Co-MOF-derived core–shell CoP@Co3O4 nanoparticle loaded N-doped graphene: an efficient catalyst for the oxygen evolution reaction†

Abstract

Metal–organic frameworks (MOFs) and their derivatives have multiple advantages, such as controlled morphology and uniform distribution of elements, and can serve as a kind of excellent electrocatalyst. It is significant to balance the relationship between activity, conductivity and stability of catalysts for the oxygen evolution reaction (OER). The construction of an interface in composite materials is an important strategy for the preparation of catalysts for the OER. In this paper, a novel Co-MOF (Co-MOF-NH₂) was synthesized by a hydrothermal method, and was mixed with melamine phosphate (P-MA) and calcined to obtain an AIP-PMA composite material. For the first time, a one-step pyrolysis method was used to embed CoP nanoparticles into the Co₃O₄ shell and load them on the N-doped graphene layer. As a result, the unique morphology offered more dispersed active sites and larger specific surface area, and exhibited the highest catalytic activity and electrical conductivity. Density functional theory (DFT) calculation also showed that the formation of the interface between CoP and Co₃O₄ made the center of the d band of Co in AIP-PMA locate far from the Fermi level, thus reducing the energy barrier for O₂ release and resulting in excellent OER performance with a 1.55 V potential at a current density of 10 mA cm⁻². Furthermore, the graphene coating effectively shielded the catalyst, allowing it to remain stable over time.