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

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.