Triphasic 2D Materials by Vertically Stacking Laterally Heterostructured 2H-/1T′-MoS₂ on Graphene for Enhanced Photoresponse

Recently the applications of 2D materials have been broadened by engineering their mechanical, electronic, and optical properties through either lateral or vertical hybridization. Here, the successful design and fabrication of a novel triphasic 2D material by vertically stacking lateral 2H-/1T′-molybdenum disulfide (MoS₂) heterostructures on graphene with the assistance of supercritical carbon dioxide is reported. This triphasic structure is experimentally shown to significantly enhance the photocurrent densities for hydrogen evolution reactions. First-principles theoretical analyses reveal that the improved photoresponse should be ascribed to the beneficial band alignments of the triphasic heterostructure. More specifically, electrons can efficiently hop to the 1T′-MoS₂ phase via the highly conductive graphene layer as a result of their strong vertical interfacial electronic coupling. Subsequently, the electrons acquired on the 1T′-MoS₂ phase are exploited to fill the photoholes on the photoexcited 2H-MoS₂ phase through the lateral heterojunction structure, thereby suppressing the recombination process of the photoinduced charge carriers on the 2H-MoS₂ phase. This novel triphasic concept promises to open a new avenue to widen the molecular design of 2D hybrid materials for photonics-based energy conversion applications.