Ionic Liquid Enhanced Proton Transfer for Neutral Oxygen Evolution Reaction

The development of highly active catalyst in pH-neutral media for oxygen evolution reaction (OER) is critical in the field of renewable energy storage and conversion. Nevertheless, the slow kinetics of proton-coupled electron transfer (PCET) hinders the overall OER efficiency. Herein, we report an ionic liquid (IL) modified CoSn(OH)₆ nanocubes (denoted as CoSn(OH)₆-IL), which could be prepared through a facile strategy. The modified IL would not change the structural characteristics of CoSn(OH)₆, but could effectively regulate the local proton activity near the active sites. The CoSn(OH)₆-IL exhibited higher intrinsic OER performances than the pristine CoSn(OH)₆ in neutral media. For example, the current density of CoSn(OH)₆-IL at 1.8 V versus reversible hydrogen electrode (RHE) was about 4 times higher than that of CoSn(OH)₆. According to the pH-dependent kinetic investigations, operando electrochemical impedance spectroscopic, chemical probe tests, and deuterium kinetic isotope effects, the interfacial layer of IL could be utilized as a proton transfer mediator to promote the proton transfer, which enhances the surface coverage of OER intermediates and reduces the activation barrier. Consequently, the sluggish OER kinetics would be efficiently accelerated. This study provides a facile and effective strategy to facilitate the PCET processes and is beneficial to guide the rational design of OER electrocatalysts.