Solid Oxide Fuel Cell Anode Research Articles

Prediction of electrode microstructure of SOFC with conditional generative adversarial network

Solid oxide fuel cell (SOFC) is a technology with great potential for hydrogen energy utilization. However, the complex three-dimensional (3D) structure of SOFC anode is affected by various parameters during the fabrication process. This work develops a microstructure prediction model based on generative adversarial network (GAN) that could generate anode microstructures under different fabrication processes. In this GAN model, the training data and effects of fabrication parameter on structure are obtained from focused ion beam scanning electron microscope (FIB-SEM) observation and calculation. These effects are applied as principles of physical constraints to additionally train the generator by controlling statistical parameters, such as porosity and average particle size. The model is further validated by comparing the generated structure with the real structure from experiment. The generated structures show well visual and quantified consistency with the real structures. The model has the potential to guide the structural optimization of porous electrodes.

Tracking Microstructural Evolution of the Ni-Cermet Fuel Electrode in Solid Oxide Electrolyzers Using X-Ray Nano Computed Tomography

Decarbonization of hydrogen production is critically important to the renewable energy economy, indeed, the US Department of Energy recently released the Hydrogen Shot, setting the target at reducing the cost of clean hydrogen to $1 per kilogram in 1 decade. Of the electrolysis technologies that might meet the Hydrogen Shot goal, high temperature electrolysis based on solid oxide electrolysis cells (SOECs) is particularly promising due to its high efficiency and the ability to avoid the use of expensive and scarce metal catalysts.1 However, the harsh environment (high temperature, reducing/oxidizing environments, interfacial compatibility, and high current density) that SOECs are operated in presents a major challenge with respect to material stability. To reach relevant SOEC lifetimes on the order of sixty to eighty thousand hours of operation, drastic improvements in cell durability must be made. However, ageing cells on the order of tens of thousands of hours to characterize physicochemical changes at the material level to inform mitigation strategies is prohibitively slow. Accelerated stress test (AST) protocols must be developed to activate degradation mechanisms more quickly in the SOEC, enabling comparison of different materials and fabrication methods in a timely fashion. This approach will enable mitigation strategies to directly address degradation pathways identified as a function of testing conditions, SOEC physicochemical properties, and cell processing history.Several possible degradation pathways for SOECs have been hypothesized and identified, including cation migration into/across the electrolyte, particle coarsening in the electrodes and subsequent change in porosity, undesired phase formation, and others.2 These can lead to increased electrical resistance, decreased mass transport rate of gaseous reactants or products, and deactivation of active sites through formation of inactive species. Particular attention has been paid to microstructural evolution of the fuel electrode comprised of Ni and yttria-stabilized zirconia (YSZ). The hydrogen evolution reaction (HER) occurs electrocatalytically at the triple-phase boundary (TPB) of Ni (catalysis and electron conduction) YSZ (oxygen ion conduction) and pore space (gas phase transport), and any change in distribution of these three phases can result in both increased resistances and loss of active HER sites. Therefore, extensive effort has been made to understand Ni redistribution and optimize the Ni-YSZ microstructure to decrease the rate of change in Ni properties. However, there is still debate within the literature on the exact mechanism for Ni redistribution as both a surface hydroxide mediated transport and a particle curvature-based hypothesis have been suggested.3 Furthermore, clear correlation of degradation symptoms, including Ni particle size change, migration towards/away from the electrolyte, Ni/YSZ de-wetting, and isolation of pore space/TPB with variations in initial microstructure or different operating conditions is still lacking.This work focuses on illuminating these relationships between performance losses in Ni-YSZ fuel electrodes with dynamic, AST operating conditions using X-ray nanoscale computed tomography (nano-CT). Nano-CT yields 3D microstructural information through image segmentation, which can then be used to track changes in TPB density, phase fraction depth profile, phase size distribution, and phase connectivity/isolated fractions.4 This extensive set of properties can aid in identifying whether loss of fuel electrode performance is due to Ni coarsening, de-wetting, or migration. Understanding how Ni migration may be influenced by operating conditions will inform efforts to effectively suppress and slow degradation of the fuel electrode. These efforts will drive SOEC technology advances towards longer operating lifetimes, enabling cheaper lifetime hydrogen production. References (1) Hauch, A.; Küngas, R.; Blennow, P.; Hansen, A. B.; Hansen, J. B.; Mathiesen, B. V.; Mogensen, M. B. Recent Advances in Solid Oxide Cell Technology for Electrolysis. Science 2020, 370 (6513).(2) Moçoteguy, P.; Brisse, A. A Review and Comprehensive Analysis of Degradation Mechanisms of Solid Oxide Electrolysis Cells. Int. J. Hydrog. Energy 2013, 38 (36), 15887–15902.(3) Mogensen, M. B.; Chen, M.; Frandsen, H. L.; Graves, C.; Hauch, A.; Hendriksen, P. V.; Jacobsen, T.; Jensen, S. H.; Skafte, T. L.; Sun, X. Ni Migration in Solid Oxide Cell Electrodes: Review and Revised Hypothesis. Fuel Cells 2021, fuce.202100072.(4) Heenan, T. M. M.; Bailey, J. J.; Lu, X.; Robinson, J. B.; Iacoviello, F.; Finegan, D. P.; Brett, D. J. L.; Shearing, P. R. Three-Phase Segmentation of Solid Oxide Fuel Cell Anode Materials Using Lab Based X-Ray Nano-Computed Tomography. Fuel Cells 2017, 17 (1), 75–82. Figure 1

