Publications
95 results found
Westhead O, Spry M, Bagger A, et al., 2023, The role of ion solvation in lithium mediated nitrogen reduction, Journal of Materials Chemistry A, ISSN: 2050-7488
Since its verification in 2019, there have been numerous high-profile papers reporting improved efficiency of lithium-mediated electrochemical nitrogen reduction to make ammonia. However, the literature lacks any coherent investigation systematically linking bulk electrolyte properties to electrochemical performance and Solid Electrolyte Interphase (SEI) properties. In this study, we discover that the salt concentration has a remarkable effect on electrolyte stability: at concentrations of 0.6 M LiClO4 and above the electrode potential is stable for at least 12 hours at an applied current density of −2 mA cm−2 at ambient temperature and pressure. Conversely, at the lower concentrations explored in prior studies, the potential required to maintain a given N2 reduction current increased by 8 V within a period of 1 hour under the same conditions. The behaviour is linked more coordination of the salt anion and cation with increasing salt concentration in the electrolyte observed via Raman spectroscopy. Time of flight secondary ion mass spectrometry and X-ray photoelectron spectroscopy reveal a more inorganic, and therefore more stable, SEI layer is formed with increasing salt concentration. A drop in faradaic efficiency for nitrogen reduction is seen at concentrations higher than 0.6 M LiClO4, which is attributed to a combination of a decrease in nitrogen solubility and diffusivity as well as increased SEI conductivity as measured by electrochemical impedance spectroscopy.
Seymour ID, Quérel E, Brugge RH, et al., 2023, Understanding and Engineering Interfacial Adhesion in Solid-State Batteries with Metallic Anodes., ChemSusChem
High performance alkali metal anode solid-state batteries require solid/solid interfaces with fast ion transfer that are morphologically and chemically stable upon electrochemical cycling. Void formation at the alkali metal/solid-state electrolyte interface during alkali metal stripping is responsible for constriction resistances and hotspots that can facilitate dendrite propagation and failure. Both externally applied pressures (35-400 MPa) and temperatures above the melting point of the alkali metal have been shown to improve the interfacial contact with the solid electrolyte, preventing the formation of voids. However, the extreme pressure and temperature conditions required can be difficult to meet for commercial solid-state battery applications. In this review, we highlight the importance of interfacial adhesion or 'wetting' at alkali metal/solid electrolyte interfaces for achieving solid-state batteries that can withstand high current densities without cell failure. The intrinsically poor adhesion at metal/ceramic interfaces poses fundamental limitations on many inorganics solid-state electrolyte systems in the absence of applied pressure. Suppression of alkali metal voids can only be achieved for systems with high interfacial adhesion (i. e. 'perfect wetting') where the contact angle between the alkali metal and the solid-state electrolyte surface goes to θ=0°. We identify key strategies to improve interfacial adhesion and suppress void formation including the adoption of interlayers, alloy anodes and 3D scaffolds. Computational modeling techniques have been invaluable for understanding the structure, stability and adhesion of solid-state battery interfaces and we provide an overview of key techniques. Although focused on alkali metal solid-state batteries, the fundamental understanding of interfacial adhesion discussed in this review has broader applications across the field of chemistry and material science from corrosion to biomaterials de
Williams NJ, Quérel E, Seymour ID, et al., 2023, Operando characterization and theoretical modeling of metal|electrolyte interphase growth kinetics in solid-state batteries. Part II: Modeling, Chemistry of Materials, Vol: 35, Pages: 863-869, ISSN: 0897-4756
Understanding the interfacial dynamics of batteries is crucial to control degradation and increase electrochemical performance and cycling life. If the chemical potential of a negative electrode material lies outside of the stability window of an electrolyte (either solid or liquid), a decomposition layer (interphase) will form at the interface. To better understand and control degradation at interfaces in batteries, theoretical models describing the rate of formation of these interphases are required. This study focuses on the growth kinetics of the interphase forming between solid electrolytes and metallic negative electrodes in solid-state batteries. More specifically, we demonstrate that the rate of interphase formation and metal plating during charge can be accurately described by adapting the theory of coupled ion-electron transfer (CIET). The model is validated by fitting experimental data presented in the first part of this study. The data was collected operando as a Na metal layer was plated on top of a NaSICON solid electrolyte (Na3.4Zr2Si2.4P0.6O12 or NZSP) inside an XPS chamber. This study highlights the depth of information which can be extracted from this single operando experiment and is widely applicable to other solid-state electrolyte systems.
