Facilitating interface charge transfer via constructing NiO/NiCo2O4 heterostructure for oxygen evolution reaction under alkaline conditions

Abstract

Designing high-activity electrocatalysts to enhance the slow multielectron-transfer process of the oxygen evolution reaction (OER) is of great importance for hydrogen generation. Here, we employ hydrothermal and subsequent heat-treatment strategies to acquire nanoarrays-structured NiO/NiCo₂O₄ heterojunction anchored Ni foam (NiO/NiCo₂O₄/NF) as efficient materials for catalyzing the OER in an alkaline electrolyte. Density functional theory (DFT) results demonstrate that NiO/NiCo₂O₄/NF exhibits a smaller overpotential than those of single NiO/NF and NiCo₂O₄/NF owing to interface-triggered numerous interface charge transfer. Moreover, the superior metallic characteristics of NiO/NiCo₂O₄/NF further enhance its electrochemical activity toward OER. Specifically, NiO/NiCo₂O₄/NF delivered a current density of 50 mA cm^-2 at an overpotential of 336 mV with a Tafel slope of 93.2 mV dec^-1 for the OER, which are comparable with those of commercial RuO₂ (310 mV and 68.8 mV dec^-1). Further, an overall water splitting system is preliminarily constructed via using a Pt net as cathode and NiO/NiCo₂O₄/NF as anode. The water electrolysis cell performs an operating voltage of 1.670 V at 20 mA cm^-2, which outperform the Pt net||IrO₂ couple assembled two-electrode electrolyzer (1.725 V at 20 mA cm^-2). This study proposes an efficient route to acquire multicomponent catalysts with rich interfaces for water electrolysis.

Keywords: Heterojunction; Interface charge transfer; Metallic feature; NiO/NiCo(2)O(4); Oxygen evolution reaction.