Abstract
Recently the applications of two-dimensional (2D) materials have been broadened by engineering their mechanical, electronic, and optical properties through either lateral or vertical hybridization. Along with this line, we report 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. 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 photo-excited 2H-MoS2 phase through the lateral heterojunction structure, thereby suppressing the recombination process of the photo-induced 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.