Quérel E, Williams NJ, Seymour ID, et al., 2023, Operando characterization and theoretical modeling of Metal|Electrolyte interphase growth kinetics in solid-state batteries. Part I: experiments, Chemistry of Materials, Vol: 35, Pages: 853-862, ISSN: 0897-4756
To harness all of the benefits of solid-state battery (SSB) architectures in terms of energy density, their negative electrode should be an alkali metal. However, the high chemical potential of alkali metals makes them prone to reduce most solid electrolytes (SE), resulting in a decomposition layer called an interphase at the metal|SE interface. Quantitative information about the interphase chemical composition and rate of formation is challenging to obtain because the reaction occurs at a buried interface. In this study, a thin layer of Na metal (Na0) is plated on the surface of an SE of the NaSICON family (Na3.4Zr2Si2.4P0.6O12 or NZSP) inside a commercial X-ray photoelectron spectroscopy (XPS) system while continuously analyzing the composition of the interphase operando. We identify the existence of a solid electrolyte interphase at the Na0|NZSP interface, and more importantly, we demonstrate for the first time that this protocol can be used to study the kinetics of interphase formation. A second important outcome of this article is that the surface chemistry of NZSP samples can be tuned to improve their stability against Na0. It is demonstrated by XPS and time-resolved electrochemical impedance spectroscopy (EIS) that a native NaxPOy layer present on the surface of as-sintered NZSP samples protects their surface against decomposition.
Westhead O, Spry M, Bagger A, et al., 2023, The role of ion solvation in lithium mediated nitrogen reduction ( Nov, 10.1039/D2TA07686A, 2022), Journal of Materials Chemistry A, Pages: 1-1, ISSN: 2050-7488
Shih P, Aguadero A, Skinner S, 2023, A-site acceptor-doping strategy to enhance oxygen transport in sodium bismuth titanate perovskite, Journal of the American Ceramic Society, Vol: 106, Pages: 100-108, ISSN: 0002-7820
Sodium–bismuth–titanate (NBT) has recently been shown to contain high levels of oxide ion conductivity. Here we report the effect of A-site monovalent ions, M+ = K+ and Li+, on the electrical conductivity of NBT. The partial replacement of Bi3+ with monovalent ions improved the ionic conductivity by over one order of magnitude without an apparent change of the conduction mechanism, which is attributed to an increase in the oxygen vacancy concentration based on an acceptor-doping approach. The 18O tracer-diffusion coefficient (D*) determined by the isotope exchange depth profile method in combination with secondary ion mass spectrometry confirmed that oxygen ions are the main charge carriers in the system. Among these acceptor-doped samples, 4% Li doping provides the highest total conductivity, leading to a further discussion of doping strategies for NBT-based materials to enhance the electrical behavior, is discussed. Comparisons with other oxide-ion conductors and an oxygen-vacancy diffusivity limit model in perovskite lattice suggested that the doped NBT-based materials might already have achieved the optimization of the ionic conductivity.
