bluuebunny/crossref_metadata_2025_split huggingface dataset:
(Invited) Mixed Ionic Electronic Conductors (MIECs): The Importance of Fast and Slow Processes
Authors: Kilner John Anthony 
Published: February 2024

MIECs are ideal materials for use as electrodes in solid state ionic devices. They have found application in SOFCs, SOECs, and solid state battery devices. In this contribution we will focus on MIEC used in the SOFC/SOEC where oxygen is the mobile ion. Most of these materials are complex perovskite materials, for example La1-xSrxCoyFe1-yO3-δ (LSCF). The focus of experimental observation in these materials has been on the fast process of transport of the highly mobile oxygen ion and much is known about the effect of non-stoichiometry in determining the level of oxygen ion transport. Most of these materials are very good mixed conductors at temperatures above 600°C but the lattice oxygen transport drops off markedly at lower temperatures. Recently there have been attempts to improve the lower temperature behaviour by producing nanomaterials, usually in thin film form [1-3], with a high density of grain boundaries. These have been shown to introduce fast diffusion paths along the grain boundaries and have been shown to improve the electrochemical performance.
What has been neglected in the study of these materials is the evolution of the cation distribution in these complex oxides. The cation distribution has a marked effect upon the performance of an MIEC electrode, for example, the segregation of Sr to the surface which is detrimental to the oxygen exchange [4, 5], the development of defect clusters which can trap the oxygen vacancies, and the local chemistry of the grain boundaries [6], affecting transport in polycrystalline materials. Cation transport is a slow process but has importance during the short times and high temperatures during processing, and even more relevantly for the low temperatures but very long times associated with operation. This has implications for the durability of these devices. The contrast between these fast and slow processes will be discussed in this contribution and their relevance to different processing regimes and operational durability.
References
[1] A.M. Saranya, A. Morata, D. Pla, M. Burriel, F. Chiabrera, I. Garbayo, A. Hornes, J.A. Kilner, A. Tarancon, Chemistry of Materials
30 (2018) (16) 5621.
[2] A.M. Saranya, D. Pla, A. Morata, A. Cavallaro, J. Canales-Vázquez, J.A. Kilner, M. Burriel, A. Tarancón, Advanced Energy Materials
5 (2015) (11) 1500377.
[3] E. Navickas, T.M. Huber, Y. Chen, W. Hetaba, G. Holzlechner, G. Rupp, M. Stoger-Pollach, G. Friedbacher, H. Hutter, B. Yildiz, J. Fleig, Physical Chemistry Chemical Physics
17 (2015) (12) 7659.
[4] M. Kubicek, G.M. Rupp, S. Huber, A. Penn, A.K. Opitz, J. Bernardi, M. Stoger-Pollach, H. Hutter, J. Fleig, Phys Chem Chem Phys
16 (2014) (6) 2715.
[5] G.M. Rupp, H. Téllez, J. Druce, A. Limbeck, T. Ishihara, J. Kilner, J. Fleig, Journal of Materials Chemistry A
3 (2015) (45) 22759.
[6] M. Acosta, F. Baiutti, A. Tarancón, J.L. MacManus-Driscoll, Advanced Materials Interfaces
6 (2019) (15) 1900462.
(Invited) Proton Surface Exchange Kinetics and Stability of Thin-Film Triple Conducting Oxides for Protonic Ceramic Electrolysis Cells
Authors: Lee Jongmin , Buckner Haley H , Perry Nicola H. 
Published: February 2024

