title: Hydrodynamic Microgap Voltammetry under Couette Flow Conditions: Electrochemistry at a Rotating Drum in Viscous Poly(ethylene glycol).
abstract: 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=1.4×10-11m2s-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.
authors.affiliation: Department of Chemistry, University of Bath, Claverton Down, Bath BA2 7AY (UK).
authors.forename: Christopher E
authors.initials: CE
authors.lastname: Hotchen
authors.affiliation: Department of Chemical Engineering, University of Cambridge, New Museums Site, Pembroke Street, Cambridge, CB2 3RA (UK).
authors.forename: H Viet
authors.initials: HV
authors.lastname: Nguyen
authors.affiliation: Department of Chemical Engineering, University of Cambridge, New Museums Site, Pembroke Street, Cambridge, CB2 3RA (UK).
authors.forename: Adrian C
authors.initials: AC
authors.lastname: Fisher
authors.affiliation: Department of Chemistry, University of Bath, Claverton Down, Bath BA2 7AY (UK).
authors.forename: Paul E
authors.initials: PE
authors.lastname: Frith
authors.affiliation: Department of Chemistry, University of Bath, Claverton Down, Bath BA2 7AY (UK).
authors.forename: Frank
authors.initials: F
authors.lastname: Marken
keywords: electrodeposition; ferrocene; green solvent; polyethylene glycol; voltammetry