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. 2018 Sep 17;57(38):12285-12289.
doi: 10.1002/anie.201807798. Epub 2018 Aug 28.

Local Activities of Hydroxide and Water Determine the Operation of Silver-Based Oxygen Depolarized Cathodes

Alexander Botz  1 , Jan Clausmeyer  1 , Denis Öhl  1 , Tsvetan Tarnev  1 , David Franzen  2 , Thomas Turek  2 , Wolfgang Schuhmann  1
Affiliations

Local Activities of Hydroxide and Water Determine the Operation of Silver-Based Oxygen Depolarized Cathodes

Alexander Botz et al. Angew Chem Int Ed Engl. .

Abstract

Local ion activity changes in close proximity to the surface of an oxygen depolarized cathode (ODC) were measured by scanning electrochemical microscopy (SECM). While the operating ODC produces OH- ions and consumes O2 and H2 O through the electrocatalytic oxygen reduction reaction (ORR), local changes in the activity of OH- ions and H2 O are detected by means of a positioned Pt microelectrode serving as an SECM tip. Sensing at the Pt tip is based on the pH-dependent reduction of PtO and obviates the need for prior electrode modification steps. It can be used to evaluate the coordination numbers of OH- ions and H2 O, and the method was exploited as a novel approach of catalyst activity assessment. We show that the electrochemical reaction on highly active catalysts can have a drastic influence on the reaction environment.

Keywords: electrochemistry; gas diffusion electrodes; local ion activities; nanostructures; scanning probe microscopy.

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