Investigations on Structural, Electronic and Optical Properties of MoS2/CDs Heterostructure via First-Principles Study

Much effort has been made for MoS2/CDs heterostructure application in the field of photocatalysts. However, the impacts of functional groups of CDs on the properties of the heterostructure are ambiguous. Here, the impacts of hydroxyl, carbonyl, and carboxyl groups of CDs on the structural, electronic, and optical properties of MoS2/CDs' heterostructure were investigated by conducting a first-principles study. The calculated energy band structure and band gap of monolayer MoS2 were consistent with the experimental values. The band gap of MoS2 was obviously decreased after the construction of MoS2/CDs and MoS2/CDs-hydroxyl/carboxyl, thus helping to improve the light adsorption range. However, the band gap of MoS2/CDs-carbonyl was slightly increased compared with that of monolayer MoS2. The CDs with functional groups can spontaneously bind on 2D-MoS2 and form a stable MoS2/CDs heterostructure. It was confirmed that the MoS2/CDs' heterostructure belongs to the typical type-II band alignment, which contributes to the separation of photogenerated charge and hole. Notably, the carbonyl and carboxyl groups on the CDs obviously reduced the optical absorption intensity of the MoS2/CDs in the ultraviolet region. The hydroxyl groups have little effect on optical absorption intensity. Thus, the CDs with more hydroxyl groups are beneficial to produce a higher photocatalytic performance. This paper reveals the impacts of surface functional groups and provides a promising approach for designing the MoS2/CDs' heterostructure to enhance the photocatalytic properties.