Protonic ceramic electrolysis cells (PCECs) have been attracting attention due to their ability to operate in the intermediate temperature (300 - 500 ˚C) sweet-spot. These temperatures enable fast kinetics, inexpensive materials (no precious metals; stainless interconnects), and lower operating voltage for producing green hydrogen, without the accelerated degradation that may be observed at higher temperatures. The steam electrodes often support triple conduction and thereby host the proton exchange / oxygen evolution process at the surface, where steam is split. Steam electrode materials development is at a relatively early stage, with open questions around the relationships among bulk composition, evolving surface chemistry, kinetic quantities, and degradation mechanisms. We are investigating the proton exchange surface coefficient (k) and its evolution over time on model thin film electrodes in order to ultimately develop highly active and long-term stable steam electrodes for PCECs.
ABO3 perovskites with Ba on the A-site and nominally multivalent ions on the B-site are candidates for steam electrodes given the varied compositions in this class that can transport oxide ions, protons, and electronic species, and the lowering of hydration enthalpies by the basicity introduced by Ba. However, very few measurements of k exist for these materials, and the evolution of surface chemistry and thus k is poorly understood.
In this work, we fabricated and compared two perovskite triple conducting oxides by growing geometrically well-defined films of Ba(Pr,Y)O3-x (BPY) and Ba(Co,Fe,Zr,Y)O3-x (BCFZY) with pulsed laser deposition. We examined the proton surface exchange coefficients (k-values) using simultaneous in-situ optical transmission relaxation and electrical conductivity relaxation measurements upon switching pH2O at a temperature of 400 ˚C, and continued these switches as a function of time to assess stability. To our knowledge, this is the first use of an optical transmission method to probe elevated temperature steam splitting kinetics, and we interpret the optical (and electrical) changes as indicative of redox during the hydrogenation process. The k-values of BPY thin films were approximately ten times higher than those of the BCFZY thin films, and BPY also retained higher k-values over time. The bulk and surface chemical compositions of BPY and BCFZY thin films before and after relaxation measurements were compared using Rutherford backscattering spectrometry, angle-resolved X-ray photoelectron spectroscopy, and scanning transmission electron microscopy with spectroscopy. Pronounced Ba enrichment and Si contamination (from the quartz tube) were evident at the surface of BPY by both S/TEM-EDS and XPS, whereas for BCFZY these surface chemical features were only detectable by XPS and absent in S/TEM-EDS. Implications for materials design of steam electrodes will be discussed, considering efficiency and lifetime.
High Performance Protonic Ceramic Electrochemical Cells Operating at <500°C
Authors: Liu Fan , Deng Hao , Liu Bin , Duan Chuancheng 
Published: February 2024

Protonic ceramic electrochemical cells (PCECs) can operate in both fuel cell and steam electrolysis modes for efficient power generation and green hydrogen production. Thanks to the low activation energy of proton conduction, PCECs are uniquely capable of operating at temperatures below 600°C. Although some intriguing demonstrations of intermediate-temperature (500-600°C) PCECs (IT-PCECs) have been made in the last decade, the operating temperature of PCECs is still too high to revolutionize ceramic electrochemical cell technology, which is ascribed to the high ohmic resistance and positive electrode polarization resistance. It has been also recognized the electrode polarization resistance dominates the total resistance at <500°C. These challenges suggest both the electrolyte and positive electrode should be redesigned to lower the PCEC operating temperature.
In this work, we present two main approaches to reducing electrolyte ohmic resistance, electrolyte-positive electrode contact resistance, and electrode polarization resistance, which enables PCECs operation at <500°C. First, by using the ultrasonic spray coating system to coat the electrolyte layer on a negative electrode substrate with low Ba-deficiency, a bamboo-structured, ultrathin, and chemically homogeneous electrolyte can be fabricated. Second, a newly in-situ formed composite positive electrode was developed, which enhances the interfacial bonding between the positive electrode and electrolyte, further reducing ASRo

, while improving both bulk oxygen-ion diffusion coefficient and surface oxygen exchange coefficientat <500°C.
The newly developed LT-PCECs attain outstanding power densities in fuel cell mode (as high as 0.77 W cm-2 at 450°C), and exceptional current densities in electrolysis mode (over -1.28 A cm-2 at 1.4 V and 450°C). Furthermore, reducing the temperature does not sacrifice the fuel flexibility of these ceramic fuel cells. We demonstrated that the PCECs can directly utilize ammonia and methane for power generation at <500°C. Exceptional durability has been also demonstrated in both fuel cell and electrolysis modes at <500°C.
These results further emphasize that through the PCEC scalable manufacturing processes and novel positive electrode materials presented here, PCECs can be employed for power generation and H2 production at <500°C, thereby transforming the architectures and removing previous operational constraints of ceramic electrochemical cells for scaled operation. PCECs can therefore be considered as one part of the growing hydrogen economy, while leveraging the existing fossil fuel infrastructure and achieving higher energy efficiency and lower CO2 emissions.
(Invited) Forming Multifunctional Ceramics with Different ZrO2 Polymorphs: Mixed Ion-Electron Conducting Properties of Zirconium Titanium Oxides
Authors: Walker Robert A. , Sinrud Joshua B. , McIntyre Melissa 
Published: February 2024

