C 7 N 6 /Sc 2 CCl 2 Weak van der Waals Heterostructure: A Promising Visible-Light-Driven Z -Scheme Water Splitting Photocatalyst with Interface Ultrafast Carrier Recombination.

Designing and characterizing high-efficiency direct Z -scheme photocatalysts both from theoretical and experimental aspects still remain a big challenge. Here, based on extensive first-principles calculations combined with excited state dynamics simulations, we report that a weak van der Waals (vdW) C 7 N 6 /Sc 2 CCl 2 heterostructure is a mediator-free direct Z -scheme photocatalyst for solar water splitting. Theoretical results clearly reveal that this heterostructure displays a nice light-harvesting performance extending to the near-infrared region. The relatively strong interfacial non-adiabatic coupling accelerates the interlayer carrier recombination in the time scale of sub-picoseconds. The well separated electrons and holes with a strong redox capacity make the hydrogen evolution reaction spontaneously occur on the C 7 N 6 surface and the oxygen evolution reaction on the Se-doped Sc 2 CCl 2 surface, respectively, when the proposed heterostructure is radiated with solar light.