Ceramic Anode Research Articles

Effect of Samaria Doped Ceria Impregnation on the Electrochemical Performance of Strontium Doped Lanthanum Chromium Manganite Anode for Solid Oxide Fuel Cells

Strontium doped lanthanum chromium manganite (LSCM) is a potential ceramic anode material for next-generation hydrocarbon-fueled solid oxide fuel cells. Because of its relatively low electrochemical performance, however, its application is still limited. This work investigated the effect of samaria-doped ceria (SDC) impregnation on the electrode performance regarding the surface reaction and oxygen-ion transport in the electrode reaction. The results showed that the electrochemical performance had been promoted by incorporating with nano-SDC particles. Electrical conductivity relaxation (ECR) of dense LSCM exhibited significant improvement in the surface exchange coefficient, from 5.34 × 10−6 cm s−1 at 850°C for bare LSCM to 1.48 × 10−4 cm s−1 for LSCM coated with 0.9 mol L−1 SDC precursor solution. The surface reaction promotion factor was about 28 for the nano SDC particle coating, much higher than the factor of 6.5 for LSCM-SDC composite. It was demonstrated that the promotion in surface reaction rate are mainly contributed by LSCM-SDC-gas three-phase boundaries (3PB). Interfacial polarization resistances of SDC impregnated LSCM symmetrical cells presented over 1 order of magnitude reduction at 850°C with a SDC loading of 35.8 wt%. The electrode performance improvement was attributed to the connective oxygen ion conduction path and increased 3PB formed by the impregnated SDC particles.

Structural investigation of electrochemically active ceramic anodes for next-generation solid oxide fuel cells (SOFCs) and solid oxide electrolysis cells (SOECs)

Structural investigation of electrochemically active ceramic anodes for next-generation solid oxide fuel cells (SOFCs) and solid oxide electrolysis cells (SOECs)

Tin doped PrBaFe2O5+δ anode material for solid oxide fuel cells

PrBaFe1.9Sn0.1O5+δ shows excellent redox stability, high electrical conductivity, and ASR of a symmetrical cell as low as of 0.095–0.285 Ω cm2 from 850–750 °C in wet hydrogen, better than or comparable to the best of ceramic anodes in the open literature.

Sub-stoichiometric titanium oxide (Ti4O7) as a suitable ceramic anode for electrooxidation of organic pollutants: A case study of kinetics, mineralization and toxicity assessment of amoxicillin

Electrochemical degradation of aqueous solutions containing antibiotic amoxicillin (AMX) has been extensively studied in an undivided electrolytic cell using a sub-stoichiometric titanium oxide (Ti4O7) anode, elaborated by plasma deposition. Oxidative degradation of AMX by hydroxyl radicals was assessed as a function of applied current and was found to follow pseudo-first order kinetics. The use of carbon-felt cathode enhanced oxidation capacity of the process due to the generation of H2O2. Comparative studies at low current intensity using dimensional stable anode (DSA) and Pt anodes led to the lower mineralization efficiencies compared to Ti4O7 anode: 36 and 41% TOC removal for DSA and Pt respectively compared to 69% for Ti4O7 anode. Besides, the use of boron doped diamond (BDD) anode under similar operating conditions allowed reaching higher mineralization (94%) efficiency. Although Ti4O7 anode provides a lesser mineralization rate compared to BDD, it exhibits better performance compared to the classical anodes Pt and DSA and can constitutes an alternative to BDD anode for a cost effective electro-oxidation process. Moreover several aromatic and aliphatic oxidation reaction intermediates and inorganic end-products were identified and a plausible mineralization pathway of AMX involving these intermediates was proposed.

