generation of large-scale direct ethanol-fed flat-tube SOFCs were studied. • Over 300 h stable operation was achieved under S/C = 2 and 3 at 800 °C. • The coking distribution and fields of temperature and composition were clarified. • The performance degradation was derived from coking and Ni agglomeration. • The decrease of local temperature near the inlet aggravated the carbon deposition. [ABSTRACT FROM AUTHOR]

The corrosion of ammonia atmosphere to Ni-cermet anode significantly affects the performance and durability of direct ammonia fuel solid oxide fuel cells. In this study, we investigate the impedance behavior of the flat-tube solid oxide fuel cells (SOFCs) fed with pure ammonia in details, assisted with distributions of relaxation time analysis under different fuels, operating temperatures, flow rates, and cell voltages. In addition, we use Ni/Al 2 O 3 particles and nickel foam strips as the built-in catalysts to enhance ammonia decomposition within the anode support of the flat-tube cells. It is confirmed that the increased catalytic activity of ammonia decomposition brought by the built-in catalyst and the change of internal fuel gas resistance would affect the initial performance of the cell. In addition, enhancing the catalytic activity of ammonia decomposition through the built-in catalyst could effectively inhibit the corrosion effect of ammonia on the Ni surface in the anode support, thus enhancing the long-term durability of ammonia-fueled SOFC. • Power generation from flat-tube solid oxide fuel cells (SOFCs) fed with ammonia. • Factors affecting the cell performance of NH 3 -fed SOFCs was investigated. • Impedance behavior of the NH 3 -fed SOFCs was clarified by DRT analysis. • Built-in catalyst significantly improved the durability of direct NH 3 -fed SOFC. [ABSTRACT FROM AUTHOR]

Co-electrolysis of H 2 O and CO 2 by high-temperature solid oxide electrolysis cells (SOECs) is a useful approach for energy storage and carbon dioxide reduction. In this study, we conducted H 2 O/CO 2 co-electrolysis using a flat-tube SOEC and studied its electrochemical performance and durability. It was found that the increase of temperature and water fraction in fuel gas promote electrochemical performance. In addition, the co-electrolysis was found to be stable with a constant current density of 300 mA cm−2 for over 1000 h at 750 °C. The contribution of each electrode process to polarization resistance is elucidated by electrochemical impedance spectroscopy and distribution of relaxation time (DRT) analysis. The fuel electrode was found to degrade more significantly against duration time as compared to the oxygen electrode. Post-mortem analysis of the microstructure revealed the loss and sintering of Ni particles in active cathode functional layer at the inlet of the fuel electrode. Based on these results, the degradation mechanism of H 2 O/CO 2 co-electrolysis by the flat-tube SOEC was discussed in details. • H 2 O/CO 2 co-electrolysis was successfully conducted by using a flat-tube (FT) SOEC. • Performance of the FT cell for co-electrolysis was studied by EIS and DRT methods. • 1000 h of co-electrolysis has been carried under a current density of 300 mA cm−2. • The loss and agglomeration of Ni are the important causes of cathode degradation. [ABSTRACT FROM AUTHOR]

Direct internal reforming of methanol is applied as fuel for a Ni-YSZ anode-supported solid oxide fuel cell with a flat tube based on double-sided cathodes. It achieves a power density (PD) of 0.25 W/cm2 at 0.8 V, reaching about 90% of that is fueled by H 2. And the cell has been operated for more than 120 h by the direct internal reforming of methanol. The durability and apparent advantage for using humidified methanol may lead to widespread applications by direct internal reforming method for this new designed SOFC in the future. • Direct internal reforming of methanol was applied in the DSC SOFC. • Humidified methanol achieved a power density of 90% of that of H 2. • Stable operation for more than 120 h was reached by MeOH/H 2 O with DIR. [ABSTRACT FROM AUTHOR]