Simulation of Stack-Integrated Autothermal Reformer and Solid Oxide Fuel Cells for Operation in Aircraft Engines

Renewable liquified natural gas provides a potential sustainable aviation fuel, but with a volumetric energy density around 70% of conventional jet fuel. As such, alternative aircraft power plants such as hybrid gas turbine (GT) / solid oxide fuel cells (SOFCs) have been proposed to increase fuel conversion efficiency and support hybrid electric propulsion concepts. To enable reliable SOFC operation within aircraft gas turbine flow paths, stack architectures must be identified that sustain very high-power densities with direct inline air feeds from the gas turbine compressor outlet. Typical aircraft compressor outlet temperatures are below SOFC operating temperatures but high enough to light-off a catalytic autothermal reformer (ATR). The ATR combined with an air heat exchanger (HX) can preheat anode and cathode streams to desirable inlet temperatures above 500 °C for intermediate-temperature SOFCs that utilize gadolinia-doped ceria (GDC) electrolytes or thin-film, yttria-stabilized zirconia (YSZ) electrolytes. By packaging the inline ATR/HX within the SOFC stack and mixing partial anode exhaust recycle and bleed air with the ATR fuel stream, a volumetrically efficient inline stack architecture is being designed for demonstration at conditions simulating an aircraft gas-turbine compressor outlet. The combination of the ATR/HX and the high-power-density SOFC imposes significant temperature gradients within the stack that can impact performance. To assess suitable operating conditions and preferred designs for the ATR/HX/SOFC operating on renewable natural gas, a 3-D multi-physics CFD model has been developed. Simulation results for SOFCs with thin-film YSZ or GDC electrolytes show the challenge maintaining high-power densities while maintaining the full stack within expected temperature limits for expected cell materials.The ATR/HX/SOFC stack design includes the upstream ATR/HX, 3.6 cm in length. The ATR flow path is filled by a porous mesh with a washcoat-supported Pt catalyst for light off of CH4/bleed air/H2O inlet mixtures. The air-side flow paths in the ATR/HX are etched parallel channels that extract heat from the exothermic ATR reactions. The ATR/HX outlets feed the SOFC anode and cathode flow paths respectively. For this study, the SOFC membrane electrode assembly (MEA) 10 cm in length, consists of a porous Ni-YSZ anode-support (400 mm thick), dense YSZ or GDC electrolytes (≤ 20 mm thick), and a perovskite-YSZ composite cathode (35 mm thick). The anode flow passages over the support involve a high-porosity mesh that enables current collection. The cathode flow channels are etched ribs that enable high air flow rates to support high power density with adequate SOFC stack cooling. The ATR/HX/SOFC design has been incorporated into an ANSYS Fluent model to explore how integration of the ATR/HX in the stack can enable high-power performance of the SOFC while supporting light-off of the ATR fuel stream at aircraft compressor outlet conditions. The ANSYS Fluent model uses customized user-defined functions to handle the heterogeneous catalytic CH4oxidation surface chemistry for the ATR (supported Pt catalyst [1]) and for internal CH4 reforming in the Ni/cermet anode support in the SOFC [2]. The model simulates non-isothermal operation of a single ATR/HX/SOFC cell, representative of a full stack, at various inlet flow temperatures, pressures, flow rates, and fuel stream compositions, which are set by anode exhaust recycle fraction.CFD model results for thin-film YSZ-electrolyte MEAs illustrate a strong dependence of SOFC power density on the anode recycle fraction and cathode bleed air splits into the ATR fuel stream. For a 400 °C air inlet, the short ATR/HX is capable of achieving near-equilibrium CH4 conversion to an H2-rich reformate while preheating the cathode inlet up to 500 °C. Simulations over a range of anode recycle fractions show that lower recycle fractions increase ATR outlet temperatures and H2 mole fractions with SOFC power densities reaching 2.0 W cm-2, but at the risk of excessive anode temperatures and large temperature gradients across the length of the MEA. Increased cathode excess air ratios can lower the temperatures at the expense of stack power density. Higher anode recycle fractions decrease the temperature rise across the length of the MEA, but also at the expense power density. Further studies with GDC electrolytes based on recent GDC SOFC model developments [3] will explore how high-power densities of GDC can be supported within its operating temperature constraints.

