Oxygen Exchange Kinetics Research Articles

Thermal stability and coalescence dynamics of exsolved metal nanoparticles at charged perovskite surfaces

Exsolution reactions enable the synthesis of oxide-supported metal nanoparticles, which are desirable as catalysts in green energy conversion technologies. It is crucial to precisely tailor the nanoparticle characteristics to optimize the catalysts’ functionality, and to maintain the catalytic performance under operation conditions. We use chemical (co)-doping to modify the defect chemistry of exsolution-active perovskite oxides and examine its influence on the mass transfer kinetics of Ni dopants towards the oxide surface and on the subsequent coalescence behavior of the exsolved nanoparticles during a continuous thermal reduction treatment. Nanoparticles that exsolve at the surface of the acceptor-type fast-oxygen-ion-conductor SrTi0.95Ni0.05O3−δ (STNi) show a high surface mobility leading to a very low thermal stability compared to nanoparticles that exsolve at the surface of donor-type SrTi0.9Nb0.05Ni0.05O3−δ (STNNi). Our analysis indicates that the low thermal stability of exsolved nanoparticles at the acceptor-doped perovskite surface is linked to a high oxygen vacancy concentration at the nanoparticle-oxide interface. For catalysts that require fast oxygen exchange kinetics, exsolution synthesis routes in dry hydrogen conditions may hence lead to accelerated degradation, while humid reaction conditions may mitigate this failure mechanism.

Application of novel Dy0.06Gd0.02Er0.02Bi1.9O3 oxide ion electrolyte for intermediate-temperature reversible solid oxide cells

Bismuth-based oxides are promising electrolyte materials for Reversible Solid Oxide Cells (RSOCs) due to their high ion conductivity and rapid surface oxygen exchange kinetics. In this work we propose a multi-element doping strategy to obtain a novel Dy0.06Gd0.02Er0.02Bi1.9O3 (DGESB) quaternary oxide bismuth material whose ionic conductivities and crystal structure are characterized by AC impedance and X-ray diffraction technique in the temperature range from 600 to 700 °C. Along with promising structure stability and durability, our novel DGESB showed a remarkable ionic conductivity that is 65 times higher than the commercial yttria-stabilized zirconia (YSZ) electrolyte at 700 °C. With composite electrode of DGESB + LCN (LaCo0.6Ni0.4O3) and DGESB/YSZ bilayer electrolyte consisting of RSOC symmetric cell, which achieves a high peak power density (PPD) of 1.62 W/cm2 in fuel cell mode which is 2.7 times higher than that of YSZ single-layer electrolyte, while the electrolysis current density is as high as 1.66 A/cm2 at 1.3 V under H2/H2O:50/50 in electrolysis mode at the same operation temperature of 700 °C. The electrochemical performance measurements revealed a certain stable operation for 200 h in fuel cell mode. The performance degradation can be attributed to the microstructure evolution at the interface between electrolyte and electrodes. The high ionic conductive DGESB proves to be an excellent intermediate electrolyte layer for improving cell performance in RSOCs

16O2 – 18O2 interface exchange study between gas phase and the BaFeO3–δ oxide

Studies of oxygen surface exchange kinetics for BaFeO3–δ oxide were performed using the oxygen isotope exchange method with pulsed supply of an isotopically enriched mixture (PIE) at the partial oxygen pressure 21.3 kPa in the temperature range of 350–600 °С. Oxygen surface exchange kinetics was considered in the framework of two-step model including two consecutive steps: dissociative adsorption of oxygen and incorporation of oxygen adatoms into the crystal lattice of the oxide. The rates of oxygen heterogeneous exchange (rH), as well as the rates of dissociative adsorption (ra) and oxygen incorporation (ri), have been calculated. The process of oxygen dissociative adsorption at the surface of BaFeO3–δ oxide was found to be the rate-determining step of the surface exchange. The appropriate models describing the oxygen exchange kinetics and possible mechanisms occurring in the system “gaseous oxygen – BaFeO3–δ oxide” were discussed.

