Hydration Entropy and Enthalpy of a Perovskite Oxide from Oxygen Tracer Diffusion Experiments

Kler, Joe; Souza, Roger A. De

doi:10.1021/acs.jpclett.2c00970

Cited by 4 publications

(22 citation statements)

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“…A detailed treatment within the framework of linear irreversible thermodynamics is given elsewhere; [59] its application has been demonstrated in a number of publications. [15,37,52,53] In line with previous studies [15,37,49,52,53,59] and consistent with results obtained here, we assume a positively charged surface core and a negative space-charge zone.…”

Section: Probing a Surface Space-charge Layer With A Tracer Diffusion...supporting

confidence: 92%

“…[15] Significantly lower space-charge potentials were found for the (110) and (111) surfaces, and these values are in good agreement with those reported for the (100) surface under wet conditions. [37] In these terms (of agreement with literature data [15,37] ), the behavior of Φ 0 in Figure 6 is remarkably similar to that of k O * in Figure 5. Unfortunately, the data quality in the former does not allow us to separate clearly the data into hightemperature and low-temperature regimes.…”

Section: Surface Space-charge Potentialsupporting

confidence: 88%

“…The green hexagons refer to data reported for “dry” exchange experiments for (100) oriented SrTiO 3 ; [ 15 ] the dark blue diamonds refer to data reported for “wet” exchange experiments for (100) oriented SrTiO 3 . [ 37 ]…”

Section: Resultsmentioning

confidence: 99%

“…The green hexagons refer to "dry " data for (100) oriented SrTiO 3 ; [15] the blue diamonds refer to "wet" data for (100) oriented SrTiO 3 . [37] T < T tr the same H 2 O-derived surface species that produce higher O * k also produce lower Φ 0 . Electrostatic charging of an interface and the attendant formation of space-charge zones arises in general terms from the segregation of charge carriers to the interface.…”

Section: Surface Space-charge Potentialmentioning

confidence: 95%

“…Temperature dependence of the surface space-charge potential Φ 0 for (100) (black squares), (110) (red circles), and (111) (light blue triangles) oriented SrTiO 3 surfaces. The error bars are smaller than the symbols.The green hexagons refer to data reported for "dry" exchange experiments for (100) oriented SrTiO 3 ;[15] the dark blue diamonds refer to data reported for "wet" exchange experiments for (100) oriented SrTiO 3 [37].…”

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confidence: 99%

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Surface Space‐Charge Potential and Oxygen Surface Exchange Coefficient of SrTiO₃: The Effect of Surface Orientation

Kler

Börgers

Souza

2022

Adv Materials Inter

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18O2/16O2 exchange experiments on terminated (100), (110), and (111) oriented samples of single‐crystal SrTiO3 are used to study the effect of surface orientation on the oxygen surface exchange coefficient kO∗\[k_{\rm{O}}^*\] and the surface space‐charge potential Φ0. Isotope exchanges are carried out at temperatures 922 < T/K < 1073 at an oxygen activity aO2 = 0.2 in dry conditions (aH2O < 10−7.7); isotope profiles are measured subsequently by secondary ion mass spectrometry. Isothermal kO∗$k_{\rm{O}}^*$ values are found to vary by less than one order of magnitude, with kO∗false(111false)≈kO∗false(110false)>kO∗false(100false)$k_{\rm{O}}^*(111) \approx k_{\rm{O}}^*(110){\bm{ > }}k_{\rm{O}}^*(100)$. All kO∗$k_{\rm{O}}^*$ data are consistent with a change in the activation enthalpy of surface exchange from 3.0 eV at high temperatures to 1.8 eV at lower temperatures. The transition is attributed to a change from a charge‐transfer mechanism at high temperatures to a mechanism involving surface OH species. The transition temperature depends on the surface orientation, Ttr(111) ≈ Ttr(110) > Ttr(100). Values of Φ0 obtained varied between 0.50 V and 0.37 V, with isothermal values obeying Φ0(111) ≈ Φ0(110) < Φ0(100). Φ0 data is analysed to obtain the OH− surface coverage for the low‐temperature regime. Similarities between the behavior of Φ0 and that of kO∗$k_{\rm{O}}^*$ are highlighted.

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Section: Probing a Surface Space-charge Layer With A Tracer Diffusion...supporting

confidence: 92%

Section: Surface Space-charge Potentialsupporting

confidence: 88%

Section: Resultsmentioning

confidence: 99%

Section: Surface Space-charge Potentialmentioning

confidence: 95%

mentioning

confidence: 99%

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Surface Space‐Charge Potential and Oxygen Surface Exchange Coefficient of SrTiO₃: The Effect of Surface Orientation

Kler

Börgers

Souza

2022

Adv Materials Inter

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Cation Exchange in Lead Halide Perovskite Quantum Dots toward Functional Optoelectronic Applications