Ruddlesden-Popper perovskite anode with high sulfur tolerance and electrochemical activity for solid oxide fuel cells

Solid oxide fuel cells (SOFCs) are regarded as attractive electrochemical energy conversion devices owing to their exceptional efficiencies and superb fuel flexibility. However, their widespread implementations are remarkably restricted by the inferior sulfur tolerance of state-of-the-art nickel-based cermet anodes under practical conditions. Herein, a layered NaLaTiO4 (NLTO) perovskite oxide with Ruddlesden-Popper structure is designed as a new anode for SOFCs operating on sulfur-containing fuels. After impregnating NLTO into a samaria-doped ceria (SDC) scaffold, such impregnated nanocomposite anode exhibits high electrochemical activity, sulfur tolerance and stability in H2S-containing fuels due to the polar layered structure, abundant oxygen vacancies, superior surface basicity and water storage capability, leading to the efficient removal of the deposited/adsorbed sulfur on the surface of this nanocomposite anode. The electrochemical activity of the NLTO-based composite anode for fuel oxidation is further improved by adding nickel nanoparticles through impregnation, showing enhanced power outputs and considerable operational stability in H2S-containing fuels. This study provides a new, high-performing and sulfur-resistant anode for SOFCs, which may promote the commercialization of this technology.

Designing tortuous gas diffusion path for hydrogen oxidation reaction and stability of solid oxide fuel cell: An engineered microstructural aspect in anode functional layer

Commercialization of solid oxide fuel cell (SOFC) is restricted due to long term performance degradation. SOFC is activated by diffusion of gasses through porous electrodes to the electrochemical active sites termed as triple phase boundary (TPB). Among all other parameters, tortuosity influences the functionality of TPB and is responsible for gas transport which relates its bulk diffusion and its migration through the porous electrode. The novelty of present research lies in designing of optimum tortuous gas diffusion path for effective hydrogen oxidation reaction through engineered morphology of anode functional layer. The study involves the fabrication of anode for planar SOFC using four configurations. Configuration A and B involves anode monolith synthesized through conventional route [(40 vol % Ni in dispersed-8 mol % Yttria stabilized zirconia (SZ)] and functional core-shell Ni@SZ. Configuration C (trilayer anode, TLA) is designed to have graded matrix with conventional Ni-SZ (fuel inlet side), 28 vol% Ni@SZ acting as active layer and 32 vol % Ni@SZ sandwiched in between. Configuration D consists of Ni@SZ as the active layer onto conventional Ni-SZ support. TLA is found to have minimum tortuosity (τ = 2) with maximum cell endurance for 2000 h (2.06–8.2 %/1000 h@800 °C under load). Ni@SZ with unimodal pore distribution is capable of reducing the activation barrier for charge migration (14 kJmol-1) compared to Ni-SZ (32 kJmol-1) with multimodal pores. This results in higher redox tolerance for Configuration B-D (4–7 % conductivity degradation/20 cycles) compared to Configuration A (27% conductivity degradation/20 cycles). Post mortem analyses of microstructure support the retention of core-shell morphology of Ni@SZ with lower deterioration.

