Activation of Hidden Catalytic Sites in 2D Basal Plane via p–n Heterojunction Interface Engineering Toward Efficient Oxygen Evolution Reaction

A p–n heterojunction interfacing approach is presented to modulate the electronic structure of NiFe-LDH electrocatalyst for enhanced catalytic activity toward oxygen evolution reaction under alkaline condition. The p–n heterojunction activates the hidden catalytic sites in the basal plane of 2D NiFe-LDH nanosheets through oxidation of Ni species which ultimately facilitates the oxygen evolution reaction.

Abstract

Nonprecious metal-based 2D materials have shown promising electrocatalytic activity toward the oxygen evolution reaction (OER). However, the catalytically active sites of 2D materials are mainly presented at the edge, and most of their basal planes are still catalytically inactive, which turns into a significant drawback on the catalytic efficiency. Here, a novel p–n heterojunction strategy is suggested that generates active sites on the basal plane of 2D NiFe-layered double hydroxide (NiFe-LDH). The n-type NiFe-LDH is first grown on a nickel foam (NF) substrate, and p-type Co₃O₄ nanocubes are deposited through a simple dip-coating method to fabricate a Co₃O₄/NiFe-LDH@NF p–n heterojunction electrode. As a result, electron transfer is induced at the interface of p-type Co₃O₄ and n-type NiFe-LDH, which consequently promotes oxidation of the inert Ni²⁺ state to a more catalytically active Ni³⁺ state on the inert basal plane of NiFe-LDH. As-prepared Co₃O₄/NiFe-LDH@NF electrodes obtained enhanced OER performance showing a high current density of 100 mA cm⁻² at 1.48 V (vs RHE) which outperforms that of pristine NiFe-LDH@NF. The utilization of the p–n junction concept will disclose a new strategy for modifying the electronic structure of the catalytically inactive basal plane and stimulating its electrocatalytic activity.