Dual Polarization of Ni Sites at VOx-Ni3N Interface Boosts Ethanol Oxidation Reaction

Abstract

Substituting thermodynamically favorable ethanol oxidation reaction (EOR) for oxygen evolution reaction (OER) engenders high-efficiency hydrogen production and generates high value-added products as well. However, the main obstacles have been the low activity and the absence of an explicit catalytic mechanism. Herein, a heterostructure composed of amorphous vanadium oxide and crystalline nickel nitride (VO_x-Ni₃N) is developed. The heterostructure immensely boosts the EOR process, achieving the current density of 50 mA cm^-2 at the low potential of 1.38 V versus reversible hydrogen electrode (RHE), far surpassing the sluggish OER (1.65 V vs RHE). Electrochemical impedance spectroscopy indicates that the as-fabricated heterostructure can promote the adsorption of OH^- and the generation of the reactive species (O^*). Theoretical calculations further outline the dual polarization of the Ni site at the interface, specifically the asymmetric charge redistribution (interfacial polarization) and in-plane polarization. Consequently, the dual polarization modulates the d-band center, which in turn regulates the adsorption/desorption strength of key reaction intermediates, thereby facilitating the entire EOR process. Moreover, a VO_x-Ni₃N-based electrolyzer, coupling hydrogen evolution reaction (HER) and EOR, attains 50 mA cm^-2 at a low cell voltage of ≈1.5 V. This work thus paves the way for creating dual polarization through interface engineering toward broad catalysis.

Keywords: dual polarization; ethanol oxidation reaction; interface engineering; nickel nitride; vanadium oxide.