▎ 摘　　要

Leaching of metals into the ground causes major peril to the lives of the living organisms as well as the environment. Due to this fact, non-metallic semiconductors have gained substantial interest. High chemical stability and good thermodynamic potential of graphitic carbon nitride renders it a good catalytic material for water splitting. Graphene is also an effective photocatalyst because of exclusive mechanical properties, extraordinary thermal conductivity, and high specific surface area as well as high young modulus. But high recombination rate, the low surface area beside the poor movement of the charges of graphitic carbon nitride, and zero band gap of graphene limit their application. These can be amended by forming their couple, their hybrid with other semiconductors, depositing co-catalyst, etc. This review clearly outlines the merits of forming a couple of graphitic carbon nitride or graphene and their hybrid nanostructured catalysts with other semiconductors. Methodologies of synthesis, physico-chemical characteristics, band gap features, catalytic mechanism, and their applications for photocatalytic hydrogen production are also clearly explained. The methods to amend the aforementioned drawbacks and future prospects of these metal-free flat type structured catalysts are also discussed.