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Coulometric Titration of Active Sites at Mesostructured Cobalt Oxide Spinel by Surface Interrogation Mode of Scanning Electrochemical Microscopy

Lorenz, Julian and Yu, Mingquan and Tüysüz, Harun and Harms, Corinna and Dyck, Alexander and Wittstock, Gunther (2020) Coulometric Titration of Active Sites at Mesostructured Cobalt Oxide Spinel by Surface Interrogation Mode of Scanning Electrochemical Microscopy. Journal of Physical Chemistry C, 124 (14), pp. 7737-7748. ACS Publications. doi: 10.1021/acs.jpcc.9b11114. ISSN 1932-7447.

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Official URL: https://pubs.acs.org/doi/10.1021/acs.jpcc.9b11114


Cobalt-based transition-metal oxides are promising candidates for the oxygen evolution reaction (OER). However, a complex interplay between the catalyst crystal structures and material morphologies as well as the surface reactions hampers a comprehensive understanding of the electrocatalytic OER at those materials. Here, we investigate the amount and reactivity of specific surface sites of a mesostructured cobalt oxide spinel powder by surface interrogation mode of scanning electrochemical microscopy (SI-SECM). The powder material was supplied in cavity microelectrodes and efficiently titrated with an Fe(II)-triethanolamine redox mediator generated at a gold microelectrode in an alkaline electrolyte. Thus, quantification of different surface sites was achieved, and their reactivity showed dependence on the cobalt oxidation state. Titration experiments after adjustable time delays with respect to the generation of the different surface sites indicated that these surface sites are active for the OER. Kinetic analysis revealed two pseudo-first-order decay constants that were related to fast and slow surface sites for the OER. Rate constants were determined for potentials where predominantly a mixed-valence CoIII/IV state might be present as the most active species. These results expand the great potential of the surface interrogation mode on studying the reaction kinetics of distinct surface sites for practically relevant powdered, nonprecious metal catalysts to address a highly relevant challenge in electrocatalysis.

Item URL in elib:https://elib.dlr.de/134664/
Document Type:Article
Title:Coulometric Titration of Active Sites at Mesostructured Cobalt Oxide Spinel by Surface Interrogation Mode of Scanning Electrochemical Microscopy
AuthorsInstitution or Email of AuthorsAuthor's ORCID iD
Lorenz, Julianjulian.lorenz (at) dlr.dehttps://orcid.org/0000-0002-9936-7667
Yu, Mingquanyu (at) mpi-muelheim.mpg.dehttps://orcid.org/0000-0001-5825-5370
Tüysüz, Haruntueysuez (at) mpi-muelheim.mgp.dehttps://orcid.org/0000-0001-8552-7028
Harms, Corinnacorinna.harms (at) dlr.dehttps://orcid.org/0000-0001-5916-3224
Dyck, Alexanderalexander.dyck (at) dlr.dehttps://orcid.org/0000-0002-5010-8226
Wittstock, Guntherwittstock (at) uol.dehttps://orcid.org/0000-0002-6884-5515
Date:15 March 2020
Journal or Publication Title:Journal of Physical Chemistry C
Refereed publication:Yes
Open Access:Yes
Gold Open Access:No
In ISI Web of Science:Yes
DOI :10.1021/acs.jpcc.9b11114
Page Range:pp. 7737-7748
Publisher:ACS Publications
Keywords:surface interrogation mode of scanning electrochemical microscopy, surface sites, cobalt oxide spinel, coulometric titration, OER, reaction kinetics
HGF - Research field:Energy
HGF - Program:Technology, Innovation and Society
HGF - Program Themes:Renewable Energy and Material Resources for Sustainable Futures - Integrating at Different Scales
DLR - Research area:Energy
DLR - Program:E SY - Energy Systems Analysis
DLR - Research theme (Project):E - Energy Systems Technology (old)
Location: Oldenburg
Institutes and Institutions:Institute of Networked Energy Systems > Fuel Cells
Deposited By: Lorenz, Julian
Deposited On:25 May 2020 10:33
Last Modified:16 Mar 2021 03:00

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