Kinetics of Oxygen Surface Exchange on Epitaxial Ruddlesden–Popper Phases and Correlations to First-Principles Descriptors

Lee, Yueh‐Lin; Lee, Dongkyu; Wang, Xiao Renshaw; Lee, Ho Nyung; Morgan, Dane; Shao‐Horn, Yang

doi:10.1021/acs.jpclett.5b02423

Cited by 57 publications

(74 citation statements)

References 43 publications

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“…49 ), Sr 2− x La x MO 4± δ (ref. 50 ), and Ba 0.5 Sr 0.5 Co 0.75 Fe 0.25 O 3± δ (BSCF) 51 . Merkle calculated the band diagram for BSCF and found a similar electronic configuration as in LSNF, and Schmidt and co-workers saw that the catalytic activity of Ba 0.5 Sr 0.5 Co 0.8 Fe 0.2 O 3± δ was much higher than that of Ba 0.5 Sr 0.5 CoO 3± δ (ref.…”

Section: Discussionmentioning

confidence: 99%

“…PXRD patterns for the Rietveld refinement were taken with a Huber G670 Guinier diffractometer (Cu K α1 radiation; curved Ge(111) monochromator; image plate). The refinement was performed with the JANA2006 package 50 . As the electron diffraction patterns of all compositions revealed no deviation from the RP n = 1 I 4/ mmm structure, the La 2 NiO 4 structure 51 was used as a starting model.…”

Section: Methodsmentioning

confidence: 99%

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Exceptional electrocatalytic oxygen evolution via tunable charge transfer interactions in La0.5Sr1.5Ni1−xFexO4±δ Ruddlesden-Popper oxides

Forslund¹,

Hardin²,

Xi³

et al. 2018

Nat Commun

197

130

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The electrolysis of water is of global importance to store renewable energy and the methodical design of next-generation oxygen evolution catalysts requires a greater understanding of the structural and electronic contributions that give rise to increased activities. Herein, we report a series of Ruddlesden–Popper La0.5Sr1.5Ni1−xFexO4±δ oxides that promote charge transfer via cross-gap hybridization to enhance electrocatalytic water splitting. Using selective substitution of lanthanum with strontium and nickel with iron to tune the extent to which transition metal and oxygen valence bands hybridize, we demonstrate remarkable catalytic activity of 10 mA cm−2 at a 360 mV overpotential and mass activity of 1930 mA mg−1ox at 1.63 V via a mechanism that utilizes lattice oxygen. This work demonstrates that Ruddlesden–Popper materials can be utilized as active catalysts for oxygen evolution through rational design of structural and electronic configurations that are unattainable in many other crystalline metal oxide phases.

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Section: Discussionmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Exceptional electrocatalytic oxygen evolution via tunable charge transfer interactions in La0.5Sr1.5Ni1−xFexO4±δ Ruddlesden-Popper oxides

Forslund¹,

Hardin²,

Xi³

et al. 2018

Nat Commun

197

130

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“…To accomplish this, we used the O 2p-band center (see Section 2 of the SI for details) as an electronic structure descriptor, as this variable has proved useful for correlating with a number of perovskite properties. [6,[44][45][46] The B-site cation 3d-band center and the La/Sr A-site band centers (both calculated with respect to E Fermi ) were also investigated as possible descriptors.…”

Section: P-band Center As An Electronic Structure Descriptormentioning

confidence: 99%

Understanding and Controlling the Work Function of Perovskite Oxides Using Density Functional Theory

Jacobs

Booske

Morgan

2016

Adv Funct Materials

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153

116

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Perovskite oxides containing transition metals are promising materials in a wide range of electronic and electrochemical applications. However, neither their work function values nor an understanding of their work function physics have been established. Here, we predict the work function trends of a series of perovskite (ABO 3 formula) materials using Density Functional Theory, and show that the work functions of (001)-terminated AO-and BO 2 -oriented surfaces can be described using concepts of electronic band filling, bond hybridization, and surface dipoles. The calculated range of AO (BO 2 ) work functions are 1.60-3.57 eV (2.99-6.87 eV). We find an approximately linear correlation (R 2 between 0.77-0.86, depending on surface termination) between work function and position of the oxygen 2p band center, which correlation enables both understanding and rapid prediction of work function trends. Furthermore, we identify SrVO 3 as a stable, low work function, highly conductive material. Undoped (Ba-doped) SrVO 3 has an intrinsically low AO-terminated work function of 1.86 eV (1.07 eV). These properties make SrVO 3 a promising candidate material for a new electron emission cathode for application in high power microwave devices, and as a potential electron emissive material for thermionic energy conversion technologies.2

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“…3), Lee et al 7,37 of these two-phase films are given. In TEM, SEM and AFM images, 5 "spots" with a size of several nanometers can tentatively be observed for P films partially covered with R, resulting in potentially very high TPB densities.…”

