Abstract
There are few mass transfer studies to nanocatalysts (1 nm ≤
dp ≤ 100 nm). We have experimentally investigated
the electrocatalytic reduction of hexacyanoferrate (III) to
hexacyanoferrate (II) on gold nanospheres. The surface flux is
insensitive to particle sizes of dp≥ 30 nm. For
particle sizes of dp < 30 nm, the flux
increases sharply with decreasing particle size. However, the measured
fluxes are one to three orders of magnitude smaller than predicted by a
purely diffusion-limited model. Using mathematical modeling, we
evaluated six mechanisms potentially affecting mass transfer to a
nanoparticle. Flux concentration due to the curvature effect and
electromigration become important below 30 nm. Stabilizing layers on the
particle also greatly influence the flux through electrosteric effects.
Brownian advection, enhanced surface reactivity, and particle
aggregation play negligible roles. Tuning the charge and the tortuosity
of the stabilizer layer to potentiate the flux may be useful in
nanosuspensions.