Solid Oxide Fuel Cells Single Cells Research Articles

Analysis of the performances of a solid oxide fuel cell fed by biogas in different plant configurations: An integrated experimental and simulative approach

Solid Oxide Fuel Cells (SOFC) are efficient, modular and fuel-flexible high temperature electrochemical devices. SOFC systems can be coupled to biogas from anaerobic digestion plants to obtain efficient and decentralized CHP systems, maximizing the valorization of biogas in virtuous waste-to-energy schemes. The main challenges for biogas-SOFC plants are related to performance stability and degradation at process level. In this work the performance and stability of an electrolyte supported SOFC single cell (100 cm2) fed with biogas mixtures derived from different integrated biogas-SOFC CHP plant configurations (hot/cold recirculation; UFf 65–85% - obtained from previous simulation work) has been analyzed with an integrated experimental and simulative approach. To support the experimental results, a chemical equilibrium model of the gas conversion processes coupled with the electrochemical conversion route is developed in MATLAB in order to simulate the gas composition at the anode outlet, which is compared and validated with experimental data obtained by Gas Chromatography (GC). Results show that suitable and stable cell performances are obtained while feeding the SOFC samples by biogas (720–800 mV; 0.16–0.2 W/cm2 at 0.25 A/cm2) where the main performance losses are related to steam content - as well as other gas species, deriving from the pre-processing of the biogas. The gas composition and UFf simulation results show good correspondence with the GC data (error range <5% for the matrix gases and <10% for water) highlighting that the SOFC processes under clean biogas can be successfully represented - to a certain extent - by a chemical equilibrium model.

(Digital Presentation) Phase-Field Modeling of the Reduction Process in Solid Oxide Fuel Cell Anode

It is well-known that the reduction process of nickel oxide-yttria-stabilized zirconia (NiO-YSZ) composite anode influences the initial performances and durability of solid oxide fuel cell. In this work, phase field method is used to simulate the reduction process of nickel oxide (NiO) in anode-supporting solid oxide fuel cell (SOFC), which captures the competition effects among diffusion, crystal phase transition of NiO to Ni, and sintering. A real three-dimensional microstructure of NiO-YSZ composite anode reconstructed using focused ion beam-scanning electron microscopy (FIB-SEM) technique is used to initialize the simulation. The simulation results are qualitatively compared to experimental results under different reduction conditions. The results reveal that the stress distribution in SOFC anode can be largely influenced by the interactions between the residual stress in yttria-stabilized zirconia (YSZ) and the reduction process. The results explain the phenomena of mechanical damage formed in SOFC single cell during reduction. Figure 1

Performance Analysis and Design of Direct Ammonia Fuel Tubular Solid Oxide Fuel Cell for Shipborne Unmanned Aerial Vehicles

Ammonia is being considered as a promising alternative to hydrogen fuel in solid oxide fuel cells (SOFCs) due to its stability and ease of storage and transportation. This study investigates the feasibility of using ammonia fuel in a tubular SOFC for shipborne unmanned aerial vehicles (UAVs). The paper develops a 3D model of a tubular-anode-supported SOFC single cell and conducts numerical simulations to analyze the impact of different operating conditions on SOFC performance. The study optimizes the SOFC’s performance by adjusting its working parameters and overall structure, revealing that increasing temperature and porosity enhance performance, but excessively high values can cause deterioration and instability in the cell. The study also finds that the cathode-supported (CS)-SOFC outperforms the anode-supported (AS)-SOFC, mainly due to its thicker cathode layer, providing better sealing and oxygen supply, resulting in a more uniform current density distribution. The paper provides valuable insights into the potential use of ammonia fuel for shipborne UAVs and offers a foundation for future research and development in the field of SOFCs. The results indicate that increasing the temperature and porosity of the SOFC can enhance battery performance, but excessive values can cause deterioration and instability in the cell. The study also highlights the impact of different operating conditions on SOFC performance, with a significant performance improvement observed in the range of 0.6–0.8 V. Additionally, the CS-SOFC outperforms the AS-SOFC due to its thicker cathode layer, but both have significant potential for development.

