Interaction of Overlimiting-Current Mechanisms with Reaction Limitations

Determine how electroosmotic flow, electroosmotic instability, charge regulation, and water splitting interact with reaction limitations in charged porous media, and whether enhancing these mechanisms can enable overlimiting currents for systems with intrinsically slow reaction kinetics.

Background

The paper’s quantitative theory focuses on surface conduction as the mechanism by which negatively charged porous media sustain overlimiting currents. It explicitly notes that other physical and chemical mechanisms—including electroosmotic flow, electroosmotic instability, charge regulation, and water splitting—can also produce overlimiting current, particularly in systems with larger pores, bare electrodes, or strong pH gradients coupled to Faradaic reactions.

The unresolved issue is whether these mechanisms interact with reaction limitations in a manner analogous to surface conduction and whether strengthening them can overcome intrinsically slow interfacial kinetics. Resolving this question would extend the model beyond its present surface-conduction-only treatment and help establish whether reaction-limited overlimiting behavior is a general feature of other overlimiting-current mechanisms.