Boosting the Performance and Stability of Perovskites by Construction of NiFe Alloy and PrOx Heterogeneously Structured Composites for High‐Performance Solid Oxide Fuel Cell Anode

Boosting the Performance and Stability of Perovskites by Construction of NiFe Alloy and PrO_x Heterogeneously Structured Composites for High‐Performance Solid Oxide Fuel Cell Anode

Preparation of spherical NiO-8YSZ composite powder through spray drying

Homogeneous sphere NiO-8YSZ composite powder with a narrow size distribution is significant for the fabrication of high-quality solid oxide fuel cell (SOFC) anodes. In this study, spray drying was used to prepare evenly distributed and spherical NiO-8YSZ composite particles used for the fabrication of SOFC anodes. The result showed that the particles prepared with a solid content of 65 wt %, atomizing pressure of 60 kPa, drying temperature of 180 °C, and sintering at 1200 °C for 2 h exhibited the best holistic quality with high sphericity (90 % over 0.84), narrow size distribution (D10 = 27.78 μm, D90 = 45.49 μm), high collection rate (70 %), and low content of unstable phases. The influence of these main parameters on the quality of the prepared particles was investigated and discussed as well. It was found that the solid content and the atomizing pressure demonstrated opposite effects on the particle size, with the former showing a positive correlation and the latter showing a negative correlation. The drying temperature decided the agglomeration degree of the prepared powder, which was involved in the presence of grape-like particles. In addition, the collection rate appeared to be positively correlated with the solid content and the atomizing pressure. The atmospheric plasma sprayed coating fabricated using the sprayed-dried powder prepared with the optimal parameters demonstrated significantly improved micromorphology and structure when compared with the coating fabricated using the mechanical mixed composite powder, which proved the prominent advantage of the powder produced through this spray drying method. All these progresses were considered good instructions for the studies on powder granulation and its applications in manufacturing high-quality coating materials.

Evaluation of anode support microstructure in solid oxide fuel cells using virtual 3D reconstruction: A simulation study

In this study, the impact of microstructural properties of the anode support layer (ASL) composed of catalyst, electrolyte and pore phases on the performance of solid oxide fuel cell (SOFC) is investigated. Synthetic SOFC anode microstructures, comprising two layers including the anode functional layer (AFL), where electrochemical reactions take place, are generated using an open-source software. Different configurations of the anode support layer with various particle sizes and volume fractions of the catalyst and electrolyte phases for different porosities are combined with a consistent AFL to isolate the effect of ASL microstructural parameters. The triple phase boundary (TPB) density, chosen as a useful metric monitoring the anode performance, is then quantitively determined for each anode layer and entire anode in all reconstructed microstructures. The results demonstrate that the microstructure of ASL significantly influences the anode and thus cell performance by impacting reactant gas supply and current collection, emphasizing the necessity for meticulous design. Specifically, ASL microstructures with low volume fractions of Ni and the pore phase, and/or substantial differences between the volume fractions of the phases, are observed to result in discontinuous phase networks, which deactivate TPBs in AFL.

Generative Artificial Intelligence for Designing Multi-Scale Hydrogen Fuel Cell Catalyst Layer Nanostructures.

Multiscale design of catalyst layers (CLs) is important to advancing hydrogen electrochemical conversion devices toward commercialized deployment, which has nevertheless been greatly hampered by the complex interplay among multiscale CL components, high synthesis cost and vast design space. We lack rational design and optimization techniques that can accurately reflect the nanostructure-performance relationship and cost-effectively search the design space. Here, we fill this gap with a deep generative artificial intelligence (AI) framework, GLIDER, that integrates recent generative AI, data-driven surrogate techniques and collective intelligence to efficiently search the optimal CL nanostructures driven by their electrochemical performance. GLIDER achieves realistic multiscale CL digital generation by leveraging the dimensionality-reduction ability of quantized vector-variational autoencoder. The powerful generative capability of GLIDER allows the efficient search of the optimal design parameters for the Pt-carbon-ionomer nanostructures of CLs. We also demonstrate that GLIDER is transferable to other fuel cell electrode microstructure generation, e.g., fibrous gas diffusion layers and solid oxide fuel cell anode. GLIDER is of potential as a digital tool for the design and optimization of broad electrochemical energy devices.