Hodrogen Oxidation Reaction Mechanisms in Mixed Ionic and Electronic Conducting Oxide Anode for Solid Oxide Fuel Cells

Ceramics anode offers certain advantages in terms of impurity tolerance and other properties, as compared to conventional Ni/YSZ anode for solid oxide fuel cells (SOFC). However, ceramic anodes typically have much lower electrochemical performance, and there is very few studies on the hydrogen oxidation reaction (HOR) mechanisms and kinetics in ceramic anodes. In this research, using Doped YCrO3 as baseline material, we systematically investigated the HOR mechanisms in mixed ionic and electronic conducting (MIEC) ceramic anodes, with the focus on the effect of electronic conductivity, electro-catalytic activity, triple-phase-boundary (3PB), and electrolyte, on the HOR kinetics. It is found that both electrical conductivity and electrode performance of yttrium chromites have been enhanced after Co and Ni doping. Electrochemical impedance spectroscopy (EIS) results indicate that charge transfer process at high frequency and surface adsorption/diffusion processes at low frequency domain can be the dominant anode reaction steps. Ni doping accelerates the surface processes by reducing the related activation energy from 1.2 to 0.5 eV. It also substantially improves the charge transfer process probably by increasing the amount of adsorbed H on electrode surface. The resistance of high frequency is found to be dependent on H2 content. The observed reaction order is 1/4 for Co doped and 1/3 ~ 1/2 for Ni doped yttrium chromites. A model of H2oxidation reaction is proposed, revealing this dependence stems from the reaction between adsorbed H and the lattice oxygen. The influence of electrolyte to electrode performance was investigated by replacing YSZ electrolyte with scandium stabilized zirconium (SSZ). Smaller polarization resistances are observed on each electrode in both wet H2 and air atmospheres. Replacement of electrolyte can alter not only the rate of charge transfer process but also in some cases other surface processes not related to the electrolyte directly. It is proposed that the impact of the electrolyte on each electrode process is passed down as in a chain and the charge transfer step functions as the first ring in the chain.

Robust SOFC anode materials with La-doped SrTiO3 backbone structure

Redox-stable Sr0.9La0.1TiO3 (SLT) with Ce0.9Gd0.1O2 (GDC) and (Sc2O3)0.1(CeO2)0.01(ZrO2)0.89 (SSZ) was used to fabricate robust anodes for zirconia-based electrolyte-supported SOFCs. The anode consisted of three layers: a layer of 60wt% GDC-40wt% SLT or 40wt% SSZ-60wt% SLT as a functional layer and two layers of SLT as current conducting layers. An impregnation method has been employed to decorate nano-sized Ni and CeO2 into the ceramic anode to improve electrochemical performance and redox stability. It was found that the catalyst impregnated ceramic anode has improved redox stability compared with the conventional Ni-SSZ cermet. The incorporation of the oxide catalyst, CeO2, during co-impregnation process was found to even further improve redox stability of the anode, since CeO2 particles have a lower tendency to aggregate during redox cycling.

High-Performance Anode Material Sr2FeMo0.65Ni0.35O6-δ with In Situ Exsolved Nanoparticle Catalyst.

A metallic nanoparticle-decorated ceramic anode was prepared by in situ reduction of the perovskite Sr2FeMo0.65Ni0.35O6-δ (SFMNi) in H2 at 850 °C. The reduction converts the pure perovksite phase into mixed phases containing the Ruddlesden-Popper structure Sr3FeMoO7-δ, perovskite Sr(FeMo)O3-δ, and the FeNi3 bimetallic alloy nanoparticle catalyst. The electrochemical performance of the SFMNi ceramic anode is greatly enhanced by the in situ exsolved Fe-Ni alloy nanoparticle catalysts that are homogeneously distributed on the ceramic backbone surface. The maximum power densities of the La0.8Sr0.2Ga0.8Mg0.2O3-δ electrolyte supported a single cell with SFMNi as the anode reached 590, 793, and 960 mW cm(-2) in wet H2 at 750, 800, and 850 °C, respectively. The Sr2FeMo0.65Ni0.35O6-δ anode also shows excellent structural stability and good coking resistance in wet CH4. The prepared SFMNi material is a promising high-performance anode for solid oxide fuel cells.

Interface‐Engineered All‐Solid‐State Li‐Ion Batteries Based on Garnet‐Type Fast Li+ Conductors

All‐solid‐state Li‐ion batteries based on Li7La3Zr2O12 (LLZO) garnet structures require novel electrode assembly strategies to guarantee a proper Li+ transfer at the electrode–electrolyte interfaces. Here, first stable cell performances are reported for Li‐garnet, c‐Li6.25Al0.25La3Zr2O12, all‐solid‐state batteries running safely with a full ceramics setup, exemplified with the anode material Li4Ti5O12. Novel strategies to design an enhanced Li+ transfer at the electrode–electrolyte interface using an interface‐engineered all‐solid‐state battery cell based on a porous garnet electrolyte interface structure, in which the electrode material is intimately embedded, are presented. The results presented here show for the first time that all‐solid‐state Li‐ion batteries with LLZO electrolytes can be reversibly charge–discharge cycled also in the low potential ranges (≈1.5 V) for combinations with a ceramic anode material. Through a model experiment, the interface between the electrode and electrolyte constituents is systematically modified revealing that the interface engineering helps to improve delivered capacities and cycling properties of the all‐solid‐state Li‐ion batteries based on garnet‐type cubic LLZO structures.

