Selective dissolution of A-site cations of La0.6Sr0.4Co0.8Fe0.2O3 perovskite catalysts to enhance the oxygen evolution reaction

In this study, we employ the strategy of substitution with more electronegative/acidic A-site ions in the cobalt perovskites to alter O 2p-band center, surface hydroxide affinity, and oxygen evolution reaction (OER) activity and stability in the basic electrolyte. Galvanostatically charged Bi0.2Sr0.8CoO3-δ (δ close to zero) was shown to exhibit record OER specific activity exceeding not only LaxSr1-xCoO3-δ but also charged SrCoO3-δ (δ close to zero), one of the most active oxide OER catalysts reported so far. The enhanced OER activity of charged Bi0.2Sr0.8CoO3-δ can be attributed to greater hydroxide affinity facilitating the deprotonation of surface bound intermediates due to the presence of strong Lewis acidic A-site Bi3+ ions, while the high stability can result from lowered O 2p-band center relative to the Fermi level. This work provides a novel example in the rational design of highly active oxide catalysts for OER by leveraging the inductive effect.

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Influence of Chemical Operation on the Electrocatalytic Activity of Ba0.5Sr0.5Co0.8Fe0.2O3−δ for the Oxygen Evolution Reaction

Journal of The Electrochemical Society ◽

10.1149/1945-7111/ac4299 ◽

2021 ◽

Author(s):

Yuta Inoue ◽

Yuto Miyahara ◽

Kohei Miyazaki ◽

Yasuyuki Kondo ◽

Yuko Yokoyama ◽

...

Keyword(s):

Oxygen Evolution ◽

Alkaline Solution ◽

Oxygen Evolution Reaction ◽

Time Course ◽

Potential Cycling ◽

Leaching Behavior ◽

Fundamental Understanding ◽

A Site

Abstract Ba0.5Sr0.5Co0.8Fe0.2O3−δ (BSCF) is a promising electrocatalyst for the oxygen evolution reaction (OER) in alkaline solution. The OER activities of BSCF are gradually enhanced by prolonging the duration of electrochemical operation at OER potentials, but the underlying cause is not fully understood. In this study, we investigated the role of chemical operation, equivalent to immersion in alkaline solution, in the time-course of OER enhancement of BSCF. Interestingly, the time-course OER enhancement of BSCF was promoted not only by electrochemical operation, which corresponds to potential cycling in the OER region, but also by chemical operation. In situ Raman measurements clarified that chemical operation had a lower rate of surface amorphization than electrochemical operation. On the other hand, the leaching behavior of A-site cations was comparable between chemical and electrochemical operations. Since the OER activity of BSCF was stabilized by saturating the electrolyte with Ba2+, “chemical” A-site leaching was key to inducing the time-course OER enhancement on perovskite electrocatalysts. Based on these results, we provide a fundamental understanding of the role of chemical operation in the OER properties of perovskites.

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Quantum chemistry of the oxygen evolution reaction on cobalt(ii,iii) oxide – implications for designing the optimal catalyst

Faraday Discussions ◽

10.1039/c5fd00213c ◽

2016 ◽

Vol 188 ◽

pp. 199-226 ◽

Cited By ~ 9

Author(s):

Craig P. Plaisance ◽

Karsten Reuter ◽

Rutger A. van Santen

Keyword(s):

Electronic Structure ◽

Oxygen Evolution ◽

Oxygen Evolution Reaction ◽

Active Sites ◽

Density Functional ◽

Oxidation Potential ◽

Water Addition ◽

Wide Range ◽

A Site ◽

Intrinsic Reactivity

Density functional theory is used to examine the changes in electronic structure that occur during the oxygen evolution reaction (OER) catalyzed by active sites on three different surface terminations of Co3O4. These three active sites have reactive oxo species with differing degrees of coordination by Co cations – a μ3-oxo on the (311) surface, a μ2-oxo on the (110)-A surface, and an η-oxo on the (110)-B surface. The kinetically relevant step on all surfaces over a wide range of applied potentials is the nucleophilic addition of water to the oxo, which is responsible for formation of the O–O bond. The intrinsic reactivity of a site for this step is found to increase as the coordination of the oxo decreases with the μ3-oxo on the (311) surface being the least reactive and the η-oxo on the (110)-B surface being the most reactive. A detailed analysis of the electronic changes occurring during water addition on the three sites reveals that this trend is due to both a decrease in the attractive local Madelung potential on the oxo and a decrease in electron withdrawal from the oxo by Co neighbors. Applying a similar electronic structure analysis to the oxidation steps preceding water addition in the catalytic cycle shows that analogous electronic changes occur during this process, explaining a correlation observed between the oxidation potential of a site and its intrinsic reactivity for water addition. This concept is then used to specify criteria for the design of an optimal OER catalyst at a given applied potential.

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Bismuth Substituted Strontium Cobalt Perovskites for Catalyzing Oxygen Evolution

10.26434/chemrxiv.8851802 ◽

2019 ◽

Author(s):

Denis Kuznetsov ◽

Jiayu Peng ◽

Livia Giordano ◽

Yuriy Román-Leshkov ◽

Yang Shao-Horn

Keyword(s):

Fermi Level ◽

Oxygen Evolution ◽

Oxygen Evolution Reaction ◽

Rational Design ◽

High Stability ◽

Inductive Effect ◽

Specific Activity ◽

Band Center ◽

Highly Active ◽

A Site

In this study, we employ the strategy of substitution with more electronegative/acidic A-site ions in the cobalt perovskites to alter O 2p-band center, surface hydroxide affinity, and oxygen evolution reaction (OER) activity and stability in the basic electrolyte. Galvanostatically charged Bi0.2Sr0.8CoO3-δ (δ close to zero) was shown to exhibit record OER specific activity exceeding not only LaxSr1-xCoO3-δ but also charged SrCoO3-δ (δ close to zero), one of the most active oxide OER catalysts reported so far. The enhanced OER activity of charged Bi0.2Sr0.8CoO3-δ can be attributed to greater hydroxide affinity facilitating the deprotonation of surface bound intermediates due to the presence of strong Lewis acidic A-site Bi3+ ions, while the high stability can result from lowered O 2p-band center relative to the Fermi level. This work provides a novel example in the rational design of highly active oxide catalysts for OER by leveraging the inductive effect.

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