Integrating multiple regulatory strategies: phase, morphology and interface engineering to construct a hierarchical Ni2P–MoS2/rGO heterostructure catalyst for efficient oxygen reduction reaction

Abstract

Two-dimensional (2D) molybdenum disulfide (MoS₂) with a large surface area and unique electronic properties has emerged as a promising noble metal-free catalyst for electrochemical energy storage/conversion applications. However, the high reaction energy barrier and sluggish oxygen reduction reaction (ORR) kinetics severely limit its application in the field of fuel cells. Herein, a hierarchical Ni₂P–MoS₂/rGO hybrid catalyst with Ni₂P nanoparticles uniformly supported on 2D layer 1T-MoS₂/rGO composite nanosheets was elaborately designed via multiple regulatory strategies. The high-content metallic phase of MoS₂ (1T-MoS₂) nanosheets (78%) vertically anchored on the reduced graphene oxide (rGO) substrate, which is conducive to increasing the exposed active edges of MoS₂ and accelerating the electron transport. Meanwhile, the interface electron coupling effect between Ni₂P and MoS₂ effectively generates numerous catalytically active centers via optimizing the electronic structure. Benefiting from the prominent synergistic effect of the phase, morphology, and interface engineering, the as-obtained Ni₂P–MoS₂/rGO hybrid demonstrates remarkable ORR catalytic activity and stability with a higher onset and half-wave potential of 0.916 V and 0.764 V, respectively, which are superior to those of the most reported MoS₂-based catalysts. The modification of Ni₂P on the 1T-MoS₂/rGO composite triggers a transformation of the reaction pathway from two-electron for 1T-MoS₂/rGO to direct four-electron, suggesting rapid reaction kinetics. The density functional theory (DFT) results further disclose that the rearrangement of the d band can be rationalized via the charge reconfiguration in the vicinity of the interfaces between Ni₂P and MoS₂, thereby greatly reducing the energy barrier of the ORR and enhancing the catalytic kinetics.