Hierarchical carbon nitride tube with oxygen doping and carbon defects promotes solar-to-hydrogen conversion
Micro-nanostructures, element doping and structure defects are three pivotal factors to determine the photocatalytic activity of graphitic carbon nitride polymer. Green and additive-free construction of the above three-in-one carbon nitride (CN) based materials is extremely challenging. Herein the target hierarchical carbon nitride tube with pipe-in-pipe double-layer and porous coral-like architecture as well as oxygen doping and carbon defects is successfully obtained via a self-templating method. Melamine is the only precursor in the whole process without invloving any harmful solvents or cross-linking agents for self-assembly with cyanuric acid, which comes from part of melamine under hydrothermal treatment. Surpassing the simple hollow carbon nitride tube, this hierarchical hollow structures, which is clearly visualized by 3D electron tomography, would offer more contact sites and build up new heterogeneous catalytic interfaces synergistically. Hence, the as-prepared photocatalyst achieves a satisfying hydrogen yield, ascribed to large surface area, short charge transfer distance, light scattering, fast mass transfer and suitable bandgap with midgap states. This eco-friendly method provides a new opportunity for designing novel micro-nanostructures with desirable performance in solar-to-chemical energy conversion.