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 (VOx-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 VOx-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.