Electrochemical Scanning Microwave Microscopy Reveals Ion Intercalation Dynamics and Maps Active Sites in 2D Catalyst

Abstract The accelerated demand for electrochemical energy storage urges the need for new, sustainable, and lightweight materials able to store high energy densities rapidly and efficiently. Development of these functional materials requires specialized techniques that can provide a close insight into the electrochemical properties at the nanoscale. For this reason, the electrochemical scanning microwave microscopy (EC‐SMM) enabling local measurement of electrochemical properties with nanometer spatial resolution and sensitivity down to atto‐Ampere electrochemical currents is introduced. Its power is demonstrated by studying NiCo‐layered double hydroxide flakes, revealing active site locations and providing atomistic insights into the catalytic process. EC‐SMM's spatial resolution of 16 ± 1 nm allows detailed analysis of edge effects in this 2D material, including localized electrochemical impedance spectroscopy and cyclic voltammetry. Coupled with advanced numerical modeling of diffusion and migration dynamics at the material interface, the findings elucidate the previously hypothesized processes responsible for localized enhancements in electrochemical activity, while pinpointing essential parameters for tuning the thermodynamics of ion intercalation and optimizing surface adsorption.