Potential of Zero Charge at Electrochemical Interfaces: Concepts, Measurement Strategies, and Emerging Applications

Abstract

The potential of zero charge (PZC) is a key reference potential for understanding the electrochemical double layer at electrode/electrolyte interfaces. It describes the potential at which the excess charge on the electrode side becomes zero and provides a basis for discussing interfacial electric fields, ion distributions, solvent orientation, adsorption, and charge transfer reactions. Although the PZC can be defined clearly for liquid-metal electrodes that behave close to ideally polarizable interfaces, its assignment becomes more complex for solid electrodes because surface structure, oxide formation, hydrogen and oxygenated species adsorption, and specific adsorption can contribute to the measured response. This mini-review discusses classical and modern strategies for PZC determination, including electrocapillarity, differential capacitance, immersion measurements, CO displacement, piezoelectrochemical spectroscopy, scanning electrochemical cell microscopy, phase-sensitive in situ second harmonic generation, and atomic force microscopy approaches. By comparing their principles, applicable interfaces, and limitations, this mini-review emphasizes that PZC values should be interpreted together with the electrode material, electrolyte composition, surface state, local electronic structure, spatial scale, and measurement method.