Zhao,

Shi,

Huang

et al. 2023

Small Science

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Lead halide perovskite quantum dots (PQDs) exhibit properties tunability and solution processability, rending them highly promising for optoelectronic applications. To overcome the compositional limits of thin‐film perovskite and achieve mixed A‐site PQDs, a post‐synthetic cation‐exchange process, driven by the intrinsic ionic character as well as the dynamic surface structure within the PQDs, emerges as a highly efficient approach. The cation‐exchange process can be precisely regulated by manipulating PQD‐situated environment, such as the cation species, stoichiometric ratios, and surface ligand conditions, leading to tunable optical bandgap, improved stability, and enhanced carrier lifetime over the single A‐site PQDs. These advancements hold immense potential for elevating the performance of PQD‐based optoelectronic devices. In this perspective, a timely summary and outlook on the emergence and developments of cation exchange in functional PQDs is presented, as well as the intrinsic cation‐exchange mechanism and properties of these resultant‐mixed‐cation PQDs. It is believed that these detailed discussions are beneficial for advancing further development of cation exchange and utilization of mixed‐cation PQDs toward functional optoelectronic applications.

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Studying Surface Chemistry of Mixed Conducting Perovskite Oxide Electrodes with Synchrotron-Based Soft X-rays

Sha,

Kerherve,

van Spronsen

et al. 2023

J. Phys. Chem. C

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A fundamental understanding of the electrochemical reactions and surface chemistry at the solid−gas interface in situ and operando is critical for electrode materials applied in electrochemical and catalytic applications. Here, the surface reactions and surface composition of a model of mixed ionic and electronic conducting (MIEC) perovskite oxide, (La 0.8 Sr 0.2 ) 0.95 Cr 0.5 Fe 0.5 O 3-δ (LSCrF8255), were investigated in situ using synchrotron-based near-ambient pressure (AP) X-ray photoelectron spectroscopy (XPS) and nearedge X-ray absorption fine-structure spectroscopy (NEXAFS). The measurements were conducted with a surface temperature of 500 °C under 1 mbar of dry oxygen and water vapor, to reflect the implementation of the materials for oxygen reduction/evolution and H 2 O electrolysis in the applications such as solid oxide fuel cell (SOFC) and electrolyzers. Our direct experimental results demonstrate that, rather than the transition metal (TM) cations, the surface lattice oxygen is the significant redox active species under both dry oxygen and water vapor environments. It was proven that the electron holes formed in dry oxygen have a strong oxygen character. Meanwhile, a relatively higher concentration of surface oxygen vacancies was observed on the sample measured in water vapor. We further showed that in water vapor, the adsorption and dissociation of H 2 O onto the perovskite surface were through forming hydroxyl groups. In addition, the concentration of Sr surface species was found to increase over time in dry oxygen due to Sr surface segregation, with the presence of oxygen holes on the surface serving as an additional driving force. Comparatively, less Sr contents were observed on the sample in water vapor, which could be due to the volatility of Sr(OH) 2 . A secondary phase was also observed, which exhibited an enrichment in B-site cations, particularly in Fe and relatively in Cr, and a deficiency in A-site cation, notably in La and relatively in Sr. The findings and methodology of this study allow for the quantification of surface defect chemistry and surface composition evolution, providing crucial understanding and design guidelines in the electrocatalytic activity and durability of electrodes for efficient conversions of energy and fuels.

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Hydration Entropy and Enthalpy of a Perovskite Oxide from Oxygen Tracer Diffusion Experiments

Abstract: Water incorporation into perovskite oxides generates protonic defects in the form of hydroxide ions. In this study, an indirect method to probe the thermodynamics of water incorporation is demonstrated. Acceptor-doped single-crystal samples of SrTiO 3 were subjected to H 2 18

Cited by 4 publications

References 50 publications

Surface Space‐Charge Potential and Oxygen Surface Exchange Coefficient of SrTiO₃: The Effect of Surface Orientation

Surface Space‐Charge Potential and Oxygen Surface Exchange Coefficient of SrTiO₃: The Effect of Surface Orientation

Cation Exchange in Lead Halide Perovskite Quantum Dots toward Functional Optoelectronic Applications

Studying Surface Chemistry of Mixed Conducting Perovskite Oxide Electrodes with Synchrotron-Based Soft X-rays

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Hydration Entropy and Enthalpy of a Perovskite Oxide from Oxygen Tracer Diffusion Experiments

Abstract: Water incorporation into perovskite oxides generates protonic defects in the form of hydroxide ions. In this study, an indirect method to probe the thermodynamics of water incorporation is demonstrated. Acceptor-doped single-crystal samples of SrTiO 3 were subjected to H 2 18

Cited by 4 publications

References 50 publications

Surface Space‐Charge Potential and Oxygen Surface Exchange Coefficient of SrTiO3: The Effect of Surface Orientation

Surface Space‐Charge Potential and Oxygen Surface Exchange Coefficient of SrTiO3: The Effect of Surface Orientation

Cation Exchange in Lead Halide Perovskite Quantum Dots toward Functional Optoelectronic Applications

Studying Surface Chemistry of Mixed Conducting Perovskite Oxide Electrodes with Synchrotron-Based Soft X-rays

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Product

Resources

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Surface Space‐Charge Potential and Oxygen Surface Exchange Coefficient of SrTiO₃: The Effect of Surface Orientation

Surface Space‐Charge Potential and Oxygen Surface Exchange Coefficient of SrTiO₃: The Effect of Surface Orientation