Regulating novel electrochemical reactions through transport processes and confinement effects

Achieving high selectivity remains a central challenge in electrosynthesis, particularly as the field advances toward increasingly complex and value-added chemical transformations. Beyond catalyst design, electrochemical parameters, and reaction medium engineering, reaction pathways and selectivity are fundamentally shaped by the dynamic interfacial microenvironment, where reactive species exhibit fluxes, distributions, residence times, and local organization distinct from those in the bulk phase. In this context, transport regulation and confinement effects represent two complementary dimensions for steering electrosynthesis selectivity. Transport regulation primarily acts through the modulation of species fluxes, concentration gradients, and local acid-base balance within the diffusion layer and near-electrode region, whereas confinement effects arise in restricted micro- and nanoscale domains that reorganize solvation, ion pairing, local electric fields, and intermediate stabilization. This review establishes a multiscale framework for understanding selective electrosynthesis through these complementary interfacial dimensions. We highlight the governing principles, advanced in situ and operando tools for probing interfacial phenomena, representative regulation strategies, and the major challenges in building predictive links between interfacial descriptors and reaction outcomes. By integrating these perspectives, this review aims to advance electrosynthesis from empirical optimization toward mechanism-guided design and more reliable translation to practical synthesis.