Section: Activity Of Satp Films and Films Containing Metastable Phases-mentioning

confidence: 99%

Oxygen Exchange Activity of La-Sr-Co-O PLD Films and Quantification of (La,Sr)CoO_3-_δ/(La,Sr)₂CoO₄₊_δ/O₂Triple Phase Boundary Activity

Stämmler

Merkle

Maier

2017

J. Electrochem. Soc.

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Thin compact La-Sr-Co-O composite films consisting of (La,Sr)CoO 3-δ and (La,Sr) 2 CoO 4+δ crystallites were prepared by compositional phase separation during pulsed laser deposition. While the total La:Sr ratio is kept constant at 70:30, different phase ratios and crystallite sizes are investigated. The effect of hetero-interfaces on the oxygen reduction reaction (ORR) kinetics was investigated by impedance spectroscopy. The enhancement relative to the appropriate reference activity is quantified in terms of the triple phase boundary (TPB) length specific activity k TPB , resulting in k TPB = 2-9 · 10 −13 cm 2 /s at 600 • C. A metastable Co-deficient perovskite phase La 0.7 Sr 0.3 Co 0.9 O 3-δ formed in La-Sr-Co-O films under certain conditions was found to be highly active with an effective rate constant k q = 3 · 10 −6 cm/s at 600 • C, representing one possible source for the activity enhancement in these composite films. (La,Sr)CoO 3-δ /(La,Sr) 2 CoO 4±δ (perovskite phase, P/RuddlesdenPopper phase, R) two-phase materials were reported in literature to show enhanced activity for the oxygen reduction reaction (ORR) compared to reference single-phase samples 1-11 making them a promising new material for highly active cathodes in intermediate temperature solid oxide fuel cells. This enhancement was attributed to effects at the P/R/O 2 triple phase boundary (TPB). It is important to note that -in contrast to the traditional use -here TPB does not refer to the contact of gas phase, electrode and electrolyte material, but to locations where hetero-grain boundaries of two components of the cathode material are exposed to the atmosphere. The literature approaches to investigate this ORR enhancement at P/R hetero-interfaces (additional ORR activity related to TPBs, which in this work is simply denoted as "TPB effect") can be roughly divided into local ORR activity measurements by 18 O exchange and SIMS experiments, 1-4 and integral activity measurements of macroscopic two-phase electrodes with high TPB density by impedance spectroscopy. 5-11With a local measurement, the activity of the surface at a single TPB as well as that at neighboring P and R phases (reference activities) can be determined. If sufficiently high lateral resolution and vertical sampling depth is available, the strength of the TPB effect can be quantified in terms of a TPB length specific contribution to the activity. With an integral measurement of a whole electrode which contains a large amount of P and R grains and TPBs, an average activity is measured with contributions from the grains (surfaces with effective rate constants k P (x) in P La 1-x Sr x CoO 3-δ with Sr fraction x and k R (y) in R (La 1-y Sr y ) 2 CoO 4±δ with Sr fraction y) and from TPBs, which has to be compared to an appropriate reference activity and related to the TPB density for quantification.In literature, local activity measurements were performed either on ceramic samples where P/R hetero-interfaces formed sporadically by spontaneous phase separation, 1,3 or as illustrated ...

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Kinetics of Oxygen Surface Exchange on Epitaxial Ruddlesden–Popper Phases and Correlations to First-Principles Descriptors

Cited by 57 publications

References 43 publications

Exceptional electrocatalytic oxygen evolution via tunable charge transfer interactions in La0.5Sr1.5Ni1−xFexO4±δ Ruddlesden-Popper oxides

Exceptional electrocatalytic oxygen evolution via tunable charge transfer interactions in La0.5Sr1.5Ni1−xFexO4±δ Ruddlesden-Popper oxides

Understanding and Controlling the Work Function of Perovskite Oxides Using Density Functional Theory

Oxygen Exchange Activity of La-Sr-Co-O PLD Films and Quantification of (La,Sr)CoO_3-_δ/(La,Sr)₂CoO₄₊_δ/O₂Triple Phase Boundary Activity

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Kinetics of Oxygen Surface Exchange on Epitaxial Ruddlesden–Popper Phases and Correlations to First-Principles Descriptors

Cited by 57 publications

References 43 publications

Exceptional electrocatalytic oxygen evolution via tunable charge transfer interactions in La0.5Sr1.5Ni1−xFexO4±δ Ruddlesden-Popper oxides

Exceptional electrocatalytic oxygen evolution via tunable charge transfer interactions in La0.5Sr1.5Ni1−xFexO4±δ Ruddlesden-Popper oxides

Understanding and Controlling the Work Function of Perovskite Oxides Using Density Functional Theory

Oxygen Exchange Activity of La-Sr-Co-O PLD Films and Quantification of (La,Sr)CoO3-δ/(La,Sr)2CoO4+δ/O2Triple Phase Boundary Activity

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Oxygen Exchange Activity of La-Sr-Co-O PLD Films and Quantification of (La,Sr)CoO_3-_δ/(La,Sr)₂CoO₄₊_δ/O₂Triple Phase Boundary Activity