The Meniscus in SECCM: Formation, Stability, and Its Impact on Quantitative Electrochemistry

Scanning electrochemical cell microscopy (SECCM) is a pipette-based, spatially resolved electrochemical technique that enables localized measurements of interfacial reactivity on heterogeneous surfaces with micro- to nanoscale resolution. By forming a confined electrolyte meniscus between a pipette tip and a substrate, SECCM creates a movable droplet cell that provides access to local kinetics, selectivity, and structure–activity relationships that are obscured in ensemble-averaged measurements. A central requirement for quantitative SECCM is the formation of a stable and well-defined meniscus, because the droplet footprint governs the active area, mass transport pathways, current magnitude, and spatial resolution. This review focuses on SECCM cell stability as a primary determinant of data quality. We summarize the theoretical basis for steady-state transport in conical pipette geometries and highlight how droplet spreading can shift voltammetric behavior from sigmoidal to peak-shaped responses. We then discuss practical approaches to verify cell formation, including operando optical microscopy and electrochemical in situ estimation using retraction-curve analysis. Finally, we examine key factors that influence meniscus stability—electrolyte volatility, electrolyte additives, viscosity control, substrate-dependent wettability, and oil-immersed geometries—emphasizing how each strategy stabilizes the droplet while preserving intrinsic interfacial behavior. Collectively, this perspective provides a framework and practical guidance for improving reproducibility and enabling reliable, quantitative SECCM measurements across challenging materials and environments.