Characteristics of electrolyte-supported SOFC single cells using hexagonal perovskite Ba3MoNbO8.5 and Ba7Nb4MoO20 ceramics

The characteristics of two solid oxide fuel cells (SOFCs) were compared using Ba3MoNbO8.5 and Ba7Nb4MoO20 sintered at 1100 and 1300 °C, respectively, as electrolytes. The electrolyte-supported SOFC single cells, Pt ǀ Sm0.2Ce0.8O1.9 ǀ electrolyte ǀ Sm0.2Ce0.8O1.9 ǀ Pt, with an electrolyte thickness of 1.0 mm were prepared. The resistivity of the bulk + grain boundary components of Ba3MoNbO8.5 and Ba7Nb4MoO20 were 2.25k and 212 Ω cm, respectively, at 600 °C, and their apparent activation energies for ion conduction were 122.3 and 72.8 kJ mol−1, respectively at 450–600 °C. When the I–V curves were evaluated at 450–600 °C with the introduction of 3% H2 (N2 balance) and air to the anode and cathode, respectively, the open circuit voltages and maximum power outputs at 600 °C were 0.95 V and 1.3 mW cm−2 for Ba3MoNbO8.5 and 0.97 V and 9.3 mW cm−2 for Ba7Nb4MoO20, respectively.

Catalyst with CeO2 and Ni Nanoparticles on a LaCrO3-Based Perovskite Substrate for Bio-Alcohol Steam Reforming and SOFC Power Generation

A Ni/CeO2–LCeCrN catalyst was developed with a unique hierarchy of exsolved Ni and CeO2 nanoparticles dispersed on a perovskite La0.8Ce0.2–xCr0.85Ni0.15–yO3−δ (LCeCrN) substrate for steam reforming methanol, ethanol, and glycerol, producing reformate gas as fuel for solid oxide fuel cell (SOFC) power generation. Methanol, ethanol, and glycerol are almost completely steam-reformed into H2, CO, and CO2 at 450, 650, and 700 °C at a steam/carbon (S/C) ratio of 1, 2.5, and 4 with a maximum hydrogen yield of 2.2, 5.2, and 6.0 mol, respectively. The catalytic performance of Ni/CeO2–LCeCrN catalyst is durable, with no carbon deposition for methanol and slight carbon deposition for ethanol and glycerol reforming for up to 100 h, due to the presence of CeO2 nanoparticles that enhance water adsorption capability and spillover oxygen to oxidize the deposited carbon. The reformate gas is fed in sequence into the anode of an SOFC single cell for power generation. The maximum power density of the cell is comparable at 650 °C and slightly lower at 700 and 750 °C than that fueled by H2, suggesting that Ni/CeO2–LCeCrN is an excellent catalyst for steam reforming methanol, ethanol, and glycerol to produce reformate gas for SOFC power generation.

Experimental Investigation of Electrochemical Reactions Along SOFCs for Internal and External Reformed Methane

A reliable and sustainable electrical and thermal energy supply is a basic requirement for modern societies and their food supply. Solid oxide fuel cells (SOFCs) provide a highly efficient solution to generate heat and electricity independent of weather conditions, which is essential for the operation of greenhouses. They can be used in combined heat and power plants or as stand-alone systems. Furthermore, they are able to utilize a wide variety of fuels such as biogas or gasified biomass. The possibility to operate as a stand-alone system and utilizing hydrocarbons makes them suitable for application in rural communities and agricultural industry. The main component of biogas, gasified biomass and reformed hydrocarbons is methane. Methane can be directly utilized in SOFCs, but however, it can cause undesired degradation of the fuel cells anode. To reduce the risk of performance deterioration, methane can be either (i) reformed externally thus generating syngas or (ii) mixed with a sufficient amount of steam under optimized operating temperature and load for the purpose of internal reforming. During the reforming process, several chemical reactions such as the steam reforming reaction and the water gas shift (WGS) reaction take place.In this work, the off-gas compositions obtained at the reformer outlet after auto-thermal methane reforming when varying (i) steam to carbon ratio (H2O/C) and (ii) oxidizer used, e.g., air or pure oxygen, are used to fuel large planar electrolyte supported single cells with an active area of 81cm². Further tests are conducted by fuelling the SOFC single cell with methane and steam at different H2O/C. The holistic approach of this work combines thermal, electrical, electrochemical measurement methods and gas analysis to give insights in the methane utilization processes within SOFCs. Since different reactions take place as a function of the cell length and thus locally influence the cell temperature, the temperature distribution along the cell is monitored. In addition, the off-gas composition of the SOFC, the voltage and the current is continuously monitored. Furthermore, electrochemical impedance spectroscopy (EIS) measurements in combination with the distribution of relaxation time (DRT) analysis are performed at several current densities for each gas composition. Figure 1

