Considerations for Spatially Resolved Tafel Analysis at Electrocatalytic Interfaces Using Scanning Electrochemical Cell Microscopy

Tafel analysis is a cornerstone of electrocatalyst research, providing mechanistic and kinetic information from current–potential measurements. However, its application has largely been restricted to macroscopic electrochemical measurements, limiting its use for heterogeneous electrode surfaces. Scanning electrochemical cell microscopy (SECCM) offers the spatial resolution necessary to perform local Tafel analysis, but its compatibility with the experimental conditions typically employed for reliable, high-throughput SECCM measurements has not been systematically explored. Here, the acidic hydrogen evolution reaction (HER) on polycrystalline platinum and gold is used as a model system to establish practical guidelines for performing Tafel analysis by SECCM. By systematically examining the effects of probe size, voltammetric scan rate, and electrochemical surface conditioning, it is shown that individual (i.e., spatially resolved) Tafel analyses can be completed in a matter of seconds, irrespective of probe size, provided sufficiently slow voltammetric scan rates and appropriate electrochemical preconditioning are employed. The resulting methodology is demonstrated through high-throughput SECCM mapping of the HER on polycrystalline gold over a 180 × 180 μm2 area containing over 2000 individual measurements. The measured Tafel slope and exchange current densities are consistent with established macroscopic behavior while providing direct, spatially resolved access to individual crystallographic facets. This methodology extends conventional macroscopic Tafel analysis to heterogeneous electrode surfaces, enabling high-throughput mapping of local Tafel parameters.