A new concept of ceramic consumable anode for iron pyroelectrolysis in magnesium aluminosilicate melts

Driven by environmental challenges and global movement to carbon-lean technologies, the pyroelectrolysis process for iron extraction from oxide melts is being proposed as an interesting alternative to the traditional steelmaking. Still, one of the critical issues impacting the prospects of this technology includes the development of appropriate anode materials, taking into account the extremely aggressive nature of oxide melts at very high temperatures. Here we propose a unique concept of consumable anode for pyroelectrolysis process, based on multicomponent ferrospinel-based ceramics. The electrochemical studies and post-mortem XRD/SEM/EDS analysis of the electrolysis cells have demonstrated that ceramic spinel anodes can sustain significant current densities for making the process feasible, while their consumption by interaction with Si-containing species from the molten electrolyte was found to be moderate.

Layered Perovskite Electrodes with High Performance and Durability for Solid Oxide Electrolysis

In recently years, there has been a robust attention in clean and renewable energy sources due to heavy dependence on finite fossil fuels as our major source of energy, causing serious energy and environmental crisis such as emission of CO2 and NO x on the world. Hydrogen is attracted as a leading candidate for alternative future fuels because it has the potential to address the environmental and energy security issues associated with fossil hydrocarbon fuels. Solid oxide electrolysis cells (SOECs) are one of the promising technology for the efficient production of H2 from electricity because electrolysis at elevated temperatures is beneficial for both thermodynamic and kinetic reasons. Recent significant interest in steam electrolysis has been mainly concerned with performance, durability and degradation issues. In conventional SOE used for steam electrolysis, the most commonly used cathode and anode materials for oxide ion-conducting SOECs are Ni-YSZ (yttria-stabilized zirconia) and LSM (strontium-doped lanthanum manganites)-YSZ, respectively. But, these electrode materials suffer from several problems such as an intrinsic redox instability, agglomeration and coarsening of nickel particles for Ni-YSZ and a delamination and insufficient durability of LSM-YSZ during steam electrolysis. In this study, the layered perovskite oxides employed as potential ceramic cathode and anode for SOEC with dense LaGaO3 based electrolyte, showing a high performance and durability over 600 hours with no degradation in electrolysis mode.

Electrochemical Performance and Stability of Perovskite Structured Anode Materials for Intermediate Temperature-Solid Oxide Fuel Cells

Solid oxide fuel cells (SOFCs) are highly promising energy conversion devices that can directly convert chemical energy in a fuel to electrical energy. Because they have numerous advantages, such as high conversion efficiency, low pollutant output, and great fuel flexibility, SOFCs have been considered as next-generation clean energy generators.Currently the state of the art anode material for SOFCs is Ni-YSZ cermet. This materials show excellent catalytic activity and stability for the H2 oxidation of hydrogen fuel at SOFC operation conditions. However, Ni-YSZ based anode cermets have a number of drawbacks in system where hydrocarbon fuel is used, such as carbon deposition and sulfur poisoning. In addition, Ni-based anodes suffer from instability upon redox cycling due to the volume expansion of the anode by the Ni oxidation to NiO. This drawbacks of Ni-YSZ cermet significantly may reduces the SOFC lifetime.To overcome these drawbacks of Ni-YSZ based anode, we investigate Ni-free ceramic oxide material as alternative anodes. Developments of Ni-free anode, such as ceria, titanate and lanthanum chromite-based oxides, are required to meet various properties such as high electrochemical performances, tolerance to formation of carbon coking, thermal and redox stability. Among these materials, perovskite-structured materials have been explored to replace Ni-based cermet for SOFCs because they have high tolerance against the carbon deposition and sulfur poisoning with good electrocatalytic performances. In this work, hence we investigate the performance and durability of Ni-free ceramic-based anode during redox cycles of IT-SOFCs. In addition, various transition metals are doped to cramic-based oxide materials to improve electrocatalytic activity, thus resulting in improving the SOFC performance. After the durability testing of SOFCs, electrochemical properties and physicochemical properties of Ni-free ceramic anode cells are investigate by using various analytic techniques such as EIS, SEM, TEM, and XRD.

