From electrostatics to electrochemistry: rethinking volta potential in nowadays and future in-situ kelvin probe studies

The Volta potential (also known as contact potential) is widely used in Kelvin probe studies of corrosion, energy materials, and biomaterials, but its relation to electrochemical behavior in solution, and its possible interpretation as an electrochemical signal, remains debated and is often inconsistent. Here, we clarify the conditions under which the electrostatic contrast revealed by Kelvin probe measurements can be meaningfully correlated with redox-related behavior, and when such interpretation is not valid. We also argue for terminology that is consistent with physical theory, interfacial chemistry, and recent methodological advances such as alternating current Kelvin probe force microscopy (AC-KPFM) and open-loop electric potential microscopy (OL-EPM).