Effect of doping with iron and cations deficiency in the high conductive electrolyte La0.8Sr0.2Ga0.8Mg0.2O3–δ on oxygen exchange kinetics

The oxygen isotope exchange method was used to investigate the kinetics of the interaction between gaseous oxygen and LaGaO3-based oxides in a temperature range of 650 to 850 °C, with an oxygen pressure of 10 mbar. The stable isotopes of 18O/16O were used as labelled ions. The temperature dependencies of the heterogeneous oxygen exchange rate (rH), the oxygen dissociative adsorption rate (ra), the oxygen incorporation rate (ri), and the oxygen diffusion coefficient (D) were determined. A comparative analysis of the rH and D values for La0.8Sr0.2Ga0.8Mg0.2O3–δ was carried out with a view to identifying any similarities or differences when compared with the literature data on oxides with similar compositions. The effect of FeGa′ doping and the creation of an A-sublattice deficiency on the kinetic characteristics were investigated using the (La0.8Sr0.2)0.98Ga0.7Fe0.1Mg0.2O3–δ oxide as a case example. Correlations between the rate-determining step of oxygen exchange and the modification of the oxide composition were identified.

Interface engineering of La0.6Sr0.4Co0.2Fe0.8O3−δ/Gd0.1Ce0.9O1.95 heterostructure oxygen electrode for solid oxide electrolysis cells with enhanced CO2 electrolysis performance

For CO2 electrolysis in solid oxide electrolysis cells (SOECs), oxygen evolution reaction in the oxygen electrode limits the electrolysis process due to its slower reaction kinetics. Composite oxygen electrodes with good uniformity and interfacial connectivity are expected to promote the charge carriers' transport effectively and thus increase the electrocatalytic performance of the cell. In this work, interface engineering is applied to promote the conventional La0.6Sr0.4Co0.2Fe0.8O3−δ-Gd0.1Ce0.9O1.95 (LSCF-GDC) composite oxygen electrode to form a heterostructure via co-synthesis method. The results prove that LSCF co-synthesized with 40 wt%GDC (LSCF/40GDC) exhibits higher conductivity and faster oxygen exchange kinetics and bulk diffusion processes. The nickel/yttria stabilized zirconia (Ni-YSZ) supported cell with LSCF/40GDC oxygen electrode could approach an impressive CO2 electrolysis current density of 2.6 A·cm−2 at 1.6 V and 800 °C. Meanwhile the cell can operate at 1.5 V and 750 °C with electrolysis current density of 1.3 A·cm−2 for more than 100 h without apparent degradation. This heterostructure enhances the interfacial bonding strength between LSCF and GDC phases, thereby providing a continuous network structure for electron and ion transport. Such an interface engineering via co-synthesis method offers a straightforward and convenient modification for oxygen electrodes, providing an alternative route for advanced materials development of CO2 electrolysis.

An efficient electrode for reversible oxygen reduction/evolution and ethylene electro-production on protonic ceramic electrochemical cells

Protonic ceramic electrochemical cells (PCECs) have demonstrated great promise for applications in the generation of electricity, and the synthesis of chemicals (for example, ethylene). However, enhancing the electrochemical reactions kinetics and stability of PCECs electrodes is one grand challenge. Here, we present a novel electrode material via a co-doping of cesium (Cs) and niobium (Nb) on PrBaCo2O6−δ with the composition of PrBa0.9Cs0.1Co1.9Nb0.1O6−δ (PBCCN), which naturally decomposes into dual phases of a double-perovskite PBCCN (DP-PBCCN, ∼92.3 wt%) and a single-perovskite Ba0.9Cs0.1Co0.95Nb0.05O3−δ (SP-BCCN, ∼7.7 wt%) under typical powder processing conditions. PBCCN exhibits a low area-specific resistance (ASR) value of 0.107 Ω cm2, an outstanding performance of 2.04 W cm−2 in fuel cell (FC) mode, a current density of −2.84 A cm−2 at 1.3 V in electrolysis cell (EC) mode, and promising reversible operational durability of 53 cycles in ∼212 h at +/− 0.5 A cm−2 and 650 °C. Cs doping generates more oxygen vacancies and accelerates the oxygen exchange kinetics, while Nb doping effectively enhances the stability, as illustrated by the analyses of X-ray photoelectron spectroscopy, and electrical conductivity relaxations. When applied as the positrode for electrochemical non-oxidative dehydrogenation of ethane (C2H6) to ethylene (C2H4) on PCECs, it displays an encouraging C2H6 conversion of 12.75% and a C2H4 selectivity of 98.4% at 1.2 V.

