Applications of Nanoscale Electrochemical Characterization Techniques in the Oxygen Evolution Reaction.

Water electrolysis provides a sustainable route for hydrogen production, yet its overall efficiency is largely constrained by the sluggish kinetics of the oxygen evolution reaction (OER). Although substantial progress has been achieved in improving the activity and stability of OER electrocatalysts, the interfacial origins of catalytic performance remain insufficiently understood. Under operating conditions, OER catalysts are not static materials; their active sites, local chemical environments, and surface structures evolve dynamically at nanometer length scales. Such nanoscale heterogeneity is often obscured by ensemble-averaged measurements, making it difficult to correlate local reaction events with macroscopic catalytic behavior. The central challenge, therefore, is to determine how site-specific activity, intermediate evolution and structural reconstruction collectively govern OER kinetics. Here, we show that nanoscale electrochemical characterization provides a powerful framework for addressing this challenge. This Review summarizes how localized electrochemical probing, optical and spectroelectrochemical imaging, and in situ scanning probe methods resolve activity distributions, transient chemical information, and catalyst reconstruction during OER. These approaches move OER analysis beyond averaged descriptors by directly linking local interfacial processes to catalyst function. Future advances in multimodal integration, data-driven analysis, micro-/nanofluidic regulation, and durable probe materials are expected to promote more quantitative, operando, and engineering-relevant OER characterization.