Photocatalysts for energy conversion and production, pollutants degradation, CO2 reduction, organic synthesis, biomedical, are especially important in a renewable energy-based energy and economic landscape. Due to their larger surface area and efficient capacity to segregate photogenerated electrons and holes, 2D van der Waals (vdW) heterostructures are being investigated to overcome the critical challenge of the short lifespan of photogenerated charges. This study presents the most recent research on 2D photocatalysts, specifically vdW heterostructures, for energy conversion and production, pollutants degradation, CO2 reduction, organic synthesis, biomedical. After presenting the core concepts of the light-driven redox reaction for aforementioned applications, we address a number of interesting 2D vdW heterostructures, highlighting transition metal dichalcogenides and graphene oxide heterostructures from both theoretical and experimental perspectives. In this review, we address the prospects and difficulties within this field of study. The enhanced understanding of 2D vdW heterostructures in photocatalysis presented in this research opens up new possibilities for increasing the efficiency of hydrogen generation. The key issues and future developments in the applications of 2D/2D layered heterojunctions and heterostructures in photocatalysis are explored.