Chemical Stability of Conductive Ceramic Anodes in LiCl–Li 2 O Molten Salt for Electrolytic Reduction in Pyroprocessing

Conductive ceramics are being developed to replace current Pt anodes in the electrolytic reduction of spent oxide fuels in pyroprocessing. While several conductive ceramics have shown promising electrochemical properties in small-scale experiments, their long-term stabilities have not yet been investigated. In this study, the chemical stability of conductive La 0.33 Sr 0.67 MnO₃ in LiCl-Li₂O molten salt at 650℃ was investigated to examine its feasibility as an anode material. Dissolution of Sr at the anode surface led to structural collapse, thereby indicating that the life time of the La 0.33 Sr 0.67 MnO₃ anode is limited. The dissolution rate of Sr is likely to be influenced by the local environment around Sr in the perovskite framework.

Charge Transfer in Ceramic Anode for Solid Oxide Fuel Cell

Charge Transfer in Ceramic Anode for Solid Oxide Fuel Cell

An investigation of anode and cathode materials in photomicrobial fuel cells.

Photomicrobial fuel cells (p-MFCs) are devices that use photosynthetic organisms (such as cyanobacteria or algae) to turn light energy into electrical energy. In a p-MFC, the anode accepts electrons from microorganisms that are either growing directly on the anode surface (biofilm) or are free floating in solution (planktonic). The nature of both the anode and cathode material is critical for device efficiency. An ideal anode is biocompatible and facilitates direct electron transfer from the microorganisms, with no need for an electron mediator. For a p-MFC, there is the additional requirement that the anode should not prevent light from perfusing through the photosynthetic cells. The cathode should facilitate the rapid reaction of protons and oxygen to form water so as not to rate limit the device. In this paper, we first review the range of anode and cathode materials currently used in p-MFCs. We then present our own data comparing cathode materials in a p-MFC and our first results using porous ceramic anodes in a mediator-free p-MFC.

Microstructural finite element modeling of redox behavior of Ni–YSZ based ceramic SOFC anodes

One of the main challenges in solid oxide fuel cell (SOFC) is the redox problem of Ni-based anodes. Therefore, the redox tolerance of the anode should be improved to increase the service life of the system. Since the real SOFC anodes have a heterogeneous structure with different grain sizes, a micro-level modeling is necessary. Especially, the re-oxidation step which creates large amount of stress is critical during the redox cycles. Therefore, in this study, the effects of re-oxidation temperatures and exposure times on the oxidation rate and stresses developed are investigated on a synthetically generated porous anode functional layer microstructure. A mathematical model is developed to characterize the re-oxidation process and solved numerically. The results indicate that the re-oxidation strongly depends on the re-oxidation temperature and exposure time. The time required for the full oxidation is found to be 7458.55, 313.14, 200.8 and 33.78s at 800, 850, 900 and 950°C, respectively for the generated anode microstructure. In addition, the created stresses in the anode structure are well above the critical material limits.

Influence of Treatment Temperature on Microstructure and Properties of YSZ-NiO Anode Materials.

The cyclic treatment technique (redox cycling) comprising stages of material exposition in reducing and oxidizing high-temperature environments and intermediate degassing between these stages has been developed to improve the structural integrity of YSZ–NiO ceramic anode substrates for solid oxide fuel cells. A series of specimens were singly reduced in a hydrogenous environment (the Ar–5 vol% Н2 mixture or hydrogen of 99.99 vol% H2 purity) under the pressure of 0.15 MPa or subjected to redox cycling at 600 or 800 °C. The influence of redox cycling at the treatment temperatures of 600 and 800 °C on the structure, strength and electrical conductivity of the material has been analysed. Using the treatment temperature 600 °C, a structure providing improved physical and mechanical properties of the material was formed. However, at the treatment temperature 800 °C, an anode structure with an array of microcracks was formed that significantly reduced the strength and electrical conductivity of the material.