Tarancon A, Aguadero A, Pryds N, et al., 2022, Special issue for the 2021 E-MRS Spring Meeting Symposium on Solid State Ionics, SOLID STATE IONICS, Vol: 385, ISSN: 0167-2738
Jolly DS, Melvin DLR, Stephens IDR, et al., 2022, Interfaces between Ceramic and Polymer Electrolytes: A Comparison of Oxide and Sulfide Solid Electrolytes for Hybrid Solid-State Batteries, INORGANICS, Vol: 10
- Author Web Link
- Cite
- Citations: 1
Tang Y, Chiabrera F, Morata A, et al., 2022, Ion Intercalation in Lanthanum Strontium Ferrite for Aqueous Electrochemical Energy Storage Devices, ACS APPLIED MATERIALS & INTERFACES, Vol: 14, Pages: 18486-18497, ISSN: 1944-8244
- Author Web Link
- Cite
- Citations: 1
Aguadero A, Wilson G, Seymour I, et al., 2022, Fast redox kinetics in SrCo1-xSbxO3-δ perovskites for thermochemical energy storage and oxygen separation, Journal of The Electrochemical Society, Vol: 169, ISSN: 0013-4651
The use of perovskite materials for thermochemical energy storage and oxygen separation has been gaining momentum in recent years due to their ability to topotactically exchange large volumes of oxygen, and their chemical and structural flexibility. B-site substituted SrCoO3-δ derivatives have previously been investigated as promising materials for intermediate temperature solid oxide fuel cell cathodes due to the stabilization of a 3 C perovskite structure with high electronic and ionic conductivity that allows large oxygen storage capabilities. Here, antimony-substituted strontium cobalt oxides are investigated and identified as new candidate materials for thermochemical oxygen separation applications. In this work we shed light on the exceptional redox kinetics and cyclability of antimony-substituted variants undergoing oxygen exchange at intermediate temperatures (500 to 800 °C). Through the use of density functional theory and isothermal gas atmosphere switching, we demonstrate how the inductive effect of the more electronegative antimony dopants in the Co position, facilitates the kinetics of metal oxide oxidation, whilst hindering reduction reactions. SrCo0.95Sb0.05O3−δ was identified to isothermally evolve 3.76 cm3 g−1 of oxygen at 500 °C and calculated to produce up to 10.44 cm3 g−1 under temperature-swing reaction configurations aligning with previously reported materials.
Acosta M, Baiutti F, Wang X, et al., 2022, Surface chemistry and porosity engineering through etching reveal ultrafast oxygen reduction kinetics below 400 degrees C in B-site exposed (La,Sr)(Co,Fe)O3 thin-films, JOURNAL OF POWER SOURCES, Vol: 523, ISSN: 0378-7753
Chiabrera F, Baiutti F, Diercks D, et al., 2022, Visualizing local fast ionic conduction pathways in nanocrystalline lanthanum manganite by isotope exchange-atom probe tomography, JOURNAL OF MATERIALS CHEMISTRY A, Vol: 10, Pages: 2228-2234, ISSN: 2050-7488
- Author Web Link
- Cite
- Citations: 1
Roman Acevedo W, Aguirre MH, Ferreyra C, et al., 2022, Optimization of the multi-mem response of topotactic redox La1/2Sr1/2Mn1/2Co1/2O3-x, APL MATERIALS, Vol: 10, ISSN: 2166-532X
- Author Web Link
- Cite
- Citations: 1
Pang M-C, Yang K, Brugge R, et al., 2021, Interactions are important: Linking multi-physics mechanisms to the performance and degradation of solid-state batteries, MATERIALS TODAY, Vol: 49, Pages: 145-183, ISSN: 1369-7021
- Author Web Link
- Cite
- Citations: 28
Querel E, Seymour I, Cavallaro A, et al., 2021, The role of NaSICON surface chemistry in stabilizing fast-charging Na metal solid-state batteries, The Journal of High Energy Physics, Vol: 4, Pages: 1-14, ISSN: 1029-8479
Solid-state batteries (SSBs) with alkali metal anodes hold great promise as energetically dense and safe alternatives to conventional Li-ion cells. Whilst, in principle, SSBs have the additional advantage of offering virtually unlimited plating current densities, fast charges have so far only been achieved through sophisticated interface engineering strategies. With a combination of surface sensitive analysis, we reveal that such sophisticated engineering is not necessary in NaSICON solid electrolytes (Na3.4Zr2Si2.4P0.6O12) since optimised performances can be achieved by simple thermal treatments that allow the thermodynamic stabilization of a nanometric Na3PO4 protective surface layer. The optimized surface chemistry leads to stabilized Na|NZSP interfaces with exceptionally low interface resistances (down to 0.1 Ω cm2 at room temperature) and high tolerance to large plating current densities (up to 10 mA cm−2) even for extended cycling periods of 30 min (corresponding to an areal capacity 5 mAh cm−2). The created Na|NZSP interfaces show great stability with increment of only up to 5 Ω cm2 after four months of cell assembly.
