In operando studies of heterogenous active sites using Scanning Electrochemical Microscopy (SECM) can be hindered by non-planar active sites interacting with non-apex portions of the SECM electrode tip. Concentration field distortion can result from surface sites approaching the tip size. We aim to remove these effects via finite-element modeling for a higher-fidelity depiction of surrounding concentration fields.

Experimental concentration fields near ~100 nm Pt nanoparticles are compared to a parallel, steady-state model of the identical system at varying tip-surface separations to extract kinetic and transport parameters, the concentration profile surrounding the particle, and the effective tip radius in relation to tip-surface separation. Differences between the model based on the tip presence is used to correct the experimental data for the presence of the tip.

This approach increases the measurement quality of SECM and improves understanding of heterogeneous reaction mechanisms.