Kinetics of oxygen exchange with oxides Ba0.5Sr0.5(Co0.8Fe0.2)1−xMexO3−ẟ (Me = Ta, W) in non-equilibrium conditions

Kinetics of oxygen exchange with oxides Ba0.5Sr0.5(Co0.8Fe0.2)1−xMexO3−ẟ (Me = Ta, W) in non-equilibrium conditions

Enhancing the CO2 Adsorption of the Cobalt-Free Layered Perovskite Cathode for Solid-Oxide Electrolysis Cells Gains Excellent Stability under High Voltages via Oxygen-Defect Adjustment.

Solid-oxide electrolysis cells are a clean energy conversion device with the ability to directly electrolyze the conversion of CO2 to CO efficiently. However, their practical applications are limited due to insufficient CO2 adsorption performance of the cathode materials. To overcome this issue, the A-site cation deficiency strategy has been applied in a layered perovskite PrBaFe1.6Ni0.4O6-δ (PBFN) cathode for direct CO2 electrolysis. The introduction of 5% deficiency at the Pr/Ba site leads to a significant increase in the concentration of oxygen vacancies (nonstoichiometric number δ of oxygen vacancies increased from 0.093 to 0.132), which greatly accelerates the CO2 adsorption performance as well as the O2- transport capacity toward the CO2 reduction reaction (CO2RR). CO2 temperature-programmed desorption indicates that A-site cation-deficient (PrBa)0.95Fe1.6Ni0.4O6-δ (PB95FN) shows a larger desorption peak area and a higher desorption temperature. PB95FN also exhibits a greater presence of carbonate in Fourier transform infrared (FT-IR) spectroscopy. The electrical conductivity relaxation test shows that the introduction of the 5% A-site deficiency effectively improves the surface oxygen exchange and diffusion kinetics of PB95FN. The current density of the electrolysis cell with the (PrBa)0.95Fe1.6Ni0.4O6-δ (PB95FN) cathode reaches 0.876 A·cm-2 under 1.5 V at 800 °C, which is 41% higher than that of PB100FN. Moreover, the PB95FN cathode demonstrates excellent long-term stability over 100 h and better short-term stability than PB100FN under high voltages, which can be ascribed to the enhanced CO2 adsorption performance. The PB95FN cathode maintains a porous structure and tightly binds to the electrolyte after stability testing. This study highlights the potential of regulating oxygen defects in layered perovskite PrBaFe1.6Ni0.4O6-δ cathode materials via incorporation of cation deficiency toward high-temperature CO2 electrolysis.

Oxygen exchange kinetics of mixed conducting oxide ceramics covered by dendritic surface particles

The oxygen exchange process between the gas phase and a mixed conducting solid oxide was simulated by application of finite element modeling (FEM). The solid oxide was covered by inert surface particles of different shape and size. The effect of spherical, ellipsoidal, rectangular, and dendritic surface particles on the oxygen exchange kinetics was elaborated in detail. Relaxation curves for the total amount of exchanged oxygen upon an instantaneous change of the oxygen activity (partial pressure) of the surrounding atmosphere were calculated. One-dimensional analytical solutions of the diffusion equations were fitted to the numerically calculated relaxation curves, yielding apparent chemical diffusivities and surface exchange coefficients. The FEM simulations of the oxygen exchange process were carried out as a function of surface coverage for the various particle types. The apparent surface exchange coefficient decreased with increasing surface coverage. In case of small spherical and ellipsoidal particles with a fairly small extension of the shorter axis (large aspect ratio) the surface exchange coefficient decreased almost linearly with increasing surface coverage caused by the reduction of the active (uncovered) surface area. An additional decrease of the surface exchange coefficient (non-linear variation with surface coverage) was observed with respect to dendritic particles. This peculiar behavior could be interpreted in terms of flux constriction effects, i.e. lateral diffusion processes underneath the inert surface particles. The surface area blocked for the exchange reaction seems to be significantly larger than the cross-section of the dendritic surface particles.