Skinner S, Cavallaro A, Cali E, et al., 2021, Analysis of H2O-induced surface degradation in SrCoO3-derivatives and its impact on redox kinetics, Journal of Materials Chemistry A, Vol: 9, Pages: 24528-24538, ISSN: 2050-7488
Substituted SrCoO3 perovskites have been proposed as promising mixed ionic electronic conductors for a range of applications including intermediate temperature solid oxide fuel cells (IT-SOFCs), electrolysers and thermochemical water splitting reactors for H2 production. In this work we investigate the effect of sample exposure to water in substituted SrCoO3 powders and thin films and correlate it with the degradation of oxygen mobility and kinetics. SrCo0.95Sb0.05O3−δ (SCS) thin films have been deposited on different single crystal substrates by pulsed laser deposition (PLD). After water cleaning and post annealing at 300 °C, the sample surface presented an increase of the SrO-surface species as observed by ex situ X-ray Photoemission Spectroscopy (XPS) analysis. This increase in SrO at the sample surface has also been confirmed by the Low Energy Ion Scattering (LEIS) technique on both SCS thin film and powder. Thermochemical water splitting experiments on SCS and SrCo0.95Mo0.05O3−δ (SCM) powder revealed a phase degradation under water oxidising conditions at high temperature with the formation of the trigonal phase Sr6Co5O15. Transmission Electron Microscopy (TEM) analysis of SCS powder treated with water suggests that this phase degradation could already superficially start at Room Temperature (RT). By isotope exchange depth profile experiments on SCS thin films, we were able to quantify the oxygen diffusivity in this SCS surface decomposed layer (D* = 5.1 × 10−17 cm2 s−1 at 400 °C). In the specific case of bulk powder, the effect of water superficial decomposition translates into a lower oxidation and reduction kinetics as demonstrated by comparative thermogravimetric analysis (TGA) studies.
Baiutti F, Chiabrera F, Diercks D, et al., 2021, Direct Measurement of Oxygen Mass Transport at the Nanoscale, ADVANCED MATERIALS, Vol: 33, ISSN: 0935-9648
- Author Web Link
- Cite
- Citations: 5
Menkin S, O'Keefe CA, Gunnarsdottir AB, et al., 2021, Toward an Understanding of SEI Formation and Lithium Plating on Copper in Anode-Free Batteries, JOURNAL OF PHYSICAL CHEMISTRY C, Vol: 125, Pages: 16719-16732, ISSN: 1932-7447
- Author Web Link
- Cite
- Citations: 23
Lee J, Amari H, Bahri M, et al., 2021, The complex role of aluminium contamination in nickel-rich layered oxide cathodes for lithium-ion batteries, Batteries & Supercaps, Vol: 4, Pages: 1813-1820, ISSN: 2566-6223
A major challenge for lithium-ion batteries based on nickel-rich layered oxide cathodes is capacity fading. While chemo-mechanical degradation and/or structural transformation are widely considered responsible for degradation, a comprehensive understanding of this process is still not complete. For the stable performance of these cathode materials, aluminium (Al) plays a crucial role, not only as a current collector but also as substitutional element for the transition metals in the cathodes and a protective oxide coating (as Al2O3). However, excess Al can be detrimental due to both its redox inactive nature in the cathode and the insulating nature of Al2O3. In this work, we report an analysis of the Al content in two different types of nickel-rich manganese cobalt oxide cathode materials after battery cycling. Our results indicate a significant thickening of Al-containing phases on the surface of the NMC811 electrode. Similar results are observed from commercial batteries (a mixture of NMC532 and LiMn2O4) that were analysed before use and at the end of life, where Al-containing phases were found to increase significantly at surfaces and grain boundaries. Considering the detrimental effects of the excess Al in the nickel-rich cathodes, our observation of increased Al content via battery cycling is believed to bring a new perspective to the ongoing discussions regarding the capacity fading phenomenon of nickel-rich layered oxide materials as part of their complex degradation mechanisms.
