Reconceiving catalysis at air-water interfaces: interfacial electric fields are milder than bulk fields

The catalytic properties of water microdroplets have been widely attributed to strong interfacial electric fields, yet both their magnitude and their mechanistic role remain under intense debate. Here we combine quantum data-driven many-body molecular dynamics, ab initio re-sampling, and spatially resolved electric field evaluations to provide a rigorous assessment of electrostatics at the air-water interface. By classifying molecules through diverse and widely adopted interface definitions, we obtain field distributions directly from the electronic charge density. Contrary to the prevailing assumption, our results reveal that interfacial electric fields are systematically weaker than those in bulk water, with a reduction of ~10%. This attenuation arises primarily from density depletion near the surface, with minor contributions from changes in local partial charges. These findings challenge the widespread view that enhanced reactivity in microdroplets originates from exceptionally strong interfacial electric fields.