Cross-Validation of the Remarkably High Surface Oxygen Exchange Kinetics of PrBa0.5Sr0.5Co1.5Fe0.5O5+δ: A Combined Thin-Film Mass Relaxation and Bulk Electrical Conductivity Relaxation Study.

In this work, we measure the oxygen kinetic properties of double perovskite PrBa0.5Sr0.5Co1.5Fe0.5O5+δ (PBSCF), a material widely used as the air electrode in solid oxide electrochemical cells, by mass relaxation (MR) and electrical conductivity relaxation (ECR) experiments. MR studies are carried out using thin films deposited on a gallium phosphate piezocrystal microbalance, and ECR studies are performed using a bulk bar sample with 97% theoretical density. Measurements are performed at 600 °C over the temperature oxygen partial pressure range from 10-4 to 0.21 atm. Despite the differences in experimental formats and surface microstructural features, the ks values extracted from the two methods are found to be in good agreement with one another. The rate constant is found to increase with oxygen partial pressure with a power law dependence, rising from 1.0 × 10-6 cm/s at 3.2 × 10-4 atm to 1.2 × 10-4 cm/s at 0.24 atm, as averaged over the oxidation and reduction directions. The rates in the oxidation direction are observed to be slightly higher than those in the reduction direction for a given pair of pO2 values, suggesting that the final pO2 value controls the overall relaxation behavior. The power law exponent describing the dependence of ks on pO2 is found to be 0.74 ± 0.01. The ECR study of the bulk sample reveals that even with a diffusion length of 1.8 mm, the relaxation process is largely free of diffusion limitations, indicating that PBSCF has the high bulk transport properties required for a double-phase boundary oxidation/reduction pathway.

Alkali metal and alkali earth metal-modified La-Fe-based perovskite catalyzed coke combustion

Coke catalytic gasification is an efficient method of burning coke. The core of this technology is the preparation of efficient and stable catalysts. A series of different type La-Fe-based perovskite catalysts, including ABO3 (La1-xSrxFeO3, LaK0.04Sr0.25FeO3), R-P (LaK1.7Sr0.2Fe1.7O6) and A2B2O6 (LaKSr0.17Fe1.5O6, LaKSr0.2Fe1.8O6) were prepared by sol-gel method and calcination of metal-organic framework (MOF) precursor method. The activity of perovskite catalytic coke was tested by thermogravimetric analysis and tubular reactor. Among them, LaKSr0.17Fe1.5O6−MOF has the best catalytic activity, with T10, T50, and T90 values of 610.65 °C, 666.86 °C, and 705.84 °C, respectively. LaKSr0.17Fe1.5O6−MOF not only improves coke conversion but also reduces reaction temperature. DFT and experimental results show that doped K and Sr metals promote the formation of many active sites (oxygen vacancies) on the surface of LaKSr0.17Fe1.5O6−MOF, which reduces the adsorption energy of O2 molecules, realizes the oxygen exchange kinetics. The oxygen release regeneration process is achieved between perovskite lattice oxygen and O2 molecules. These processes synergistically promote coke conversion. In addition, it also has strong stable regeneration performance. These results provide a promising strategy for designing and preparing efficient and low-cost catalysts for the practical application of coke removal.