Brugge RH, Chater RJ, Kilner JA, et al., 2021, Experimental determination of Li diffusivity in LLZO using isotopic exchange and FIB-SIMS, JOURNAL OF PHYSICS-ENERGY, Vol: 3, ISSN: 2515-7655
- Author Web Link
- Cite
- Citations: 8
Seymour ID, Aguadero A, 2021, Suppressing void formation in all-solid-state batteries: the role of interfacial adhesion on alkali metal vacancy transport, JOURNAL OF MATERIALS CHEMISTRY A, Vol: 9, Pages: 19901-19913, ISSN: 2050-7488
- Author Web Link
- Cite
- Citations: 5
Celorrio V, Tiwari D, Calvillo L, et al., 2021, Electrocatalytic Site Activity Enhancement via Orbital Overlap in A(2)MnRuO(7) (A = Dy3+, Ho3+, and Er3+) Pyrochlore Nanostructures, ACS APPLIED ENERGY MATERIALS, Vol: 4, Pages: 176-185, ISSN: 2574-0962
- Author Web Link
- Cite
- Citations: 6
Skinner S, Aguadero A, Tsai C-Y, 2020, High electrical conductivity and crystal structure of the solid oxide cell electrode Pr4Ni3O10-δ, Journal of Solid State Chemistry, Vol: 289, Pages: 1-9, ISSN: 0022-4596
Pr4Ni3O10-δ is a promising air electrode for solid oxide fuel cells and electrolysers with comparable performance to Pr2NiO4+δ but with improved thermodynamic stability at a cell operating temperature of 600 °C–800 °C. To fully understand and integrate Pr4Ni3O10-δ into commercial devices there are several aspects that remain to be addressed. This study provides a systematic analysis of the synthesis kinetics, crystal structure, oxygen content and electrical conductivity providing clear paths for the development of Pr4Ni3O10-δ-based low temperature solid oxide electrochemical devices with enhanced performance and stability. We prove that the material can reach a remarkable electrical conductivity of 235 Scm-1 at 700 °C in air, much higher than the previously reported values of 86 Scm-1 and 56 Scm-1, rising to 278 Scm-1 at 450 °C. High resolution neutron powder and in-situ X-ray diffraction confirmed that Pr4Ni3O10-δ crystallises in the monoclinic P21/a space group, and that no phase transitions were observed on heating to 1000 °C in air. An electrical conductivity anomaly was found at ~300 °C and is attributed to a subtle change in the local structure of the material, potentially associated with changes in the oxygen content.
Celikbilek O, Cavallaro A, Kerherve G, et al., 2020, Surface restructuring of thin-film electrodes based on thermal history and its significance for the catalytic activity and stability at the gas/solid and solid/solid interfaces, ACS Applied Materials & Interfaces, Vol: 12, Pages: 34388-34401, ISSN: 1944-8244
Electrodes in solid-state energy devices are subjected to a variety of thermal treatments, from film processing to device operation at high temperatures. All these treatments influence the chemical activity and stability of the films, as the thermally induced chemical restructuring shapes the microstructure and the morphology. Here, we investigate the correlation between the oxygen reduction reaction (ORR) activity and thermal history in complex transition metal oxides, in particular, La0.6Sr0.4CoO3−δ (LSC64) thin films deposited by pulsed laser deposition. To this end, three ∼200 nm thick LSC64 films with different processing and thermal histories were studied. A variety of surface-sensitive elemental characterization techniques (i.e., low-energy ion scattering, X-ray photoelectron spectroscopy, and secondary ion mass spectrometry) were employed to thoroughly investigate the cationic distribution from the outermost surface to the film/substrate interface. Moreover, electrochemical impedance spectroscopy was used to study the activity and the stability of the films. Our investigations revealed that, despite the initial comparable ORR activity at 600 °C, the degradation rates of the films differed by twofold in the long-term stability tests at 500 °C. Here, we emphasize the importance of processing and thermal history in the elemental surface distribution, especially for the stability of LSC64 electrodes and propose that they should be considered as among the main pillars in the design of active surfaces.