BaCe 0.7 Zr 0.1 Y 0.1 Yb 0.1 O 3-δ (BCZYYb) is one of the most popular electrolyte materials in proton ceramic fuel cells (PCFCs). The synthesizing method and properties of BCZYYb powders have a significant impact on the sintering activity of electrolyte materials. In this work, the BCZYYb electrolyte was synthesized by ammonium bicarbonate co-precipitation method (CPT), and was compared with the powder produced by solid-state reaction (SSR) and sol-gel (SG) methods. XRD results show the BCZYYb powder synthesized by the CPT method belongs to orthorhombic crystal system with a space group of Pmcn (No. 62) and the refined lattice parameters are a = 8.774 Å, b = 6.173 Å, and c = 6.203 Å. In humid air atmosphere, the total conductivity at 650 °C and the activation energy for the BCZYYb powder prepared via the CPT method was 2.1 × 10−2 S cm−1 and 0.46 eV, respectively, as compared with 1.9 × 10−2 S cm−1 and 0.45 eV for the SSR method, and 1.8 × 10−2 S cm−1 and 0.44 eV for the SG method. Under similar testing conditions, the measured peak power densities were 0.51, 0.35, and 0.40 W cm−2 at 650 °C for the anode supported PCFCs using electrolyte powder prepared via CPT, SSR and SG methods, respectively, which proves the CPT method is an effective and viable route for PCFCs applications. • BCZYYb powders are successfully prepared by CPT, SG, and SSR methods. • The CPT method shows better conductivity and performance than the other methods under similar testing conditions. • A 600-h test showed the cell with electrolyte prepared by the CPT method has a good long-term stability. [ABSTRACT FROM AUTHOR]

The state-of-the-art Ni/yttria-stabilized zirconia (YSZ) anodes in direct methanol solid oxide fuel cells (SOFCs) are vulnerable to carbon deposition. We propose two strategies to enhance coking tolerance of the cell, focusing on promoting the oxygen storage capacity of the Ni/YSZ anode and the methanol conversion in flat-tube SOFCs with an active area of 60 cm2. The Ni/YSZ anodes are decorated with nanosized gadolinia-doped ceria (GDC) by wet impregnation method and the fuel channels are filled with extra GDC-Ni/YSZ catalyst. Through these measures, carbon deposition in the modified cells is mitigated, and therefore the steam/carbon (S/C) ratio for successful long-term cell operation is significantly lowered, and the cell durability is improved. A GDC-Ni/YSZ cell with extra catalyst is operated for over 1200 h directly on methanol under low S/C ratios at 750 °C and carbon deposition is considerably suppressed. In addition, the degradation mechanism of the cell directly fueled with nearly-dry methanol (S/C = 0.1) is investigated. This work provides insight into efficient and durable SOFCs using biofuels, towards renewable energy conversion in large-scale commercial applications. • Power generation from flat-tube SOFCs on nearly-dry methanol was studied. • An efficient wet impregnation method suitable for flat-tube SOFC was developed. • The coking tolerance of the anode decorated with Gd-doped ceria was improved. • Extra catalyst in fuel channels enhanced methanol conversion and coking tolerance. • Over 1200 h operation was attained under low steam/carbon (S/C) ratios at 750 °C. [ABSTRACT FROM AUTHOR]

In this study, electrolysis of seawater in flat-tube nickel-yttria-stabilized zirconia (Ni-YSZ) electrode-supported solid oxide electrolysis cells (SOECs) were modeled and the effects of variations in electrical conductivity and microstructure of Ni-YSZ electrode support were investigated. When the current density was greater than 700 mA·cm−2, the conductivity of the electrode support decreased slightly with an increase in current density at 800 °C in hydrogen reduction environment; the conductivity of the electrode support decreased with an increase in the current density when the current density was greater than 400 mA·cm−2 at 800 °C in the seawater electrolysis environment. During long-term durability experiment of seawater electrolysis, the degradation rates in area specific resistance (ASR) were 0.096 mΩ·cm2/100 h and 0.207 mΩ·cm2/100 h with a current density of 300 mA·cm−2 (i.e., ≤400 mA·cm−2) and 1000 mA·cm−2 (i.e., ≥400 mA·cm−2), respectively. Besides, the various ions commonly present in seawater did not contaminate the Ni-YSZ support during the long-term durability test. The degradation mechanism of seawater electrolysis in flat-tube SOECs is discussed and clarified. • Conductivity of Ni-YSZ support in seawater environment is quantitatively studied. • Conductivity of Ni-YSZ support first increases and then decreases with electrolysis current. • ASR of Ni-YSZ support increases by 0.207 mΩ·cm2/100 h under 1000 mA·cm−2. • Conductivity of Ni-YSZ support is mainly related to Ni element, but not to seawater ions. [ABSTRACT FROM AUTHOR]

