Tuning Surface Coordination Environment of Ni₃N by Fluorine Modification for Efficient Methanol Electrooxidation Assisted Hydrogen Evolution.

Abstract

Replacing the kinetically sluggish oxygen evolution reaction with the thermodynamically favorable methanol oxidation reaction (MOR) represents a promising strategy for energy-efficient hydrogen production. However, optimizing electrocatalytic performance in the coupled hydrogen evolution reaction (HER) and MOR requires precise regulation of the electrochemical coordination environment and a fundamental understanding of activity origins, posing a significant challenge. Here, a scalable strategy is developed that harnesses the high electronegativity of fluorine (F) to tailor the coordination environment of Ni₃N, enhancing HER kinetics. Concurrently, adsorbed F ions induce rapid and extensive self-reconstruction of the Ni₃N surface during MOR by dynamically modulating interfacial ion concentrations (OH⁻ and Ni species). This reconstruction enhances catalytic activity and enables the selective oxidation of methanol to formate via a sequential pathway, involving primary O-H bond activation followed by subsequent C-H bond cleavage at Ni active sites. Consequently, F₁₀-Ni₃N demonstrates exceptional bifunctional performance, delivering 2.02 V and remarkable stability (600 h) for MOR-coupled hydrogen production in a membrane electrode assembly-based flow electrolyzer at an industrially relevant current density of 200 mA cm^-2. This work establishes a dual-regulation paradigm for electrocatalysts, offering mechanistic insights into surface reconstruction and a rational design framework for next-generation energy conversion systems.