Sulfur/phosphorus doping-mediated morphology transformation of carbon nitride from rods to porous microtubes with superior photocatalytic activity

Hetero-atoms doping or morphology controlling of carbon nitride (g-C3N4) can availably regulate its electronic band structure and optimize photocatalytic performance under visible light. Herein, sulful (S), phosphorus (P) co-doped porous carbon nitride microtubes (SPCN) was synthesized by using ammonium dihydrogen phosphate and melamine as precursors, in which ammonium dihydrogen phosphate can not only control the morphology of carbon nitride from nanorods to porous microtubes, but also provide a potential P source for P-doped CN. The prepared SPCN0.1 with the content of 0.1 g ammonium dihydrogen phosphate displayed the highest photocatalytic hydrogen generation rate of 4200.3 µmol g-1h-1, which was approximately 25 and 1.6 folds by bulk g-C3N4 (CN) and sulphur doped g-C3N4 microrods (SCN), respectively. Moreover, the apparent quantum efficiency of HER reached up to 10.3 % at 420 nm. The enhanced photocatalytic performance may be attributed to the synergistic effect of S, P doping and morphology structure of carbon nitride, which effectively accelerated the separation and transfer of photogenerated electron-hole pairs, proved by photoluminescence spectra, time-resolved PL spectra, electrochemical impedance spectrum and transient photocurrent responses. The novel synthetic method described in this paper is an effective approach to regulate the morphology of g-C3N4via non-metal doping with superior photocatalytic performance.