Enhanced power density in hydrocarbon-compatible anode-supported solid oxide fuel cell facilitated by a functional anode catalyst layer

In the present study, solution combustion synthesis (SCS) is employed to prepare a hydrocarbon-compatible composite anode oxide powder containing nickel (Ni), copper (Cu), yttria-stabilized zirconia (YSZ) and gadolinia-doped ceria (GDC) (Ni0.9–Cu0.1–YSZ0.95–GDC0.05) through the single-step solution combustion method using two different fuels. The effect of fuel on the nature of the synthesized anode powder is established. Carburization studies are carried out on the synthesized anode powder to study the carbon-retarding ability. Phase stability and interface reactivity are studied by X-ray diffractometry and field emission scanning electron microscopy. The SCS-synthesized anode powder is used for the fabrication of electrolyte-supported solid oxide fuel cells (SOFCs). The fabricated SOFC single cells are characterized for their electrical and electrochemical performance. Based on their performance, it is realized that they can be used as an anode functional layer instead of the anode support. The SOFC containing the SCS-synthesized anode as the functional layer yields a high power density of 884 mW/cm2 in methane fuel at 800°C, which is higher than the reported power density of such cells. The electrode impedance and exchange current density are also derived for the SOFC.

Development of Thin Film Production Process for Lanthanum Silicate Oxyapatite Electrolyte By Tape Casting Method

Lanthanum silicate oxyapatite (LSO) has attracted attentions for applications as solid electrolyte of solid oxide fuel cells (SOFCs) and chemical sensors due to its high oxide ion conductivity along to the c-axis [1]. For applications as solid electrolyte of SOFC and chemical sensors, thin and dense electrolyte is preferable because of lower resistance of the electrolyte. Among thin film production processes, tape casting method has an advantage to produce large area thin film ceramics with low cost. In this research, we developed the tape casting process for LSO thin film electrolyte production. The conditions for preparation of slurry and sintering temperature were optimized in order to produce a dense thin film electrolyte without cracks.LSO was synthesized from La(OH)3 and SiO2 raw powders using solid state reaction method [2]. After the synthesis, the LSO was grinded by planetary ball mill in ethanol with polyethyleneimine as dispersant. Then, methyl ethyl ketone (MEK) was added in the slurry. It was known that mixture of ethanol and MEK at volume ratio of 4 : 6 becomes an azeotropic state [3]. Solid content of LSO powder in the prepared slurries was 5, 10, and 15 vol.%. A binder was added to the slurry at 5, 10, and 15 wt.%. Also, 0, 5, 10, and 15 wt.% of plasticizers were added to improve flexibility without crack formation in a green tape. After stirring the slurry, residual gas was removed in vacuum desiccator. Green film was cast at 1 mm thickness on PET (polyethyleneterephthalate) film using metal applicator. The cast film was dried in air at room tempareture. Frist, we focused on finding concentration in which the cast green tape can be peeled off from PET film without macroscopic crack. The films were heated at 773 K to remove organic additives. Optimized concentration of slurry was determined by the results that macroscopic crack and warp were not formed after the heating. This heated film produced from the optimized slurry was represented by preheated film. Final sintering tempreture was 1873 K. Warp was observed by the sintering even use of the preheated film when the film was set at free space. In order to avoid the warp, the preheated film was sandwitched by LSO ceramic disks during sintering. The disks were produced by conventional sintering using LSO powder.A sintered thin film was obtained under the conditions ; solid content at 15 vol.% ; binder concentration at 5 wt.% ; plasticizer concentration at 0 wt.% at this stage. The prepared electrolyte thin film was characterized by scanning electron microscope (SEM) to observe microstructure and film thickness. Electrical conductivity was measured by impedance spectroscopy. In addition, we produced a SOFC single cell by obtained film and platinum electrode. The results of SOFC cell performance test from 1273 K to 1073 K are shown in the figure. Thickness of the LSO thin film was 125 µm. From the cell performance test, mechanical gas leak was negligible because open circuit voltage at 1273 K was 1.04 V.Due to the use of platinum electrode, cell performance was still low at 13.1 mW cm-2 at 1273 K. To improve the cell performance, more suitable electrode materials for SOFC cell is necessary. Moreover, alignment of crystal orientation is effective to improve the cell performance by decreasing of electrolyte resistance.Reference[1] S. Nakayama, et al, J. Mater. Chem. 5 (1995), 1801-1805[2] K. Kobayashi, et al., J. Ceram. Soc. Japan. 123 (2015), 274-279[3] S. Beaudet Savignat et al., J. Eur. Ceram. Soc. 27 (2007), 673-678 Figure 1