Spontaneous Growth of Perovskite‐Derived Oxide over Double Perovskite Surface for Enhancing Cathodic Performance in Protonic Ceramic Fuel Cells

AbstractRobust catalytic materials with high activity and stability play important roles in energy conversion and storage devices such as protonic ceramic fuel cells (PCFCs), in which a favourable cathode should possess high oxygen ion, proton and electron triple conductivities, and superior surface oxygen exchange kinetics. Herein, a thermal‐driven self‐construction phenomenon in cation‐nonstoichiometric Ba1+xGd1‐xCo2O6‐δ is reported, accordingly developing a new type of nanocomposite, that is, double perovskite BaGdCo2O6‐δ (DP‐BGCO) anchored by perovskite‐derived BaCoO3‐δ (P‐D‐BCO) nanoparticles, which, used as the cathode of PCFCs, demonstrates low area‐specific resistances of 0.053 and 0.026 ohm cm−2 respectively at 650 and 700 °C over BaZr0.3Ce0.5Y0.1Yb0.1O3‐δ protonic electrolyte and attractive peak power densities of 0.87 (650 °C) and 1.15 W cm−2 (700 °C) with outstanding stability, much superior to the similar cell with single‐phase BCO or BGCO cathodes. The synergy between the two components brings the outstanding performance with the mixed oxygen ion and electronic conducting perovskite‐derived oxide showing superior catalytic activity for oxygen reduction reaction while the double perovskite provides good bulk protonic conductivity to enlarge reaction sites. Such selective self‐construction, well manipulated through the A‐site cation stoichiometry engineering, provides a facile way for developing new high‐performance electrocatalysts with broad application potential.

Engineering surface dipoles on mixed conducting oxides with ultra-thin oxide decoration layers

Improving materials for energy conversion and storage devices is deeply connected with an optimization of their surfaces and surface modification is a promising strategy on the way to enhance modern energy technologies. This study shows that surface modification with ultra-thin oxide layers allows for a systematic tailoring of the surface dipole and the work function of mixed ionic and electronic conducting oxides, and it introduces the ionic potential of surface cations as a readily accessible descriptor for these effects. The combination of X-ray photoelectron spectroscopy (XPS) and density functional theory (DFT) illustrates that basic oxides with a lower ionic potential than the host material induce a positive surface charge and reduce the work function of the host material and vice versa. As a proof of concept that this strategy is widely applicable to tailor surface properties, we examined the effect of ultra-thin decoration layers on the oxygen exchange kinetics of pristine mixed conducting oxide thin films in very clean conditions by means of in-situ impedance spectroscopy during pulsed laser deposition (i-PLD). The study shows that basic decorations with a reduced surface work function lead to a substantial acceleration of the oxygen exchange on the surfaces of diverse materials.

Toward solid-state Limetal-air batteries; an SOFC perspective of solid 3D architectures, heterogeneous interfaces, and oxygen exchange kinetics.

The full electrification of transportation will require batteries with both 3-5× higher energy densities and a lower cost than what is available in the market today. Energy densities of >1000 W h kg-1 will enable electrification of air transport and are among the very few technologies capable of achieving this energy density. Limetal-O2 or Limetal-air are theoretically able to achieve this energy density and are also capable of reducing the cost of batteries by replacing expensive supply chain constrained cathode materials with "free" air. However, the utilization of liquid electrolytes in the Limetal-O2/Limetal-air battery has presented many obstacles to the optimum performance of this battery including oxidation of the liquid electrolyte and the Limetal anode. In this paper a path towards the development of a Limetal-air battery using a cubic garnet Li7La3Zr2O12 (LLZ) solid-state ceramic electrolyte in a 3D architecture is described including initial cycling results of a Limetal-O2 battery using a recently developed mixed ionic and electronic (MIEC) LLZ in that 3D architecture. This 3D architecture with porous MIEC structures for the O2/air cathode is essentially the same as a solid oxide fuel cell (SOFC) indicating the importance of leveraging SOFC technology in the development of solid-state Limetal-O2/air batteries.

Enhanced oxygen exchange kinetics and long-term stability of Ruddlesden-Popper phase Pr4Ni3O10+δ cathode for solid oxide fuel cells

This research explores the intricacies of oxygen exchange kinetics in Pr4Ni3O10+δ (PNO), aiming to assess its potential as a viable cathode material for solid oxide fuel cell applications. Utilizing a...

