Promising M 2 CO 2 /MoX 2 (M = Hf, Zr; X = S, Se, Te) Heterostructures for Multifunctional Solar Energy Applications.

Two-dimensional van der Waals (vdW) heterostructures are potential candidates for clean energy conversion materials to address the global energy crisis and environmental issues. In this work, we have comprehensively studied the geometrical, electronic, and optical properties of M 2 CO 2 /MoX 2 (M = Hf, Zr; X = S, Se, Te) vdW heterostructures, as well as their applications in the fields of photocatalytic and photovoltaic using density functional theory calculations. The lattice dynamic and thermal stabilities of designed M 2 CO 2 /MoX 2 heterostructures are confirmed. Interestingly, all the M 2 CO 2 /MoX 2 heterostructures exhibit intrinsic type-II band structure features, which effectively inhibit the electron-hole pair recombination and enhance the photocatalytic performance. Furthermore, the internal built-in electric field and high anisotropic carrier mobility can separate the photo-generated carriers efficiently. It is noted that M 2 CO 2 /MoX 2 heterostructures exhibit suitable band gaps in comparison to the M 2 CO 2 and MoX 2 monolayers, which enhance the optical-harvesting abilities in the visible and ultraviolet light zones. Zr 2 CO 2 /MoSe 2 and Hf 2 CO 2 /MoSe 2 heterostructures possess suitable band edge positions to provide the competent driving force for water splitting as photocatalysts. In addition, Hf 2 CO 2 /MoS 2 and Zr 2 CO 2 /MoS 2 heterostructures deliver a power conversion efficiency of 19.75% and 17.13% for solar cell applications, respectively. These results pave the way for exploring efficient MXenes/TMDCs vdW heterostructures as photocatalytic and photovoltaic materials.