Oxidation of d-glucose on single-crystal platinum electrodes: A mechanistic study

Abstract

Reaction kinetics of glucose oxidation on single-crystal platinum electrodes has a pronounced structure sensitivity. Quasi-steady-state measurements show Tafel slopes of 120 mV per decade for Pt(111), but 60 mV per decade for Pt(100). The isotope effect indicates that the first reaction step involves the oxidation of the aldehyde hydrogen atom bound to the C1 carbon atom, which is the rate-determining step for both surfaces. The reaction orders with respect to glucose are unity for Pt(111), but 0.5 (first peak) and close to zero (second peak) for Pt(100). The strongly bound intermediate on Pt(111) appears to be gluconolactone, but CO for Pt(100). The reaction mechanism for Pt(111) involving a slow first charge transfer step fits the observed kinetic parameters. Problems in determining the mechanism for Pt(100) are discussed, as well as the catalytic decomposition of glucose. Within this framework the oxidations of fructose, gluconolactone and gluconic acid were also investigated.