Nanoparticle–electrode collision studies: Brownian motion and the timescale of nanoparticle oxidation

A theoretical model is developed for the oxidation of a nanoparticle impinging on an electrode held at a suitably oxidising potential. The model incorporates Brownian motion to account for the experimentally observed timescale of such reactions. Comparison with a naive model neglecting Brownian motion allows the effects of nanoparticle size and the rate of electrochemical reaction to be determined. The overall rate of reaction is parameterised by an apparent electrochemical ‘velocity’ which must be <10−3 m s−1 to account for millisecond timescale amperometric events. Partial oxidation events are found to be statistically unlikely, justifying quantitative analysis of experimental results.