In-situ exsolved NiFe alloy nanoparticles on Pr0.8Sr1.2(NiFe)O4-δ for direct hydrocarbon fuel solid oxide fuel cells

NiFe alloy (NFA) nanoparticles decorated Ruddlesden-Popper (RP) type layered perovskite structure Pr0.8Sr1.2(NiFe)O4-δ (RP-PSNF) have been fabricated by in-situ reduction of cubic perovskite Pr0.32Sr0.48Ni0.2Fe0.8O3-δ (P–PSNF) in H2 at 800 °C. When used as the solid oxide fuel cell (SOFC) anode material, the RP-PSNF-NFA based ceramic anode demonstrates a comparable catalytic activity to Ni-based anode. The SOFC single cell with RP-PSNF-NFA-Gd0.2Ce0.8O2−δ (GDC) anode exhibits a maximum power density of 983 and 770 mW cm−2 in humidified H2 and C3H8 at 800 °C, respectively. More importantly, the single cell shows a high durability at the current density of 250 mA cm−2 in humidified C3H8 at 800 °C, demonstrating an excellent coking resistance. Overall, this work suggests that RP-PSNF-NFA is a promising anode for direct hydrocarbon fuel SOFCs.

Co-fired anode-supported solid oxide fuel cell for internal reforming of hydrocarbon fuel

Hydrocarbon-based solid oxide fuel cell (SOFC) is being projected as one of the possible alternatives to conventional internal combustion engines. However, the conventional Ni–YSZ anode is prone to carburization in the presence of hydrocarbon fuels. In the present study, an optimized Ni–Cu-based anode composition (Ni0.9–Cu0.1–YSZ0.95–GDC0.05) has been evolved based on accelerated carburization studies and phase analysis by X-ray diffractometry and X-ray photoelectron spectroscopy. The electrochemical parameters have been derived for the optimized anode composition, and its exchange current density is estimated to be 76.3 mA cm−2 at 780 °C. The main advantage of the optimized anode is its suitability for co-firing with the electrolyte. Using the optimized anode composition, anode-supported SOFC single cells (ASCs) have been fabricated and their electrical and electrochemical performances have been evaluated and compared with conventional ASC. The anode-supported co-cast SOFC with the optimized anode composition exhibits a power density of 436 mW cm−2 at 850 °C and 0.5 V with methane as fuel.

Thermodynamic Analysis of Solid Oxide Fuel Cell Integrated System Fuelled by Ammonia from Struvite Precipitation Process

AbstractEnergy and exergy performance of ammonia fuelled solid oxide fuel cell (SOFC) integrated system in wastewater treatment plants (WWTPs) is evaluated in this study. Ammonia can be recovered through a struvite precipitation process in the form of an ammonia‐water mixture (with 14 mol.% ammonia) and used as a carbon‐free fuel. A series of experiments has been conducted for SOFC single cell to evaluate the performance with different ammonia‐water mixture ratios. An ammonia‐SOFC system was modeled in Cycle Tempo for detailed thermodynamic analysis. The heat from the electrochemical reaction in the SOFC and catalytic combustion in an afterburner is used in the struvite decomposition process. However, the generated heat is not sufficient to meet the heat demand of the struvite decomposition reactor. To improve the sustainability of the system in terms of heat demand, the system can be integrated into a heat pump assisted distillation tower, meanwhile, the ammonia concentration of the fuel stream increases. Increasing the ammonia concentration to 90 mol.% increases the energy and exergy efficiencies of the SOFC system. The net energy efficiency of the integrated system with a heat pump assisted distillation tower is 39%, based on the LHV of the ammonia‐water mixture.

