Stable and Contamination-Resistant Ag/Ag₂O Micro-Reference Electrode for Alkaline Scanning Electrochemical Cell Microscopy

Reliable reference electrodes (REs) with long-term stability and contamination resistance are essential for accurate electrochemical measurements. The ongoing miniaturization of electrochemical systems creates a growing demand for micro-REs that are compatible with confined electrochemical cells. However, fabricating miniaturized REs that exhibit minimal potential drift and avoid electrolyte contamination, particularly in alkaline media, remains challenging. Here, using scanning electrochemical cell microscopy (SECCM) as a model platform, we systematically investigate the failure mechanisms of conventional micro-Ag/AgCl and micro-Ag/Ag2O REs in alkaline electrolytes, revealing interference from Ag(OH)2– contamination and accelerated fouling caused by Ag2O exfoliation. To overcome these limitations, we developed protected Ag/Ag2O micro-REs via Nafion coating and polypropylene tube encapsulation. The resulting REs exhibit excellent potential stability (<0.2 mV/h drift) and contamination resistance (>3 h) in alkaline SECCM measurements. We further demonstrate their utility by probing Fe incorporation effects in β-Co(OH)2 microplatelets at the single-particle level, quantitatively revealing facet-dependent Fe doping behavior and the resulting enhancement in electrocatalytic oxygen evolution activity. This work establishes a stable and contamination-resistant micro-RE platform in alkaline environments, enabling reliable electrochemical measurements in advanced in situ characterization techniques employing miniature electrochemical systems.