Improved charge transport through 2D framework in fully condensed carbon nitride for efficient photocatalytic hydrogen production

The 1D molecular structure of traditional graphitic carbon nitride (GCN) leads to the space-confined transport of charge carriers along the chains and prohibits transport across the chains. Therefore, the formation of 2D network which can provide more convenient transfer paths is of great desirable. In this work, a fully condensed carbon nitride with the real 2D framework was successfully developed by post-calcining 1D GCN in a LiCl/KCl molten salt. The newly formed 2D molecular structure significantly promoted the charge transfer and separation, resulting in remarkably enhanced photocatalytic hydrogen production activity. Moreover, N-doped graphene quantum dots (NGQDs) incorporation can be simultaneously realized via the simple one step “co-dissolution and recrystallization” method. Especially, the as-prepared 2D-CN/NGQDs sample presents a further increased photocatalytic hydrogen evolution rate up to about 30 times that of pristine GCN. The apparent quantum efficiency (AQE) for H2 evolution of 2D-CN/NGQDs reaches 36 % at 420 nm.