Carbon-vacancy modified graphitic carbon nitride: Enhanced CO ₂ photocatalytic reduction performance and mechanism probing

The obstacles to achieving high CO ₂ photoreduction performance on graphitic carbon nitride (GCN) are commonly ascribed to its weak CO ₂ activation capability and low charge carrier concentration. To overcome these obstacles, here we report a new class of GCN with C vacancies intentionally introduced by heat treatment in an NH ₃ atmosphere. GCN with enriched C vacancies exhibits more than two times higher CO ₂ -to-CO conversion rate than pristine GCN. Our detailed characterization reveals that the improved CO ₂ reduction performance of this carbon-vacancy modified GCN is attributed to the enhanced CO ₂ adsorption/activation, upshifted conduction band and elevated charge carrier concentration and lifetime. Moreover, we discover that the introduction of C vacancies into GCN could attenuate the exciton-effect and favor the charge carrier generation. These results not only provide insights on regulating the structure of GCN to promote its CO ₂ photoreduction performance, but also pave the way to tune the exciton effect and charge carrier concentration in GCN to facilitate photoinduced electron-hole separation and charge-carrier-involved photocatalytic reaction.