Infiltrating porous electrodes with solution phase precursors is a strategy employed to improve performance, catalytic activity and longevity in high temperature electrochemical devices. For example, traditional Ni yttria-stabilized zirconia (Ni-YSZ) cermet anodes used in solid oxide fuel cells (SOFCs) are susceptible to carbon accumulation and to sulfur poisoning. To counter the effects of degradation, anodes have been infiltrated with secondary materials containing Sn, Ba, Al and a host of other constituents, typically at levels of 1-5% (by mass). Processing and preparing infiltrated electrodes, however, can lead to formation of new material phases that affect surface chemistry and electrode microstructure in unexpected ways.
In this work, XRD and Raman spectroscopy are used to investigate the formation of functional zirconium titanate secondary phases in Ti/Zr oxides. Different zirconia polymorphs (either pure or stabilized with small amounts of yttria (YSZ)) mechanically mixed with TiO2 and heated above 1000 ˚C in stagnant air react to form several secondary phases. For sintering temperatures > 1100 ˚C, mixtures of TiO2 and m-ZrO2 form a ZrTiO4 secondary phase while mixtures of TiO2 and 3YSZ or 8YSZ form Zr5Ti7O24. The extent of secondary phase formation is enhanced with both higher sintering temperature and yttria content. The Zr5Ti7O24 secondary phase formed from TiO2/8YSZ samples sintered at 1400 ˚C exhibits unexpected mixed ionic and electronic conductivity at 800 ˚C. These findings suggest that secondary phases intentionally integrated into electrode architectures can improve the performance of high temperature electrocatalyst systems.
Solid Oxide Electrochemical Cells for Nitrogen and Oxygen Production
Authors: Sun Xiufu , Mondi Francesco , Monich Patricia Rabelo , Pirou Stéven , Frandsen Henrik Lund , Hendriksen Peter Vang 
Published: February 2024

Nitrogen and oxygen are both very important commodities with a wide variety of applications in industries, such as chemical, food and metallurgical plants as well as in the medical sector. Nowadays most of the nitrogen and oxygen are produced via air separation technologies such as cryogenic distillation (ASU) or pressure swing adsorption (PSA). Both ASU and PSA offer economical and mature ways for nitrogen and oxygen production at large (>100 ton/day) or medium scales (20-100 tons/day). If one can develop a technology for providing these gases in an energy efficient and cost effective way also at small scale, preferably driven by electricity only, this would enable new applications of the gases. Such a technology would match characteristics of the future green electricity system relying on small scale (few MWs) power generation and fluctuating production..
In this work we present an efficient electrochemical process for N2 and O2 production based on a solid oxide electrochemical cell technology by oxygen extraction from air. Cells with a 53 × 53 mm2 size were produced by a conventional tape casting method. They consist of a ca.10 μm CGO (Ce0.9Gd0.1O2-δ) electrolyte sandwiched between composite electrodes made from either LSCF (La0.6Sr0.4Co0.2Fe0.8O3-δ) - CGO, or LSF (La0.6Sr0.4FeO3-δ) - CGO. To boost performance at low temperature, the electrodes were infiltrated with Pr-oxide. The electrochemical performance with the different supports were characterized by obtaining current-voltage (iV) characteristics at different temperatures as well as through electrochemical impedance spectroscopy(EIS) with or without infiltration. For characterization, air was used as feed stock to the cathode compartment and air, or oxygen was used as sweep gas to the anode compartment. A voltage below 200 mV is needed to drive a current of 1 A/cm2 through the cell, which can provide a purity of 90% of N2 out at an operation temperature of 650 °C (see Figure 1a). The cells were demonstrated to operate for producing a 98% pure N2 stream without degradation over a 1500 h period (see Figure 1b).
Further analysis show that the specific power consumption calculated based on the power input and outlet gas flow rate for 90% N2 production is ca. 0.1 kWh/m3 and the specific power consumption for 96% and 98% N2 production is 0.21 and 0.31 kWh/m3, respectively. A 3-fold increase in required power is observed when going from a N2 purity from 90% to 98%.
Detailed electrochemical analysis and the electrochemical performance comparison between LSCF and LSF based mixed ionic electronic conductor (MIEC) electrodes will be presented. Factors limiting cell performance will as well as analysis of optimal point of operation in terms of energy consumption and reliability will also be discussed.

