Theory of coupled ion-electron transfer kinetics

The microscopic theory of chemical reactions is based on transition state theory, where atoms or ions transfer classically over an energy barrier, as electrons maintain their ground state. Electron fundamentally different and occurs by tunneling in response to solvent fluctuations. Here, we develop the coupled ion-electron transfer, which molecules fluctuate cooperatively facilitate non-adiabatic electron transfer. We derive a general formula reaction rate that depends overpotential, properties, electronic structure donor/acceptor, excess potential For Faradaic reactions, predicts curved Tafel plots with concentration-dependent reaction-limited current. moderate overpotentials, our reduces Butler–Volmer equation explains its relevance, not only well-known limit large electron-transfer (solvent reorganization) energy, but also opposite ion-transfer energy. applied Li-ion batteries, reduction electrode host material couples ion insertion. In case lithium iron phosphate, accurately concentration dependence exchange current measured operando X-Ray microscopy without any adjustable parameters. These results pave way for interfacial engineering enhance intercalation rates, ionic separations neuromorphic computing.