Tubular solid oxide fuel cells fabricated by a novel freeze casting method

AbstractFreeze casting is an established method for fabricating porous ceramic structures with controlled porosity and pore geometries. Herein, we developed a novel freeze casting and freeze drying process to fabricate tubular anode supports for solid oxide fuel cells (SOFCs). Freeze casting was performed by injecting aqueous anode slurry to a dual‐purpose freeze casting and freeze drying mold wrapped with peripheral coils for flowing a coolant. With the use of an ice barrier layer, proper control of the experimental setup, and adjustments in the drying temperature profile, complete drying of the individual anode tubes was achieved in 4 hours. The freeze‐cast anode tubes contained radially aligned columnar pore channels, thus significantly enhancing the gaseous diffusion. SOFC single cells with conventional Ni/yttria‐stabilized zirconia/strontium‐doped lanthanum manganite materials were prepared by dip coating the thin functional layers onto the anode support. Single cell tests showed that the concentration polarization was low owing to the highly porous anode support with directional pores. With H2/N2 (1:1) fuel, maximum power densities of 0.47, 0.36, and 0.27 W/cm2 were recorded at 800°C, 750°C, and 700°C, respectively. Our results demonstrate the feasibility of using freeze casting to obtain tubular SOFCs with desired microstructures and fast turn‐around times.

Applicability of the SOFC technology for coupling with biomass-gasifier systems: Short- and long-term experimental study on SOFC performance and degradation behaviour

Coupling biomass gasification with high temperature Solid Oxide Fuel Cells (SOFCs) is a promising solution to increase the share of renewables and reduce emissions. The quality of the producer gas used can, however, significantly impact the SOFC durability and reliability. The great challenge is to ensure undisturbed operation of such system and to find a trade-off between optimal SOFC operating temperature and system thermal integration, which may limit the overall efficiency. Thus, this study focuses on experimental investigation of commercial SOFC single cells of industrial size fueled with different representative producer gas compositions of industrial relevance at two relevant operating temperatures. The extensive experimental and numerical analyses performed showed that feeding SOFC with a producer gas from a downdraft gasifier, with hot gas cleaning, at an operating temperature of 750 °C represents the most favorable setting, considering system integration and the highest fuel utilization. Additionally, a 120 h long-term test was carried out, showing that a long-term operation is possible under stated operating conditions. Local degradation took place, which can be detected at an early stage using appropriate online-monitoring tools.

Numerical Simulation of Planar SOFC Single Cell Fueled by Hydrogen, Nitrogen and Water Vapor Considering Fuel Gas Leakage from Cell Side

In this study, the authors developed a simulation program for a planar solid oxide fuel cell (SOFC) single cell with SSZ electrolyte fueled by hydrogen, nitrogen and water vapor. Firstly, polarization (i - V) curves were measured and compared with the corresponding numerical ones. As a result, a very good agreement between the measured and simulated values was observed. Next, simulations in case where a fuel gas leakage occurs in the SOFC were carried out. Based on the numerical findings, influence of the fuel gas leakage on cell performances was investigated. As a result, the fuel gas leakage affects fuel supply to each channel and provokes serious shortage of the fuel gas at downstream sides in both side channels where the crack is assumed for the fuel gas leakage. Thereby, each distribution in the SOFC is impacted and the single cell voltage is reduced.