A simulated coke oven gas (COG) is used as internally-reformed (IR) fuel in an anode of solid oxide fuel cell based on double-sided cathodes (DSC-SOFC) and the durability of the cell is studied. The DSC-SOFC operates stably for over 240 h when the steam to methane (H 2 O/CH 4) ratio is above 3 with performance degradation of about 0.01% per hour, but it has a larger degradation of about 0.08% per hour when the H 2 O/CH 4 ratio is lower than 2.5. The mechanism of the cell degradation has been analyzed in detail. It is found that the H 2 O/CH 4 ratio approximately equal to 1 is the key point affecting cell performance. The results of cell analysis by energy dispersive spectroscopy and Raman spectroscopy indicate that carbon deposition mainly takes place at the inlet and at the middle of DSC-SOFC. Due to thick anode substrate in this type of cell, carbon distribution on the cross-section reveals that there are two carbon producing areas, one close to the anode surface, and the other near the three-phase boundary. Some of the deposited carbon can be carried by the fuel gas to exhaust which lowers the actual carbon amount in the cell, thus prolonging the cell operation. • DSC-SOFC realizes stable operation with more than 200 h by DIR COG as fuel. • H 2 O/CH 4 ratio approximately equal to 1 is the key point affecting cell performance. • Carbon deposition mainly takes place at the inlet and the middle of DSC-SOFC. • Carbon is mainly produced on the anode surface and at the three-phase boundary. • Deposited carbon in the cell can be carried out by the fuel gas to exhaust. [ABSTRACT FROM AUTHOR]

Proton ceramic fuel cell (PCFC) as a new generation of solid oxide fuel cells (SOFCs) has been an attractive and highly active research topic for directly converting chemical energy into electricity at intermediate to low temperatures. In this work, we co-tape cast anode support layer (ASL), anode functional layer (AFL) and electrolyte layer (EL) followed by co-sintering of the three layers at the same time. The peak power density (PPD) reaches to 1.06 W cm−2 at 650 °C and 0.6 W cm−2 at 600 °C under humidified H 2 and static ambient air, which is comparable to previously reported high-performance die-pressed cells. After about 100 h' initial activation and stabilization process, the cell shows no sign of degradation (actually a slight increase in performance of 4 % kh−1) for remaining 500 h' continuous test which is among one of the best stability test results in PCFC particularly via tape casting process, making the co-tape casting a very promising and attractive process for large-scale PCFC fabrication. • PCFCs are successfully prepared by co-tape casting of all layers. • The fabricated cell shows a peak powder density of about 1.06 W cm−2 at 650 °C. • A 600-h test showed the tested cell has a good long-term stability. [ABSTRACT FROM AUTHOR]

The performance stability of solid oxide fuel cells (SOFCs) under thermal and redox cycles is vital for large-scale applications. In this work, we investigated the effects of thermal and redox cycles on cell performances of flat-tube Ni/yttria-stabilized zirconia (Ni/YSZ) anode-supported SOFCs. Cell performance was considerably affected by the duration of oxidation during redox cycles and the heating rate during the thermal cycles. The cell tolerated 20 short-term redox cycles (5 min oxidation) without significant performance degradation. Besides, the cell exhibited superior stability during 8 thermal cycles with a slow heating rate (4 °C min−1) to that with a fast heating rate (8 °C min−1). These results reflected that the thick anode support (2.7 mm) offered strong resistance to the shocks caused by redox and thermal cycling. Moreover, the morphological changes of the Ni phase during the redox and thermal cycling were investigated using Ni-film anode cells. Agglomeration of Ni particles and dissociation between the Ni film and the YSZ substrate were confirmed after 5 redox cycles, whereas no significant changes in Ni film emerged after 8 thermal cycles. • The stability of flat-tube SOFCs under thermal and redox cycling was studied. • The cell performance remained stable during the 20 short-term redox cycles. • No significant degradation happened after 8 thermal cycles with slow heating rate. • The effects of thermal and redox cycling were studied by the Ni-film anode cell. • Ni particle agglomeration on the Ni film was observed after redox cycling. [ABSTRACT FROM AUTHOR]

In-situ characterization of solid oxide fuel cells (SOFCs) under operating conditions is of great significance to mechanism studies on performance or long-term stability. In this study, real-time visualization of the two-dimensional gas distribution inside a large flat-tube SOFC is realized by built-in gas sampling tubes combined with external gas chromatography, validated by simulating calculation. The gas composition inside anode of the cell fueled with CH 4 /CO 2 is in-situ monitored during a 1000-h discharge test. Decrease in catalytic activity for methane dry reforming during the long-term test differs at different region of the cell, and is related with local carbon deposition and sintering of Ni particles. Based on these experimental results, the mechanism of cell performance degradation of the large flat-tube SOFCs under methane dry reforming conditions is discussed. • Gas composition within solid oxide fuel cell (SOFC) was in-situ monitored. • Long-term stability test of SOFC fueled with CH 4 /CO 2 was conducted for 1000 h. • Decrease of the catalytic activity for dry reforming of methane was detected. • Degradation was proved to be caused by carbon deposition and Ni sintering. [ABSTRACT FROM AUTHOR]