In situfabrication of hierarchically porous g-C3N4 and understanding on its enhanced photocatalytic activity based on energy absorption

A novel strategy is proposed to in situ synthesize hierarchically porous g-C3N4 foam (FCN) with no carbon residue by low-cost polyurethane sponge as single template. The porous system consists of interconnected micron (1-2 mu m) and nano-scale (20-80 nm) pores, which is usually constructed tediously. For visible light catalysis, the FCN with unique hierarchical pores possesses higher efficiency for H-2 generation (8 times) and phenol degradation (4 times) over pristine g-C3N4 due to the increased BET surface area, accelerated mass transfer and improved efficiency of exciton generation and dissociation, which all derive from the hierarchical pore system. Further, an optical simulation is initially adopted to illustrate the effect of the hierarchical porosity with micron and nano-scale pores on the ability of light absorption and penetration over FCN and an energy-absorption-based explanation is proposed to deeply explain the enhanced photocatalytic activity, which opens a window to directly understand the relationship of the enhanced photocatalytic activities and absorbed light energy increased by the hierarchical pores system.