Fabrication and characterization of Intermediate-Temperature Solid Oxide Fuel Cell (IT-SOFC) single cell using Indonesia’s resources

Solid Oxide Fuel Cell (SOFC) is one of the promising developments in the fuel cell system. SOFC can be applied to micro-scale combined heat and power generation (micro CHP) as a power plant in housing. Recently, intermediate-temperature SOFC (500-700°C) is being widely developed since cheaper than the conventional SOFC (∼1000°C). Intermediate-temperature and conventional SOFC are less developed in Indonesia due to expensive electrode and electrolyte materials, such as Yttria and Lanthanum, which are not available in Indonesia. This study aims to develop a novel disk-shaped single cell SOFC based on materials from Indonesia’s resources. Calcia Cobalt Zinc Oxide (CCZO) is an alternative cathode to replace conventional cathode such as Lanthanum Strontium Manganite (LSM). CCZO cathode was made using spray coating. Calcia can also substitute Ytrria as a stabilizer of zirconia in electrolyte fabrication. Calcia-stabilized Zirconia (CSZ) electrolyte was produced using spray coating. NiO anode was fabricated through hydraulic pressing. The single cell was operated using hydrogen (125 sccm) as a fuel and ambient air (500 sccm) as an oxidant. The results showed an open-circuit voltage (OCV) of 0.577, 0.558, and 0.513 V and produced the maximum power densities of 1.4, 2.8, and 10 mW m−2 at 500, 600, and 700°C, respectively. Measurement of the cell impedance indicated that the overall resistance decreased with increasing temperature.

Chemical synthesis of materials based on calcium zirconate for solid oxide fuel cells (SOFC)

AbstractFuel cells allow the production of energy from a clean electrochemical reaction. Among various types, the solid oxide fuel cell (SOFC) operates at high temperatures, allowing the conversion of hydrogen fuel into electricity, where water is generated as a by‐product. Strontium‐doped lanthanum manganite (La1‐xSrxMnO3, LSM) is commonly used as a cathodic material in traditional high‐temperature solid oxide fuel cells. Nowadays, the operating temperature of SOFCs should be reduced to 600–800°C due to improved fine electrolyte production techniques and the use of some intermediate temperature electrolytes. The LSM is not a suitable cathode for SOFCs operating in this temperature range, since it does not have a high enough conductivity and its electrochemical activity is very low as well. In this article, the performance improvement of LSM is described by mixing with calcium zirconate. The composite ceramic materials CaZrO3−La0.6Sr0.4MnO3, CaZrO3−NiO, and CaZrO3 were synthesized by combustion method, for application as a SOFC single cell. The results prove that the synthesized materials have potential to be used in a SOFC cell. At 800°C, was confirmed the CaZrO3 formation. Through Electrochemical impedance spectroscopy, the analysis presented low activation energy and the materials have been demonstrated to be compatible, an important fact to construct a suitable SOFC cell. The obtained activation energy was 0.90, 0.85, and 0.51 eV for the electrolyte, the anode and the cathode, respectively.

SOFC anodes impregnated with noble metal catalyst nanoparticles for high fuel utilization

Redox-stable solid oxide fuel cell (SOFC) anodes are developed in order to improve durability at higher fuel utilization, as a possible alternative to conventional Ni-zirconia cermet anodes. Ce0.9Gd0.1O2 (GDC) is utilized as a mixed ionic and electronic conductor (MIEC), in combination with Sr0.9La0.1TiO3 (LST) as an electronic conductor. The stability of noble metals (Rh, Pt, and Pd) is analyzed via thermochemical calculation of stable phases. Noble metal catalyst nanoparticles are incorporated via co-impregnation with GDC. The electrochemical characteristics of SOFC single cells using these anode materials are investigated in highly-humidified H2 at 800 °C. Their stability at high fuel utilization is analyzed. These co-impregnated anodes with highly dispersed noble metal catalysts on the LST-GDC conducting backbones, achieve high IV performance comparable to conventional Ni-cermet anodes. The co-impregnated anodes also achieve considerably high catalytic mass activity. At higher oxygen partial pressure, where the Ni catalyst can be deactivated by oxidation, these noble catalysts are thermochemically stable in the metallic state, and tolerant against oxidation. This class of alternative catalyst, impregnated with low-loading of noble metals could contribute to stable operation in the downstream region of SOFC systems. A simple cost analysis indicates a tolerance of using noble metals, provided their loading is sufficiently low.

