Concentrated Zwitterion Interfaces for Selective Promotion of Electrochemical Hydroxide Oxidation

The electrode/electrolyte interfacial structure is a seminal component that governs the activity of electrocatalytic water splitting, providing alternative approaches to electrocatalyst design. Herein, we demonstrate that a dense interface constituting of zwitterionic betaine could selectively accelerate the alkaline oxygen evolution reaction (OER) by 2 orders of magnitude in current. The hygroscopic betaine molecules not only bind water molecules strongly but also endow the underhydrated characteristics of the hydroxide anions that increase their activity coefficient. The underhydrated hydroxide anions can also be enriched within the inner Helmholtz plane, which forms the mixed hydroxide anion-betaine adsorbate layer that significantly increases the effective potential that drives the OER. This interface can further segregate the reactive zones to selectively promote hydroxide oxidation and retard the oxidative polymerization of neutral anilines for improving the durability by at least an order of magnitude, creating new possibilities for impure water electrolysis.