Self-Assembly-Assisted Facile Synthesis of MoS2-Based Hybrid Tubular Nanostructures for Efficient Bifunctional Electrocatalysis

Abstract

In this work, MoS₂-based hybrid tubular nanostructures are facilely synthesized via a self-assembly-assisted process and evaluated as a bifunctional electrocatalyst for hydrogen evolution reactions (HERs) and oxygen reduction reactions (ORRs). By simply mixing the reactants under ambient conditions, (NH₄)₂MoS₄/polydopamine (PDA) hybrid nanospheres are formed. The protonated dopamine is linked to tetrahedral [MoS₄]^2- via weak N-H···S and O-H···S interactions, causing the PDA nanospheres merging together and forming nanorods under stirring-induced shear force. Moreover, the oxidative polymerization of dopamine proceeds on the surface of the nanorods, whereas it is prohibited inside the nanorods owing to lack of oxygen, leading to outward diffusion of dopamine and hence cavitation. After annealing, the tubular morphology is perfectly retained, while ultrafine MoS₂ monolayers are formed due to the confinement of the framework. Benefiting from these unique structural features, the MoS₂/C hybrid nanotubes possess abundant active sites and high surface area, as well as boost electronic and ionic transport, remarkably enhancing their electrocatalytic activities. The onset and half-wave potentials are 0.91 and 0.82 V, respectively, for ORR, close to those of Pt/C. Moreover, low onset potential and small Tafel slope are also observed for HER, demonstrating the potential of the hybrid nanotubes as a promising non-noble metal bifunctional electrocatalyst.

Keywords: dopamine; electrocatalysis; molybdenum disulfide (MoS2); nanotubes; self-assembly.