Tuning Proton Exchange and Transport in Protic Ionic Liquid Solution through Anion Chemistry

Herein, we demonstrate that the potential difference of proton reduction and hydrogen gas oxidation of protic ionic liquids is closely related to the proton exchange rate in the electrolyte. Through a careful design of anion chemistry, the proton exchange rate can be boosted by several orders of magnitude, reaching 200 kHz at 100 °C. It is found that the enhanced proton exchange rate can effectively decrease the potential loss at the electrode, most likely through alleviating the H⁺ concentration gradient incurred by electrochemical reactions at the electrode surfaces. This research therefore highlights the strategy of using anions of medium-strength acids, such as H₂PO₄^-, for protic ionic liquids with enhanced proton exchange capability.