Intermediate-mediated strategy to horn-like hollow mesoporous ultrathin g-C3N4 tube with spatial anisotropic charge separation for superior photocatalytic H2 evolution

Metal-free graphitic carbon nitride (g-C3N4) has triggered huge interests for converting solar energy into fuels. However, direct-calcination derived bulk g-C3N4 always suffers from low surface area and high recombination of charge carriers, prompting attempts to foster g-C3N4 nano/microstructures to achieve high performance. Conventional routes, like templating method, always yields g-C3N4 with tedious morphology and requires posttreatment. Here we release the first report on development of horn-like hollow mesoporous ultrathin (HHMU) gC(3)N(4) tubes via first forming a horn-like Br-containing intermediate followed by further decomposition transformation under co-pyrolysis of melamine and substantial NH4Br. The multiple-superiorities achieved here (hollow/mesoporous/ultrathin/horn-like) allows g-C3N4 high surface area, drastically boosted bulk charge separation, carrier density and surface charge transfer efficiency. This advanced g-C3N4 thus casts outstanding photocatalytic performance for H-2 evolution with an apparent quantum efficiency (AQE) of 14.3% at 420 +/- 15 nm, far exceeding most of reported g-C3N4. HHMU g-C3N4 also delivers a strengthened photocatalytic CO2 reduction activity into CO and CH4. Selective photo-deposition results provide an in-depth insight into charge movement behavior and high photo-reactivity that the photo-generated electrons migrate to the outer shell and holes prefer to transfer onto the inner shell of HHMU g-C3N4 tubes, thus achieving efficient spatial anisotropic charge separation. The current study may furnish a reference towards developing efficient tactics for integrally advancing g-C3N4 for renewable energy generation, and disclose a new perspective into promoting charge separation via microstructure design.