Overall scheme design of a closed solid oxide fuel cell hybrid engine for ships

A scheme of compact closed solid oxide fuel cell hybrid engines for ship power and propulsion on ships is proposed. A zero-emission closed engine at the effective equivalence ratio of 1 is achieved by recirculating water and fuelling by liquid hydrocarbon fuel and oxygen. The adiabatic pure oxygen reforming temperature of the reformer is higher than the specified anode inlet temperature. A turbine is placed in front of the solid oxide fuel cell anode. Detailed potential distributions are considered using a two-dimensional solid oxide fuel cell model, and thermodynamic models of the hybrid engine are built. The performance of the reformer is more sensitive to the oxygen-carbon ratio rather than the steam-carbon ratio, which leads to a huge change of the pressure ratio of the turbine. Therefore, the power ratios of turbines and SOFC are also affected by the oxygen and steam carbon ratio and excess oxygen coefficient. The optimized power ratio is 1.02–1.13, which results in a significant change in the efficiency of the engine. Under the specified operating conditions, the engine can achieve a high efficiency of 67 %. Under the off-design conditions, with the increase of the mass flow of fuel or the current density, the power of the engine can be changed from 20 % to 160 % of the designed power.

Quantifying Microstructure Features for High-Performance Solid Oxide Cells.

The drive for sustainable energy solutions has spurred interest in solid oxide fuel cells (SOFCs). This study investigates the impact of sintering temperature on SOFC anode microstructures using advanced 3D focused ion beam-scanning electron microscopy (FIB-SEM). The anode's ceramic-metal composition significantly influences electrochemical performance, making optimization crucial. Comparing cells sintered at different temperatures reveals that a lower sintering temperature enhances yttria-stabilized zirconia (YSZ) and nickel distribution, volume, and particle size, along with the triple-phase boundary (TPB) interface. Three-dimensional reconstructions illustrate that the cell sintered at a lower temperature exhibits a well-defined pore network, leading to increased TPB density. Hydrogen flow simulations demonstrate comparable permeability for both cells. Electrochemical characterization confirms the superior performance of the cell sintered at the lower temperature, displaying higher power density and lower total cell resistance. This FIB-SEM methodology provides precise insights into the microstructure-performance relationship, eliminating the need for hypothetical structures and enhancing our understanding of SOFC behavior under different fabrication conditions.

Atomic S, H and C adsorption on MnO(001) surface and the interaction between H and LaCrO3(001) surface: A computational analysis

S poisoning and C deposition are key factors to cause performance degradation of solid oxide fuel cells (SOFC) anodes. The adsorptions of atomic S, H and C on MnO(001) surface and atomic H on LaCrO3(001) surface are systematically investigated using density functional theory (DFT) calculations. The analysis of surface relaxation shows that surface Mn ion slightly moves toward the slab center and surface O ion moves outward on MnO(001) surface. According to the result of adsorption energy, it can be inferred that the MnO weakens the adsorption of atomic S with lower adsorption energies compared to LaCrO3 surface. In addition, the findings show that the preferred site for atomic H adsorption is O site, with the adsorption energy of －1.361 eV, which results in the formation of –OH surface species. Compared to O sites on LaCrO3(001) surface, the atomic H is found to interact weakly with the La and Cr sites. The distances and charges transfer between adsorbate and substrate have also been analyzed. The obtained results are expected to provide some fundamental information for future research on mechanism of S poisoning and C deposition on SOFC anodes.

Cation doping and oxygen vacancies in the orthorhombic FeNbO4 material for solid oxide fuel cell applications: A density functional theory study.

The orthorhombic phase of FeNbO4, a promising anode material for solid oxide fuel cells (SOFCs), exhibits good catalytic activity toward hydrogen oxidation. However, the low electronic conductivity of the material specifically in the pure structure without defects or dopants limits its practical applications as an SOFC anode. In this study, we have employed density functional theory (DFT + U) calculations to explore the bulk and electronic properties of two types of doped structures, Fe0.9375A0.0625NbO4 and FeNb0.9375B0.0625O4 (A, B = Ti, V, Cr, Mn, Co, Ni) and the oxygen-deficient structures Fe0.9375A0.0625NbO3.9375 and FeNb0.9375B0.0625O3.9375, where the dopant is positioned in the first nearest neighbor site to the oxygen vacancy. Our DFT simulations have revealed that doping in the Fe sites is energetically favorable compared to doping in the Nb site, resulting in significant volume expansion. The doping process generally requires less energy when the O-vacancy is surrounded by one Fe and two Nb ions. The simulated projected density of states of the oxygen-deficient structures indicates that doping in the Fe site, particularly with Ti and V, considerably narrows the bandgap to ∼0.5eV, whereas doping with Co at the Nb sites generates acceptor levels close to 0eV. Both doping schemes, therefore, enhance electron conduction during SOFC operation.

