Hidden interfacial electric fields in chemistry: contact electrification and beyond

A wide range of chemical transformations proceed at immiscible boundaries, including solid dielectric-liquid, gas-liquid, and liquid-liquid interfaces, even in the absence of light, heat or externally applied potentials. At these boundaries, intense interfacial electric fields emerging from interfacial charge transfer, molecular orientation, and asymmetric charge distributions can profoundly reshape reaction free-energy landscapes. Especially at solid dielectric-liquid interfaces, contact electrification (CE) mainly drives electron transfer, generating substantial surface charge densities and interfacial electric fields that critically govern radical formation and redox chemistry. Gas-liquid or immiscible liquid-liquid interfaces, exemplified by microdroplet reactions, as well as processes at biomolecular condensate-solution boundaries, exhibit intrinsic fields on the order of ∼10⁶-10⁹ V m^-1. Notwithstanding the burgeoning interest in this area, further fundamental scrutiny is necessary to establish a unified conceptual framework for interfacial electric field-driven reactions, moving beyond empirical observations toward predictive control. In this review, interfacial electric fields are described as emerging from cooperative effects, including CE, oriented water dipoles and ion redistribution, while their dynamic fluctuations are highlighted as a critical factor in driving interfacial chemical reactions. Mechanical excitation, material electronegativity, solvent structure, ionic strength, pH and dissolved gases are discussed as key parameters that modulate these fields and the resulting reactivity. We further emphasize some open questions concerning their spatial distribution, temporal dynamics and reaction-driven evolution and highlight the need for advanced operando techniques capable of resolving interfacial electric fields with nanometer spatial resolution and sub-microsecond temporal resolution to establish causal links between electric field dynamics and reaction outcomes. Overall, interfacial electric fields emerge as hidden forces with far-reaching implications and should be elevated from passive boundary conditions to explicit design parameters for sustainable, high-efficiency interfacial chemistry.