Mapping Electroactivity at Individual Catalytic Nanostructures Using High-Resolution Scanning Electrochemical–Scanning Ion Conductance Microcopy

Combined scanning electrochemical–scanning ion conductance microcopy (SECM–SICM) has been used to map the electroactivity of surfaces decorated with individual features at the 100–150 nm scale. Dual channel capillary probes consisting of an open SICM barrel, and a solid carbon SECM electrode enabled correlation of surface activity with accurate topographical information. Measurements were validated by approach curve analysis and imaging of model systems in feedback and substrate generation–tip collection modes and then applied to the examination of two nanostructured test substrates. First, electronically isolated gold nanodisk arrays were imaged using a simple electrochemical redox mediator, in which a clear positive feedback signal was observed at the SECM electrode, and the topographical channel compared well with AFM imaging. Second, platinum nanosphere ensembles were mapped using platinum-modified carbon probes to detect oxygen consumption in a redox competition mode, demonstrating the means to study electrocatalytic processes at individual nanoparticles. This work demonstrates the value of high-resolution SECM–SICM for low-current amperometric imaging of nanosystems, and is a step toward quantitative measurement of electrokinetics at the single particle level.