Brugge RH, Pesci FM, Cavallaro A, et al., 2020, The origin of chemical inhomogeneity in garnet electrolytes and its impact on the electrochemical performance, Journal of Materials Chemistry A, Vol: 8, Pages: 14265-14276, ISSN: 2050-7488
The interface between solid electrolytes and lithium metal electrodes determines the performance of an all-solid-state battery in terms of the ability to demand high power densities and prevent the formation of lithium dendrites. This interface depends strongly on the nature of the solid electrolyte surface in contact with the metallic anode. In the garnet electrolyte/Li system, most papers have focused on the role of current inhomogeneities induced by void formation in the Li metal electrode and the presence of insulating reaction layers following air exposure. However, extended defects in the solid electrolyte induced by chemical and/or structural inhomogeneities can also lead to uneven current distribution, impacting the performance of these systems. In this work, we use complementary surface analysis techniques with varying analysis depths to probe chemical distribution within grains and grain boundaries at the surface and in the bulk of garnet-type electrolytes to explain their electrochemical performance. We show that morphology, post-treatments and storage conditions can greatly affect the surface chemical distribution of grains and grain boundaries. These properties are important to understand since they will dictate the ionic and electronic transport near the interfacial zone between metal and electrolyte which is key to determining chemo-mechanical stability.
Pesci FM, Bertei A, Brugge RH, et al., 2020, Establishing ultra-low activation energies for lithium transport in garnet electrolytes., ACS Applied Materials and Interfaces, Vol: 12, Pages: 32086-32816, ISSN: 1944-8244
Garnet-type structured lithium ion conducting ceramics represent a promising alternative to liquid-based electrolytes for all-solid-state batteries. However, their performance is limited by their polycrystalline nature and the inherent inhomogeneous current distribution due to the different ion dynamics at grains, grain boundaries and interfaces. In this study we use a combination of electrochemical impedance spectroscopy, distribution of relaxation times analysis and solid state nuclear magnetic resonance (NMR), in order to understand the role that bulk, grain boundary and interfacial processes play in the ionic transport and electrochemical performance of garnet based cells. Variable temperature impedance analysis reveals the lowest activation energy (Ea) for Li transport in the bulk of the garnet electrolyte (0.15 eV), consistent with pulsed field gradient NMR spectroscopy measurements (0.14 eV). We also show a decrease in grain boundary activation energy at temperatures below 0 °C, that is followed by the total conductivity, suggesting that the bottleneck to ionic transport resides in the grain boundaries. We reveal that the grain boundary activation energy is heavily affected by its composition that, in turn, is mainly affected by the segregation of dopants and Li. We suggest that by controlling the grain boundary composition, it would be possible to pave the way towards targeted engineering of garnet-type electrolytes and ameliorate their electrochemical performance in order to enable their use in commercial devices.
