Biphasic 1T/2H-MoS₂ Nanosheets In Situ Vertically Anchored on Reduced Graphene Oxide via Covalent Coupling of the Mo–O–C Bond for Enhanced Electrocatalytic Hydrogen Evolution

Transition-metal dichalcogenides (TMDs) have recently emerged as promising electrocatalysts for the hydrogen evolution reaction owing to their tunable electronic properties. However, TMDs still encounter inherent limitations, including insufficient active sites, poor conductivity, and instability; thus, their performance breakthrough mainly depends on structural optimization in hybridization with a conductive matrix and phase modulation. Herein, a 1T/2H-MoS₂/rGO hybrid was rationally fabricated, which is characterized by biphasic 1T/2H-MoS₂ nanosheets in situ vertically anchored on reduced graphene oxide (rGO) with strong C-O-Mo covalent coupling. The rGO substrate improves the conductivity and ensures high-dispersed 1T/2H-MoS₂ nanosheets to expose plentiful highly active edges. More importantly, the strong heterointerface electrical interaction by the C-O-Mo covalent bond can enhance the charge-transfer efficiency and reinforce structural stability. Furthermore, the integration with the appropriate 2H phase is in favor of stabilization of the metastable 1T phase; thus, the ratio of 1T and 2H was precisely regulated to balance activity and stability. With these advantages, the 1T/2H-MoS₂/rGO catalyst presents a satisfactory activity and stability, as confirmed by the relatively low overpotential (268 and 140 mV at 10 mA cm^-2) and the small Tafel slope (102 and 86 mV dec^-1) in alkaline and acidic media, respectively. The theory calculations disclose that the electronic structure redistribution has been optimized via the strong coupled C-O-Mo heterointerface and phase interface, significantly reducing the adsorption free energy of hydrogen and improving intrinsic activity.