Acknowledgment

This project has received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement No 862482.

Figure 1
Managing the Scaling Relationship for Plasma-Activated Electrolysis Toward Nitrogen Fixation
Authors: Bera Susanta , Jung Myung-Jin , Kwon Se-Hun , Herrmann Anja , van de Sanden Richard , Tsampas Michail N. 
Published: February 2024

To substitute fossil feedstock, storing renewable electricity in chemical bonds has become one of the tremendous and attractive approaches. This approach enables the transformation of base molecules (i.e., H2O, N2, CO2) into energy or chemical-rich molecules. The energy stored in the nitrogen-based compound is a critical biogeochemical cycle in nature due to its essential nutrient for living organisms in the forms of ammonia, nitrates, urea, amino acids, and DNA/RNA nucleotides as well as the high atmospheric volume of 78%. Artificial nitrogen fixation via a catalytic approach powered by sustainable renewables (e.g. wind, solar) provides an alternative as well as promising route to resource the value-added chemicals.
N2 is a nonreactive base molecule due to its non-polarity and a strong triple bond between the atoms. Subsequently, even with an active catalyst, a substantial amount of energy is needed to activate N2 [1]. This Account covers our group’s recent advances in solid oxide electrolysis cells (SOECs) for providing reacting species on catalysts in a controllable manner while a radio frequency (RF) plasma is used to increase the reactivity of nitrogen [2,3]. Using oxygen ion or proton conducting SOECs we can produce either ammonia or nitric oxide (via reacting with plasma-activated N2) by suppressing oxygen or hydrogen evolution, respectively. The spatial separation of nitrogen dissociation and catalytic formation of the target molecules provides true independent parameters to optimize the electrocatalytic reactions. In both cases, the concentration of products is orders of magnitude higher than equilibrium (in the absence of plasma) while very high selectivity to nitrogen fixation is observed.
To date most of the studies have focused on the material axis, however, recent theoretical studies have revealed that large-scale N2 fixation necessitates the rational design of the reactor, catalyst selectivity, reaction kinetics, and fluid dynamics and thus it keeps the processes far from the optimum performance. In this contribution, we investigate several aspects including flow dynamics, nature of the catalyst, activation energy of the catalytic process, catalyst surface-to-volume ratio, catalyst selectivity, and residence time of plasma-activated nitrogen to reach the catalyst surface, toward solving the aforementioned limitations.

References

[1] H. Ma, R. K Sharma, S. Welzel, M. CM van de Sanden, M. N Tsampas, W. F. Schneider, Nat. Commun. 13 (2022) 402.
[2] R. K. Sharma, H. Patel, U. Mushtaq, V. Kyriakou, G. Zafeiropoulos, F. Peeters, S. Welzel, M. CM van de Sanden, M. N. Tsampas, ACS Energy Lett. 6 (2020) 313.
[3] H. Patel, R. K. Sharma, V. Kyriakou, A. Pandiyan, S. Welzel, M. C.M. van de Sanden, M. N. Tsampas, ACS Energy Lett. 4 (2019) 2091.

Figure 1
Preparation of Textured Polycrystalline La2NiO4+
δ
Membranes and Their Oxygen-Transporting Properties
Authors: Escobar Cano Giamper Eliseo , Zhao Zhijun , Riebesehl Fabian , Stölting Oliver , Breidenstein Bernd , Feldhoff Armin 
Published: February 2024

