Scanning electrochemical cell microscopy (SECCM) is used to map anodic and cathodic processes on polycrystalline zinc in 10 mM H2SO4, at the nanoscale. Electrochemical maps are correlated directly with structural data from electron backscatter diffraction applied to the same regions of the surface, and density functional theory (DFT) calculations are used to rationalize the data. Preliminary data on droplet stability with SECCM point measurements indicated that there was a significant spreading of the meniscus cell with an air atmosphere, attributed to changes in pH during the oxygen reduction reaction, compromising the lateral resolution of the SECCM measurement. Experiments with an argon atmosphere, as well as the application of a hydrophobic n-dodecane oil layer on the Zn interface, prevented spreading. Electrochemical maps of polycrystalline Zn surface under an Ar atmosphere indicated that the hydrogen evolution reaction (HER) and Zn electrodissolution on individual low-index grains decreased in the order 1 ¯ 2 1 ¯ 0 ≥ 01 1 ¯ 0 > 0001 . DFT calculations revealed a correlation between experimental values of current associated with HER and Zn dissolution reactions and the predicted hydrogen adsorption and Zn dissolution energies on individual facets, respectively. This work further advances SECCM as a technique for probing electrified interfaces and demonstrates its applicability to reactive metals.

Probing Cu corrosion in an aqueous nanodroplet/oil/metal three-phase environment revealed unique patterns of surface reactivity. The electrochemistry of high-index facets cannot be predicted simply from the low-index {001}, {011} and {111} responses.

The redox activity (Li‐ion intercalation/deintercalation) of a series of individual LiMn2O4 particles of known geometry and (nano)structure, within an array, is determined using a correlative electrochemical microscopy strategy. Cyclic voltammetry (current–voltage curve, I–E) and galvanostatic charge/discharge (voltage–time curve, E–t) are applied at the single particle level, using scanning electrochemical cell microscopy (SECCM), together with co‐location scanning electron microscopy that enables the corresponding particle size, morphology, crystallinity, and other factors to be visualized. This study identifies a wide spectrum of activity of nominally similar particles and highlights how subtle changes in particle form can greatly impact electrochemical properties. SECCM is well‐suited for assessing single particles and constitutes a combinatorial method that will enable the rational design and optimization of battery electrode materials.