Interfacial Lithium Cations Catalyze Biomimetic Aerobic Oxygenation via Short-Range Electrostatic Interaction

Abstract

Enzymes often involve short-range electrostatic interactions in the deliberate microenvironment for accelerating the catalysis. Comparatively, electrostatic interactions from ions in solutions are mostly shielded by solvent or counter-ion shells, creating negligible catalytic effects. Herein, we discovered that the interfacial Li+ cations accumulated on electrodes catalyze the selective water-involved O2 electro-reduction into peroxide anion (OOH-), forming an active side-on Li+-OOH- complex via short-range electrostatic interaction. This complex reduces the O2 reduction energy barrier and increases the nucleophilicity, expediting the aerobic oxygenation of ketones. Aside from trapping active intermediates, Li+ cations also attract the excessive water dipoles to prevent from quenching the active Li+-OOH- complex. By using probe-assisted quantitative methods, we demonstrated the unique under-coordinative characteristics of interfacial Li+ for interacting with reaction intermediates, and the effective concentration of under-coordinative Li+ on the interface is an order of magnitude higher than in the bulk solution. These analyses provide essential evidences about the intrinsic difference between bulk ions and interfacial ions toward catalysis.