Onboard Miniature Jet Fuel Desulfurizer for Mobile Fuel Cell Power Systems

Owing to its high energy density and wide availability, jet fuel is a promising fuel for solid oxide fuel cell (SOFC) power systems. However, fuel‐reforming catalysts and SOFC anodes are easily poisoned by sulfur compounds present in the jet fuel. Therefore, effective removal of sulfur from the jet fuel is essential before its feeding to the SOFC system. Herein, a novel adsorptive desulfurization reactor for onboard desulfurization of jet fuel in mobile SOFC systems is developed. A laser‐based 3D printing method is used to fabricate the one‐piece stainless steel reactor that significantly simplifies the assembly and reduces the overall weight. The desulfurization performance of the reactor is evaluated using a regenerable nickel‐based sorbent under varying operating conditions. A strong influence of temperature and fuel flow rate on the desulfurization performance is observed. The results confirm that the developed desulfurization system is capable of reducing the sulfur content in jet fuel to a few ppm to sub‐ppm level. The proposed desulfurization system offers unique advantages in terms of geometric design flexibility, space optimization, scalability, and modularity for any onboard and/or on‐demand deep desulfurization needs in addition to fuel cell power systems for transport and portable applications.

Degradation of solid oxide fuel cell anodes by the deposition of potassium compounds

Alkali contents with low melting points in the ash of woody biomass vaporize during the biomass gasification process, damaging various downstream energy conversion devices, such as the solid oxide fuel cells (SOFCs). In this study, the degradation of SOFC anodes by the deposition of potassium compounds (KCl, K2CO3, and KOH) was investigated. An aqueous solution of potassium compounds was dripped onto the anode surface of the SOFC button cell at room temperature. After drying at 343 K, 6.964 × 10-6 mol KCl, 6.964 × 10-6 mol KOH, and 3.482 × 10-6 mol K2CO3 was deposited on the anode. Button cells with the deposition of K compounds were employed for power generation experiments at 1023 K with the supply of artificial syngas from biomass gasification. After the power generation experiments, the surface structures of the anodes were microscopically analyzed using the SEM and EDS. As a result, K compounds hardly affected the OCV of SOFC. With the addition of KCl, no apparent change in the anode structure was observed, and only a slight KCl deposit was detected. However, chloride tends to be chemisorbed on Ni, increasing the ohmic resistance as well as the adsorption/desorption resistance. However, KOH transformed to K2CO3 and then remained massively on the anode, which was clearly observed in the SEM images. K2CO3 significantly decreased the cell voltage under a current density of 100 mA·cm−2. Through impedance analyses, this voltage drop was mainly attributed to the ohmic resistance and gas diffusion resistance. However, there is no evidence that this deposit degrades Ni particles.

Prediction of electrode microstructure evolutions with physically constrained unsupervised image-to-image translation networks

Microstructure of electrodes determines the performance of electrochemical devices such as fuel cells and batteries. The efficiency and economic feasibility of these technologies depend on the stability of the microstructures throughout their lifetime. Although modeling techniques were proposed for determining electrode performance from 2- or 3-dimensional microstructural data, it is still extremely challenging to predict long-term structural degradation by means of numerical simulations. One of the major challenges is to overcome the difficulties in obtaining experimental data of an identical sample through the degradation process. In this work, a machine learning-based framework for predicting microstructural evolutions with limited amount of un-paired training data is proposed. Physically-constrained unsupervised image-to-image translation (UNIT) network is incorporated to predict nickel oxide reduction process in solid oxide fuel cell anode. The proposed framework is firstly validated by simplified toy-problems. Secondly, the UNIT network is applied to real microstructures of solid oxide fuel cells, which results in excellent visual and statistical agreements between real and artificially reduced samples. The proposed network can predict evolutions in new microstructures, which have not been used during training. Furthermore, a conditional UNIT network (C-UNIT) was demonstrated, which can predict the microstructure evolutions based on process conditions as well as continuous time series of microstructural changes.

