Improve photocatalytic performance of g-C3N4 through balancing the interstitial and substitutional chlorine doping

Cl doped g-C3N4 with controllable doping site is synthesised for the first time via an agitation-assisted solvothermal method. It is found that both the molecular and electronic structure of the prepared g-C3N4 correlates strongly with the atomic ratio of interstitial to substitutional Cl dopants (Cl-int/Cl-sub), which is determined by the agitation rate during the solvothermal synthesis. Due to the different effects of Cl-int and Cl-sub on the electronic/ molecular structure of g-C3N4, the photocatalytic activity of g-C3N4 can only be optimised by balancing the concentration of Cl-int and Cl-sub dopants. The optimal synthesis condition for Cl-doped g-C3N4 is associated with a moderate agitation rate of 60 rpm (60-C3N4). Under 60 rpm agitation during the synthesis, the 60-C3N4 exhibits remarkably larger specific surface area, stronger photo-oxidation capability, reduced bandgap and suppressed electron-hole recombination comparing with the control group g-C3N4 synthesised via conventional thermal polycondensation method. An outstanding photocatalytic RhB degradation performance is therefore observed for 60-C3N4 with similar to 35-fold higher pseudo-first reaction rate constant than the bulk g-C3N4 control group sample.