A High Performance Ni-Free Redox Reversible Ceramic Anode R-La0.5Sr0.5Fe0.8Cu0.1Ti0.1O3-δ for Intermediate Temperature Solid Oxide Fuel Cells

Ni-free redox reversible perovskite oxide La0.5Sr0.5Fe0.8Cu0.1Ti0.1O3-δ (LSFCT) has been synthesized and in-situ reduced to a functional anode R-LSFCT for intermediate temperature solid oxide fuel cells (ITSOFC). Power generating properties of the cells in various fuels, and the stability of the cell in H2 are investigated by using scandia-stabilized ZrO2 electrolyte and Pr0.5Sr0.5Fe0.8Cu0.2O3-δ cathode. It is found that reasonably high power densities are achieved on the cells with various fuels. The maximum power density (MPD) of the cell with wet H2 as fuel is achieved for values of 690, 531 and 368 mW cm−2 at 800, 750 and 700°C, respectively, and the MPDs of the cells in H2 containing 54 ppm H2S and wet syngas (H2 + 50% CO) fuels are achieved 618 and 512 mW cm−2 at 800°C, respectively. Moreover, the cell in wet H2 demonstrates a quite stable output at 800°C under 0.7 V for 100 h without any decrease. This work also shows that doping Ti stabilizes the perovskite structure of LSFCT in 5% H2-Ar and suppresses the segregation of Sr at surface of LSFCT/R-LSFCT, which may account for the improved cell performance and stability comparing with the undoped R-La0.5Sr0.5Fe0.8Cu0.2O3-δ anode.

Macroporous monolithic Magnéli-phase titanium suboxides as anode material for effective bioelectricity generation in microbial fuel cells

Macroporous monolithic Magnéli-phase titanium suboxides promote bioelectricity generation of microbial fuel cell.

A High-Performing Sulfur-Tolerant and Redox-Stable Layered Perovskite Anode for Direct Hydrocarbon Solid Oxide Fuel Cells.

Development of alternative ceramic oxide anode materials is a key step for direct hydrocarbon solid oxide fuel cells (SOFCs). Several lanthanide based layered perovskite-structured oxides demonstrate outstanding oxygen diffusion rate, favorable electronic conductivity, and good oxygen surface exchange kinetics, owing to A-site ordered structure in which lanthanide and alkali-earth ions occupy alternate (001) layers and oxygen vacancies are mainly located in [LnOx] planes. Here we report a nickel-free cation deficient layered perovskite, (PrBa)0.95(Fe0.9Mo0.1)2O5 + δ (PBFM), for SOFC anode, and this anode shows an outstanding performance with high resistance against both carbon build-up and sulfur poisoning in hydrocarbon fuels. At 800 °C, the layered PBFM showed high electrical conductivity of 59.2 S cm−1 in 5% H2 and peak power densities of 1.72 and 0.54 W cm−2 using H2 and CH4 as fuel, respectively. The cell exhibits a very stable performance under a constant current load of 1.0 A cm−2. To our best knowledge, this is the highest performance of ceramic anodes operated in methane. In addition, the anode is structurally stable at various fuel and temperature conditions, suggesting that it is a feasible material candidate for high-performing SOFC anode.

Fabrication and Characterization of CuxCe1-xO2-δ Nanostructured Anode Material for SOFC Applications by using Mechanochemical Technique

Solid oxide fuel cell (SOFC) works by converting chemical energy into electrical energy due to reforming, and it is one of the promising alternative sources of energy for the future. In the present work, emphasis was given on increasing the electronic conductivity of anode material for SOFC. The Cu0.5Ce0.5O2-δ was prepared by mechanochemical (ball milling) route, with and without pore former. The effect of pore former on the electrical and structural characterization was studied in detail, and found that the Cu0.5Ce0.5O2-δ ceramic anode prepared by using pore former is more effective from structural and electrical points of view. The crystallite size is 58 nanoscales and DC conductivity after reduction is 9.50 ×10-1 Scm-2. Thus, the Cu0.5Ce0.5O2-δ prepared by ball milling using pore former technique could be an emerging potential anode material for SOFC.