Oxygen surface exchange kinetics of La1−xSrxCoO3–δ thin-films decorated with binary oxides: links between acidity, strontium doping, and reaction kinetics

Recent study shows the enhancement of oxygen exchange kinetics of oxygen electrodes using oxides selected using Smith acidity. However, what are the limits to this approach?

Sr-deficient medium-entropy Sr1-xCo0.5Fe0.2Ti0.1Ta0.1Nb0.1O3-δ cathodes with high Cr tolerance for solid oxide fuel cells

In this work, Sr-deficiency is proposed as an effective strategy to improve the oxygen reduction reaction (ORR) activity and Cr tolerance of medium-entropy Sr1-xCo0.5Fe0.2Ti0.1Ta0.1Nb0.1O3-δ (S1-xCFTTN, x=0–0.15) cathodes for intermediate temperature solid oxide fuel cells (IT-SOFCs). With proper Sr-deficiency, S0.95CFTTN possesses the highest electrical conductivity and fastest oxygen exchange kinetics within tested samples. The optimized cathode yields outstanding ORR activity with a polarization resistance of 0.024 Ω cm2 at 700 °C, much lower than 0.037 Ω cm2 for SCFTTN cathode. Based on these, an anode-supported cell with S0.95CFTTN cathode exhibits a peak power density of 1153.5 mW cm−2 at 800 °C, much higher than that with SCFTTN cathode. Moreover, the S0.95CFTTN cathode displays dramatically enhanced Cr tolerance ability, which is due to the Sr-deficient diminishes surface Sr segregation and subsequent the formation of SrCrO4. Our results indicate appropriate Sr-deficiency is an effective approach to enhance the ORR activity and stability of SOFC cathodes.

Enhancing oxygen exchange kinetics of solid oxide fuel cell cathode: Unleashing the potential of higher order Ruddlesden-Popper phase surface modification

Tailoring the electrode surface represents a promising strategy to enhance electrochemical performance while preserving base material integrity. Achieving appropriate surface coverage with catalytic active oxide material is critical for efficient oxygen transport at the triple phase boundary (TPB). To further explore this approach, the perovskite structure La0.6Sr0.4Co0.2Fe0.8O3-δ (LSCF) is decorated with a higher order Ruddlesden-Popper phase Pr4Ni3O10+δ (PNO). This combination is being investigated using electrical conductivity relaxation (ECR) technique to study the oxygen exchange kinetics. Samples with varying surface coverage of PNO are examined in a temperature range of 650 °C–850 °C, with a step change in pO2 between 0.1 atm and 0.21 atm. The chemical diffusion coefficient, Dchem, remains invariant across all the samples, however, the surface exchange coefficient, kchem, varies with the surface coverage of PNO. Notably, the coated sample with a PNO loading content of 0.28 mg cm−2, referred to as PNO5, demonstrates a significant enhancement of nearly two orders of magnitude in kchem compared to bare LSCF at 650 °C. This substantial improvement is ascribed to the increased active sites of ORR within the TPB region and the facilitated electron access through tunneling from LSCF to the coated phase. Pulse isotopic exchange (PIE) measurements on the fractionated powders confirm the fast surface exchange kinetics of PNO. Such remarkable oxygen exchange characteristics encourage the use of PNO, along with LSCF, as potential candidates for SOFC cathodes.

Recovery and Delay of Impurity-Induced Poisoning of Oxygen Exchange Kinetics in Mixed Conducting Oxides Via Controlled Surface Acidity

