Activation of Hidden Catalytic Sites in 2D Basal Plane via p-n Heterojunction Interface Engineering Toward Efficient 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.