Confinement Improves Mass Transfer and Chemical Reactivity in Electrified Membranes for Micropollutant Degradation

Abstract Micropollutants (MPs) pose a significant threat to global water environments, necessitating advanced treatment technologies. Distributed electrochemical systems utilizing electrified membranes (EMs) show promise but face challenges due to unclear mass transfer and reaction mechanisms within membrane pores of varying sizes and surface chemistry. This review examines the interplay between spatial confinement, mass transfer, and chemical reactions in EMs, focusing on reactive species (RSs), the EM‐MPs system evolution, and mass transfer phenomena across pore sizes from microns to sub‐nanometer scales. Despite advances in RS research, a coherent mechanistic understanding of MP degradation under spatial confinement remains elusive, particularly under extreme confinement where mass transfer and reactions deviate from bulk behavior. Gaps in knowledge stem from complex mass transfer dynamics, chemical reaction thermodynamics and kinetics, and the need for detailed theoretical understanding to describe confinement effects. This review summarizes the generation mechanisms and detection methods for RSs, outlines progress in EM operational modes, and elucidates how spatial confinement impacts both mass transfer and chemical reactions. Future research shall focus on the precise identification and quantitative regulation of RSs, optimization of mass transfer processes in relation to RSs and MPs, and investigation of active sites and energetic barriers in confined environments.