Direct ammonia SOFC – A potential technology for green shipping

International shipping carries about 90% of the global trade, thereby emitting significant amounts of greenhouse gasses by using fossil based fuels. Zero-emission technologies using green fuels are crucial to reduce the environmental impact of this important transport sector. Among the considered concepts is green ammonia in a solid oxide fuel cell (SOFC).The present study investigated SOFCs fueled with ammonia regarding cracking, electrochemical performance and durability. Ammonia cracking was for the first time directly measured over a planar, anode supported SOFC at open circuit voltage and during operation, as well as in presence of several balance of plant components. At temperatures around 700 °C, ammonia is significantly cracked when passing over hot metallic low surface area components (like Ni current collectors) even in the absence of the SOFC. The Ni/YSZ SOFC anode is active for the cracking as well. The area specific resistance of the SOFC is larger when using ammonia as compared to a H2/N2 mixture, due to two origins, (i) a decrease of the cell temperature due to the endothermal cracking, which leads to larger ohmic resistance and (ii) presence of unconverted ammonia, which increases the polarisation resistance in the low frequency region. Durability tests reveal increased cell voltage degradation when using ammonia fuel at 700 °C, mainly due to increase of the ohmic contributions. Micro structural analysis suggests nitridation as cause of this degradation. A stable SOFC operation is possible at 750 °C.

Mo-Doped LSCF as a Novel Coke-Resistant Anode for Biofuel-Fed SOFC.

Climate change and damage to the environment, as well as the limitations of fossil fuels, have pushed governments to explore infinite renewable energy options such as biofuels. Solid Oxide Fuel Cell (SOFC) is a sustainable energy device that transforms biofuels into power and heat. It is now being researched to function at intermediate temperatures (600-700 °C) in order to prevent material deterioration and improve system life span. However, one of the major disadvantages of reducing the temperature is that carbon deposition impairs the electrochemical performance of the cell with a Ni-YSZ traditional anode. Here, molybdenum was doped into La0.6Sr0.4Co0.2Fe0.8O3-δ (LSCFMo) as an innovative anode material with higher coke resistance and better phase stability under reducing conditions. X-ray diffraction (XRD) analysis showed increasing phase stability by increasing the Mo dopant. Electrochemical measurements proved that the LSCFMo anode is an active catalyst towards the methanol oxidation even at low temperatures as 600 °C, with an open circuit voltage (OCV) of 0.55 V, while GDC10 (Ga0.9Ce0.1O1.95) is used as the electrolyte. As an insightful result, no trace of any carbon deposition was found on the anode side after the tests. The combination of phase composition, morphological, and electrochemical studies demonstrate that LSCFMo is a suitable anode material for SOFCs fed by biofuels.

Influence of the La0.2Sr0.7Ti0.95Ni0.05O3 (LSTN) Synthesis Method on SOFC Anode Performance

Solid oxide fuel cells are characterized by a high efficiency for converting chemical energy into electricity and fuel flexibility. This research work focuses on developing durable and efficient anodes for solid oxide fuel cells (SOFCs) based on exsolving nickel from the perovskite structure. A-site-deficient La- and Ni-doped strontium titanates (La0.2Sr0.7Ti0.95Ni0.05O3−δ, LSTN) were synthesized using four different techniques and mixed with Ce0.8Gd0.2O2−δ (GDC) to form the SOFC anode. The synthesis routes of interest for comparison included solid-state, sol-gel, hydrothermal, and co-precipitation methods. LSTN powders were characterized via XRD, SEM, TPR, BET and XPS. In situ XRD during reduction was measured and the reduced powders were analyzed using TEM. The impact of synthesis route on SOFC performance was investigated. All samples were highly durable when kept at 0.5 V for 48 h at 800 °C with H2 fuel. Interestingly, the best performance was observed for the cell with the LSTN anode prepared via co-precipitation, while the conventional solid-state synthesis method only achieved the second-best results.

Numerical study on the impact of carbon deposition on methane/steam mass transport in solid oxide fuel cell porous anode using lattice Boltzmann modeling

Solid Oxide Fuel Cell (SOFC) is an energy conversion device with high efficiency and cleanliness. However, anode carbon deposition severely affects SOFC performance during reforming with hydrocarbon fuels. In this paper, numerical simulations based on the Lattice Boltzmann (LB) method are used to construct the porous anode structure after carbon deposition by means of the binary dilation method, and the effects of different carbon deposition behaviors on the methane/steam flow behaviors and mass transport in the porous medium of SOFC anode are investigated. The results show that anode carbon deposition decreases the methane/steam mass transfer efficiency, and as the degree of carbon deposition increases, dead pores are formed and gas passage is impeded. This paper investigates the effect of different degrees of carbon deposition behavior on anode gas transport, which can further understand the importance of carbon removal in SOFC anode during the methane reforming reaction.