The oxygen exchange kinetics in mixed conducting oxide surfaces are critical to a variety of energy-related technologies, including solid oxide fuel/electrolyser cells (SOFCs/SOECs), permeation membranes, batteries, and sensors. Such devices, however, commonly suffer from performance degradation from impurity-poisoning during long-term operation, for example, chromia poisoning in SOFCs from metal interconnects or silica from furnace refractories. The acidity/basicity of binary additives has recently been found to be a sensitive descriptor for determining the oxygen exchange coefficient (kchem ) of mixed ionic/electronic conducting oxides (MIEC), systematically varing by over 6 orders of magnitude via controlled surface infiltration with binary oxides. These huge variations in kchem are attributed to changes in surface electron concentration induced by the additives.Inspired by these ideas, in this work we first demonstrate the ability to recover the oxygen exchange kinetics of MIEC oxides (e.g. Pr0.1Ce0.9O2-δ (PCO) and Sr(Ti,Fe)O3 (STF)) by counteracting acidic infiltrant’s impact on degradation, e.g. by chromia or silica, by compensating with a basic infiltrant like lithia or calcia. Further, we further demonstrate the ability to enhance impurity tolerance of MIEC oxides by pre-coating basic additives onto the electrodes. Such pre-treatments not only markedly improve the initial kchem of the pristine MIEC oxides, but markedly lower the rate of degradation induced by subsequent coatings with acidic poisons. Electrical conductivity relaxation measurements on porous MIEC specimens were used to examine the impact of infiltrants on kchem . In parallel, the area-specific resistance of screen-printed symmetric cells (cathode|electrolyte|cathode) were examined by electrochemical impedance spectroscopy.

Exploring Stable and Selective Anode Materials for the Electrochemical Oxidative Coupling of Methane (EOCM): A Case Study of Doped Titanates

The development of next-generation solid oxide fuel cells (SOFCs) relies on integrating materials such as La0.6Sr0.4Co0.2Fe0.8O3- δ (LSCF), which has been lauded for its fast oxygen ion and electron conduction, along with its high oxygen reduction activity.[1] However, the use of LSCF has been plagued by 1) stability issues caused by surface Sr precipitation and 2) subsequent poisoning by Cr- or S- containing species.We have previously shown that the introduction of more oxidizable cations at the electrode surface can effectively improve both the stability and the oxygen exchange kinetics of the electrodes. However, the influence of these cations, as with many dopant infiltration studies, is currently not fully understood across all possible modes of electrode surface stabilization/activity enhancement. For example, we have recently discovered that at 800°C and under air atmospheres (i.e. at typical SOFC operational conditions), these Hf/Zr surface cation dopants are mobile and diffuse into the lattice of a porous LSCF electrode as evidenced by their vanishing x-ray photoelectron signals. This is accompanied nevertheless by a noticeable electrode stabilization, suggesting a sub-surface effect of the introduced dopants.Inspired by this, in this work our aim is to uncover the mechanism responsible for the stabilization of the surface oxygen exchange kinetics. Our approach involves dense thin film LSCF as model system to investigate the temperature-dependent physicochemical properties of these surface and sub-surface dopant cations. We fabricate LSCF thin films via pulsed laser deposition onto single crystalline substrates and then introduce our targeted cations at the surface via an aqueous solution infiltration. We characterize the electrochemical performance of the thin films by performing chronoamperometric and impedance spectroscopic measurements to discern the extent of the temporal electrode performance degradation using metrics such as area-specific resistance. In parallel, we aim to rationalize the observed electrochemical performance stabilization using complementary surface science techniques. We propose investigating the cation dissolution phenomenon through a combination of x-ray photoelectron and Auger electron spectroscopies, along with atomic force microscopy, scanning/transmission electron microscopy, scanning tunnelling microscopy and grazing incidence thin film x-ray diffraction. This study aims to reveal the influence of sub-surface more oxidizable cations on the extent of Sr segregation and highlights how two major factors contribute to the observed trends: Electrode fabrication conditions, for example the dopant concentration dependence (insufficient or excessive surface dopant concentrations has previously been shown to suppress the stabilization effect).[3]Electrode operation conditions, for example the temperature profile experienced by the cell (higher temperatures lead to dopant dissolution). [1] SP Jiang, Int. J. Hydrogen Energy 44 (14), 7448 (2019).[2] N Tsvetkov et al., Nature Mat. 15 (9), 1010 (2016).[3] N Tsvetkov et al., Faraday Disc. 182 (0), 257 (2015).