Characterisation of the sonicated ring-pellet reactor and sono-ring-disc electrodes

Collection efficiency measurements are presented for a range of sonicated r ing-disc electrodes. Complementary measurements of transient current result ing from a potential step at the disc are reported, showing rapid transport from disc to ring, resulting in steady state limiting currents being estab lished in under 50 ms. Comparisons are made with the slower transport in th e conventional rotating ring-disc electrode system. The methodology is appl ied to a novel sono-ring-pellet reactor, where the disc is replaced with a pellet of solid material. The dissolution of p-chloranil in aqueous media i s used as a model system. Dissolution fluxes and heterogeneous rate constan ts evaluated from this data are in excellent agreement with previously repo rted independently determined values. Shortlived intermediate species which are electrochemically invisible in conventional rotating ring-pellet exper iments are fully visible and quantifiable in the sono-ring-pellet reactor o wing to the much reduced transit times between pellet/disc and ring. (C) 20 01 Elsevier Science B.V. All rights reserved.