Constructing confined surface carbon defects in ultrathin graphitic carbon nitride for photocatalytic free radical manipulation

The porous ultrathin graphitic carbon nitride (g-C3N4) with confined surface carbon defects was obtained via the twice thermal treatment of bulk g-C3N4. The as-prepared porous ultrathin g-C3N4 sample displayed the average thickness of about 0.9 nm. The porous ultrathin g-C3N4 with confined surface carbon defects was designed to bidirectional acceleration of carrier separation for both the bulk and the surface. Multiple characterizations have been employed to determine the structure, morphology, surface feature, defect, and electronic structure of the obtained samples. The photocatalytic activity of the obtained porous ultrathin g-C3N4 materials was evaluated for the degradation of rhodamine B under the visible light irradiation. The structure-activity relationship of the porous ultrathin g-C3N4 materials was studied in details. The free radicals during the photocatalysis process was determined and analyzed by electron spin resonance and X-ray photoelectron spectroscopy valence band spectra technique, in which the main free radicals would be changed from superoxide radical for bulk g-C3N4 to both superoxide radical and hydroxyl radical for porous ultrathin g-C3N4. This ideal material model disclosing atomic-level insights into the role of porous ultrathin structure with confined carbon defects in the enhanced photocatalytic activity.