Structure defects promoted exciton dissociation and carrier separation for enhancing photocatalytic hydrogen evolution

Structure defect poor and rich graphitic carbon nitrides (g-C3N4) were successfully prepared to disclose the relationships between structure defects and the exciton/carrier behaviors. The partial loss of the heptazine units in the matrix was the origin of the intrinsic structure defects in the g-C3N4, evidenced by the X-ray photoelectron spectroscopic analysis. Both the fluorescence and ultrafast transient absorption analyses demonstrated that the presence of the intrinsic structure defects within g-C3N4 promoted the dissociation of excitons and the separation of photogenerated carriers, reflected by the accelerated relaxation of the excited electrons from conduction band to the trap states and the prolonged relaxation of trapped electrons to the valence band. Thus, the structure defect rich g-C3N4 performed better in photocatalytic hydrogen production than structure defect poor g-C3N4. This study not only disclosed the influences of the intrinsic structure defects on exciton/carrier behaviors, but also provide an alternative perspective to modify the semiconductors for photocatalytic applications.