Post-activation of in situ B[sbnd]F codoped g-C3N4 for enhanced photocatalytic H2 evolution

Abstract

Porous graphitic carbon nitride polymer (p-CN-BF) with enhanced photoproduction of H2 from water was prepared by a two-step treatment process including in-situ Boron and fluorine codoping using [Emim]BF4 as dopants followed by post-calcination in air. Several techniques were employed to characterize the modified structure and elucidate the doping state of B and F. It was shown that in-situ doping method is necessary for efficient doping of heteroatoms into the molecular composition of CN. The difference of doping state of B and F was that B doping primary existing in the inside skeleton of CN, but F doping merely presents in the surface layer. The inside doped B made for the enhanced visible light absorption and the production of uniform porous structure during post-sintering process. By the synergistic effect of BF codoping and post-activation, p-CN-BF showed much enhanced photoelectron generation, transmission and separation, therefore, it performs high photocatalytic activity for H2 evolution (351 μmol h−1), which was 13 and 5 times higher than samples only modified by BF codoping (CN-BF) or post-annealing (P-CN).