Quantifying Adsorption on Single Alumina Particles via Impact Voltammetry and Current Transient Analysis

Particle impacts are used to quantify the adsorption of catechol on single alumina particles. In these experiments, particles suspended in solution impact a microelectrode held at a suitable potential for the oxidation or reduction of the adsorbed species and the resulting current/time transient “spikes” associated with individual impacts measured. Using theory for charge diffusion over the surface of a sphere, the individual impact spikes arising from the electro-oxidation of adsorbed catechol can be modeled to derive the diffusion coefficient of charge transfer over the surface of alumina as (2.5 ± 0.5) × 10–6 cm2 s–1. The coverage of catechol on the surface of alumina is found to be (5.9 ± 1.9) × 10–10 mol cm–2.