Facilitating Electrochemical Overall Water Splitting Through Tailoring Halloysite Nanoclay-Based Nanoarchitectonics of Ionic Environment and Gas-Bubble Wettability.

Abstract

Unwanted gas bubble adhesion at the electrode surface and its unfavorable microenvironment compromise water splitting performance by perturbing the access of electrolytes and electron transfer processes. While reported bubble-repellent coatings promote an early detachment of gas bubbles-they mostly fail to provide a favorable ionic microenvironment for overall electrochemical water-splitting. Here, it has experimentally and theoretically validated the impact of the synergistic association of bubble repellence and selective ionic environments on water splitting performance. Halloysite nanoclay-based coating with tailored ionic environment and gas-bubble wettability on nickel foam (NF) ensured a superior performance for hydrogen and oxygen evolution reactions (HER and OER) in alkaline medium (1 M KOH). Superaerophobic coatings on NF with cationic modifiers boost HER by polarizing water around the electrode surface, and anionic modifiers improve OER via facilitating OH^- availability, leading to 42% and 30% lower overpotentials at a current density of 100 mA cm^-2, respectively. Eventually, it improves gas production by >60% compared to bare NF in alkaline conditions at a given potential. This strategy lowers the cell voltage required for overall water splitting by 500 ± 6 mV while sustaining a current density of 100 mA cm^-2.