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Hydrodynamic Microgap Voltammetry under Couette Flow Conditions: Electrochemistry at a Rotating Drum in Viscous Poly(ethylene glycol)
Author(s) -
Hotchen Christopher E.,
Nguyen H. Viet,
Fisher Adrian C.,
Frith Paul E.,
Marken Frank
Publication year - 2015
Publication title -
chemphyschem
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.016
H-Index - 140
eISSN - 1439-7641
pISSN - 1439-4235
DOI - 10.1002/cphc.201500408
Subject(s) - ethylene glycol , couette flow , diffusion , linear sweep voltammetry , electrochemistry , cyclic voltammetry , rotating disk electrode , voltammetry , materials science , viscosity , electrode , current (fluid) , ferrocene , analytical chemistry (journal) , thermodynamics , chemistry , flow (mathematics) , chemical engineering , mechanics , composite material , chromatography , organic chemistry , physics , engineering
Electrochemical processes in highly viscous media such as poly(ethylene glycol) (herein PEG200) are interesting for energy‐conversion applications, but problematic due to slow diffusion causing low current densities. Here, a hydrodynamic microgap experiment based on Couette flow is introduced for an inlaid disc electrode approaching a rotating drum. Steady‐state voltammetric currents are independent of viscosity and readily increased by two orders of magnitude with further potential to go to higher rotation rates and nanogaps. A quantitative theory is derived for the prediction of currents under high‐shear Couette flow conditions and generalised for different electrode shapes. The 1,1′‐ferrocene dimethanol redox probe in PEG200 ( D =1.4×10 −11 m 2 s −1 ) is employed and data are compared with 1) a Levich‐type equation expressing the diffusion–convection‐limited current and 2) a COMSOL simulation model providing a potential‐dependent current trace.