Due to its high chemical and thermal stability in CO2 atmosphere and its anisotropic crystal structure, the Ruddlesden-Popper phase La2NiO4+δ
has attracted considerable attention in the research field of oxygen-transporting membranes. The anisotropic properties of La2NiO4+δ
can be exploited in textured polycrystalline membranes to control the oxygen diffusion through this material. To fabricate textured La2NiO4+δ
membranes, powder mixtures consisting of fine-grained equiaxial La2NiO4+δ
matrix particles and large plate-like La2NiO4+δ
template particles in different mass ratios were uniaxially pressed and then sintered in air. For this purpose, the anisotropic template particles were synthesized by molten-flux method using NaOH as flux [1]. In the powder mixture, the La2NiO4+δ
template particles can be aligned perpendicular or parallel to the pressing direction, depending on the geometry of the pressing tool and the sample preparation. After the sintering process, textured La2NiO4+δ
membranes were obtained, which was verified by measuring X-ray diffraction patterns and pole figures. Further X-ray diffraction measurements together with the calculation of the Lotgering orientation factor revealed that an increasing content of the template particles in the ceramic materials leads to a stronger texturing. Scanning electron microscopy micrographs show some individual plate-like

La2NiO4+δ
grains well embedded in the matrix. Homogeneous distribution of lanthanum, nickel and oxygen in the ceramics was confirmed by energy-dispersive X-ray spectroscopy. Finally, the influence of the template particle content in the La2NiO4+δ
membranes on the oxygen permeation performance is discussed.
[1] Escobar Cano, G.; Brinkmann, Y.; Zhao, Z.; Kißling, P.A.; Feldhoff, A. Sol–Gel-Process-Based Molten-Flux Synthesis of Plate-like La2NiO4+

δ
Particles. Crystals
2022, 12, 1346. https://doi.org/10.3390/cryst12101346
Non-Arrhenius Ionic Conductivity Behaviour in Antiperovskite Solid Electrolytes for Sodium Metal Batteries
Authors: Darminto Brigita D , Pasta Mauro , Lee Hyeon Jeong , Guo Hua , Rees Gregory , Cattermull John , Diaz-Lopez Maria , Hashi Kenjiro , Kuwata Naoaki , Goodwin Andrew 
Published: February 2024

Solid-state sodium metal batteries have been proposed as an alternative to lithium-ion batteries (LIBs) for next-generation applications due to the high abundance and wide distribution of sodium resources.1 Sodium antiperovskites (Na3OX, X = Cl, Br, or BH4) have recently attracted great interest as solid electrolyte candidates due to the relatively low processing temperature (<500 oC), reasonable ionic conductivity (up to 4.4 x 10-3 S cm-1 at room temperature), and great chemical stability against sodium metal anodes.2,3 Typical solid-state ionic conductors have temperature-dependent ionic conductivity that follows Arrhenius behaviour over a broad range of temperatures, corresponding to a constant activation energy Ea. However, this is not the case in Na3OBr, and instead a phenomenon resulting in a higher ionic conductivity and lower activation energy is observed to occur at 255 oC. Similar non-Arrhenius ionic conductivity phenomenon has also been reported in the potassium antiperovskite K3OI. It has been proposed that this behaviour originated from anion disordering, but conclusive experimental evidence to support this claim has not been reported.4 An understanding of the origin of this behaviour could enable the synthesis route to be optimised such that higher ionic conductivities could be achieved.
In this work, we combined temperature-resolved bulk and local characterisation methods including Pawley and Rietveld refinements of synchrotron x-ray diffraction (XRD), pair distribution function (PDF), solid-state nuclear magnetic resonance (NMR) spectroscopy, and electrochemical impedance spectroscopy (EIS) to gain an insight into the origin of this non-Arrhenius behaviour. We found that this phenomenon does not originate from anion disordering, as previously speculated, because the lattice parameter of Na3OBr changed linearly with temperature and no major intensity changes were observed in the Na-Br and Na-O signals in the PDF patterns. Other supporting findings that lead us to this conclusion will be discussed in the presentation.
References

Wang, X. et al. Ultra-stable all-solid-state sodium metal batteries enabled by perfluoropolyether-based electrolytes. Nat. Mater.
21, 1057–1066 (2022).

Zheng, J., Perry, B. & Wu, Y. Antiperovskite Superionic Conductors: A Critical Review. ACS Mater. Au
1, 92–106 (2021).

Sun, Y. et al. Rotational Cluster Anion Enabling Superionic Conductivity in Sodium-Rich Antiperovskite Na3OBH4. J. Am. Chem. Soc.
141, 5640–5644 (2019).

Zheng, J. et al. Antiperovskite K3OI for K-Ion Solid State Electrolyte. J. Phys. Chem. Lett.
12, 7120–7126 (2021).