Optimization of an integrated biomass gasifier-fuel cell system: An experimental study on the cell response to process variations

Coupling biomass gasification with high temperature Solid Oxide Fuel Cells (SOFCs) is a promising solution to increase the share of renewables and raise energy efficiency. Optimal system integration and high durability of its components are both required for this purpose. Moreover, system optimization may ask for a compromise between optimal SOFC operating temperature and system thermal integration. Nevertheless, the producer gas quality and operating temperature have a noticeable impact on SOFC performance, which has to be considered.In order to address the challenges mentioned, this study focuses on experimental investigation of commercial SOFC single cells of industrial size fuelled with different gas mixtures. Namely, typical producer gas compositions from downdraft fixed bed gasification with air (with and without drying) and fluidized bed gasification with steam are considered. In addition to that, the effect of temperature variation is analysed. The results show that, although a higher cell temperature (800°C) and a dry product gas composition lead to higher efficiencies, it is feasible to run the SOFC on wet producer gas at lower cell temperatures (750°C). Despite a decreased efficiency, this would optimize the gasifier-SOFC coupling. Moreover, the presence of water in the producer gas (when drying is not included) reduces the possibility of carbon deposition, thus increasing the cell durability. Therefore, cases with low cell temperatures and presence of water in the gas should be considered as viable alternatives for the system coupling and possible SOFC degradation in such cases is going to be extensively analysed.

Co–Cu–YSZ–GDC as an anode material for internal reforming SOFC?

A solid oxide fuel cell (SOFC) is a fuel-flexible device, and, apart from using pure hydrogen, it can utilize carbon monoxide, methane or any other higher hydrocarbons. Moreover, it can tolerate some degree of common fossil fuel impurities, such as ammonia and chlorides. It can even utilize the biogas derived from decomposable waste. However, the propensity of the state-of-the-art anode (nickel (Ni)–yttria-stabilized zirconia (YSZ)) toward carburization limits the ability of SOFCs to realize such a goal. In an attempt to develop a carbon-resistant anode system, the present work explores the carburization studies of a cobalt (Co)–copper (Cu) bimetallic anode system and fabrication of a cobalt–copper–YSZ–gadolinia-doped ceria (GDC) anode composite. The effect of alloying cobalt with copper and addition of rare-earth oxide on carburization has also been studied in detail. The anode composition was characterized for crystal structure, microstructure and redox stability. Using the optimized anode composition, SOFC single cells have been fabricated and their electrical and electrochemical performances have been evaluated. The investigated Co0·9Cu0·1YSZ0·95GDC0·05 anode has undergone severe agglomeration during the fabrication and operation of the cell, which resulted in inferior performance. The surface-segregated copper acted as a poor catalyst for hydrocarbon oxidation.

Design of Active Sites on Nickel in the Anode of Intermediate-Temperature Solid Oxide Fuel Cells using Trace Amount of Platinum Oxides.

In recent years, the lowering of the operation temperature of solid oxide fuel cells (SOFCs) has attracted much attention owing to the trade-off between the best performance and the life span of SOFCs. For this challenge, new active sites on the Ni surfaces in a Nickel-Yttria-Stabilized Zirconia (Ni-YSZ) cermet anode of SOFCs have been created by deposition of trace amounts of platinum oxide (PtOx ) followed by an activation step of the anode at 1073 K in a hydrogen flow. The internal resistance (IR) free value (185 mA cm-2 at 0.8 V) observed for the single cell with an anode sputtered with a trace amount of PtOx (Pt content in anode: from 9 to 91 ppm) at 973 K is conspicuously higher than that of a similar single cell with a nonsputtered cermet anode (85 mA cm-2 ) at 0.8 V and 1073 K. Transmission electron microscopy microanalysis shows that the defect structure is formed on a partially oxidized Ni surface by active Pt species. Also, surface atomistic simulation on NiO (111) predicts the formation of Frenkel defect clusters with Pt cations, which partially cover the Ni surface. The formation of Frenkel defect clusters on the partially oxidized Ni surface (i.e., creation of new active sites for formation of water molecules) promotes the anode reaction, resulting in improvements in the anode performance of SOFC single cells at 973 K. Design of the aforementioned new active sites on Ni through sputtering of trace amounts of PtOx provides a great opportunity for "radical innovation" in the design of intermediate-temperature SOFCs.