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Mixed Diffusion‐Kinetic Control of H 2 O 2 Oxidation at an Oxide‐Covered Platinum Electrode in Alkaline Electrolyte: Implications for Oxygen Electroreduction Studies with a Rotating Ring Disk Electrode
Author(s) -
Szwabińska Katarzyna,
Lota Grzegorz
Publication year - 2021
Publication title -
chemelectrochem
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.182
H-Index - 59
ISSN - 2196-0216
DOI - 10.1002/celc.202001507
Subject(s) - chemistry , platinum , oxide , rotating ring disk electrode , electrolyte , diffusion , ring (chemistry) , electrochemistry , rotating disk electrode , electrode , oxygen , inorganic chemistry , analytical chemistry (journal) , catalysis , oxygen reduction reaction , organic chemistry , thermodynamics , cyclic voltammetry , physics
Abstract The rotating ring disk electrode (RRDE) with a Pt ring is widely applied for oxygen reduction reaction (ORR) studies, and it is generally believed that oxidation of H 2 O 2 at the Pt ring is controlled by diffusion. Indeed, H 2 O 2 oxidation at bare platinum is a diffusion‐controlled reaction. However, when Pt ring is held at 1.2 V RHE , it is being covered with surface oxide, and H 2 O 2 oxidation turns into a reaction under mixed diffusion‐kinetic control. We show that, for H 2 O 2 oxidation at an oxide‐covered Pt ring in 0.1 M KOH, the ratio of the empirical ring current to corresponding ring current under pure diffusion control varies monotonically with rotation rate. At 1.2 V RHE , the ratio is equal to 79.9 % and 61.4 % at 400 rpm and 2500 rpm, respectively. We demonstrate that this deviation prevents the correct diagnosis of ORR mechanism and leads to overestimated electron transfer number values. To eliminate the error in RRDE measurements, we employed a procedure based on the Koutecký‐Levich method, which, to our best knowledge, has not been reported yet.