Decoupling the roles of carbon and metal oxides on the electrocatalytic reduction of oxygen on La1−xSrxCoO3−δ perovskite composite electrodes

Perovskite oxides are active room-temperature bifunctional oxygen electrocatalysts in alkaline media, capable of performing the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) with lower combined overpotentials relative to their precious metal counterparts. However, their semicon...

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Published in:Physical chemistry chemical physics : PCCP 2019, Vol.21 (6), p.3327-3338
Main Authors: J Tyler Mefford, Kurilovich, Aleksandr A, Saunders, Jennette, Hardin, William G, Abakumov, Artem M, slund, Robin P, Bonnefont, Antoine, Dai, Sheng, Johnston, Keith P, Stevenson, Keith J
Format: Article
Language:English
Subjects:
Activated carbon
Carbon
Chemical analysis
Chemical reactions
Decoupling
Electrocatalysts
Electrochemical analysis
Hydrogen peroxide
INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
MATERIALS SCIENCE
Organic chemistry
Oxidation
Oxygen evolution reactions
Oxygen reduction reactions
Perovskites
Physical properties
Rotating disks
Thin films
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Summary:Perovskite oxides are active room-temperature bifunctional oxygen electrocatalysts in alkaline media, capable of performing the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) with lower combined overpotentials relative to their precious metal counterparts. However, their semiconducting nature necessitates the use of activated carbons as conductive supports to generate applicably relevant current densities. In efforts to advance the performance and theory of oxide electrocatalysts, the chemical and physical properties of the oxide material often take precedence over contributions from the conductive additive. In this work, we find that carbon plays an important synergistic role in improving the performance of La1−xSrxCoO3−δ (0 ≤ x ≤ 1) electrocatalysts through the activation of O2 and spillover of radical oxygen intermediates, HO2− and O2−, which is further reduced through chemical decomposition of HO2− on the perovskite surface. Through a combination of thin-film rotating disk electrochemical characterization of the hydrogen peroxide intermediate reactions (hydrogen peroxide reduction reaction (HPRR), hydrogen peroxide oxidation reaction (HPOR)) and oxygen reduction reaction (ORR), surface chemical analysis, HR-TEM, and microkinetic modeling on La1−xSrxCoO3−δ (0 ≤ x ≤ 1)/carbon (with nitrogen and non-nitrogen doped carbons) composite electrocatalysts, we deconvolute the mechanistic aspects and contributions to reactivity of the oxide and carbon support.
ISSN:1463-9076
1463-9084
DOI:10.1039/c8cp06268d