Roman Acevedo W, van den Bosch CAM, Aguirre MH, et al., 2020, Large memcapacitance and memristance at Nb:SrTiO3/La0.5Sr0.5Mn0.5Co0.5O3-delta topotactic redox interface (vol 116, 063502, 2020), APPLIED PHYSICS LETTERS, Vol: 116, ISSN: 0003-6951
Roman Acevedo W, van den Bosch CAM, Aguirre MH, et al., 2020, Large memcapacitance and memristance at Nb:SrTiO3/La0.5Sr0.5Mn0.5Co0.5O3-delta topotactic redox interface, APPLIED PHYSICS LETTERS, Vol: 116, ISSN: 0003-6951
- Author Web Link
- Cite
- Citations: 3
van den Bosch C, Cavallaro A, Moreno R, et al., 2020, Revealing strain effects on the chemical compositionof Perovskite oxide thin films surface, bulk, and interfaces, Advanced Materials Interfaces, Vol: 7, ISSN: 2196-7350
Understanding the effects of lattice strain on oxygen surface and diffusion kinetics in oxides is a controversial subject that is critical for developing efficient energy storage and conversion materials. In this work, high-quality epitaxial thin films of the model perovskite La0.5Sr0.5Mn0.5Co0.5O3-δ (LSMC), under compressive or tensile strain, were characterized with a combination of in situ and ex situ bulk and surface-sensitive techniques. The results demonstrate a non-linear correlation of mechanical and chemical properties as a function of the operation conditions. It was observed that the effect of strain on reducibility is dependent on the “effective strain” induced on the chemical bonds. In plain strain, and in particular the relative B-O length bond, are the key factor controlling which of the B-site cation would be reduced preferentially. Furthermore, the need to use a set of complimentary techniques to isolate different chemically-induced strain effects was proven. With this, it was confirmed that tensile strain favors the stabilization of a more reduced lattice, accompanied by greater segregation of strontium secondary phases and a decrease of oxygen exchange kinetics on LSMC thin films.
Tsai C-Y, McGilvery CM, Aguadero A, et al., 2019, Phase evolution and reactivity of Pr2NiO4+δ and Ce0.9Gd0.1O2-δ composites under solid oxide cell sintering and operation temperatures, International Journal of Hydrogen Energy, Vol: 44, Pages: 31458-31465, ISSN: 0360-3199
In developing a new compositae air electrode for Solid Oxide Cells (SOCs) it is essential to fully understand the phase chemistry of all components. Ruddlesden-Popper type electrodes such as Pr2NiO4+δ have previously been proposed as attractive alternatives to conventional La0·6Sr0·4Fe0·8Co0·2O3-δ/Ce1-xGdxO2-δ compositae air electrodes for both fuel cell and electrolyser modes of operation. However, Pr2NiO4+δ have been shown to have limited stability, reacting with a Ce1-xGdxO2-δ interlayer to form a Ce1-x-yGdxPryO2-δ (CGPO) phase of unknown stoichiometry. Additionally, Pr2NiO4+δ are known to decompose to Pr4Ni3O10 ± δ under certain conditions.In this work detailed understanding of the chemical reaction between Pr2NiO4+δ and Ce0.9Gd0.1O2-δ (CGO10) under normal solid oxide cell fabrication and operating temperatures was obtained, identifying the composition of the resulting CGPO phase reaction products. It is shown that, in addition to the unreacted CGO10 present after sintering the compositae at 1100 °C for up to 12 h, a series of CGPO chemical compositions were formed with various Ce, Gd and Pr ratios depending on the relative distance of the doped ceria phases from the Pr2NiO4+δ phases. The extent of the chemical reaction was found to depend on the sintering time and the contact area of the two phases. Further thermal treatment of the resulting products under SOC air electrode operating temperature (800 °C) resulted in the initiation of Pr2NiO4+δ decomposition, forming Pr4Ni3O10 ± δ and Pr6O11 with no detectable change in the composition of previously formed Pr-substituted ceria phases. It is apparent that the Pr2NiO4+δ/CGO10 compositae is unsuitable as an air electrode, but there is evidence that the decomposition products, Pr4Ni3O10 ± δ and Ce1-x-yGdxPryO2-δ are stable and suitable candidates for SOC electrodes.
This data is extracted from the Web of Science and reproduced under a licence from Thomson Reuters. You may not copy or re-distribute this data in whole or in part without the written consent of the Science business of Thomson Reuters.