Direct Z-scheme photocatalytic systems based on vdW heterostructures for water splitting and CO2 reduction: fundamentals and recent advances

Photocatalytic water splitting and CO2 reduction are conducive to alleviating the increasingly serious environmental problems and ever-tightening energy problems. Among various modification strategies, constructing Z-scheme heterostructures and direct Z-scheme heterostructures, in particular, by mimicking natural photosynthesis, has been widely researched for the effective separation of photogenerated electrons and holes with strong redox ability. However, a low lattice matching degree of different semiconductors often results in serious crystal defects in the composite. Fortunately, van der Waals (vdW) heterostructures constructed through interlayer weak vdW interactions provide a remedy, which not only can ensure the high quality of Z-scheme heterostructures but also preserve the original properties of individual components and induces new properties at the heterogeneous interfaces. Herein, we introduce the fundamentals of direct Z-scheme vdW heterostructure and review the last five-year progress of direct Z-scheme vdW heterostructures for photocatalytic water splitting and CO2 reduction, highlighting the characteristics and fundamental modification principles of different heterostructures, aiming to provide informative principles for the design of advanced heterostructure photocatalysts for solar energy conversion.