Preparation of 2D hydroxyl-rich carbon nitride nanosheets for photocatalytic reduction of CO2

Hydroxyl-rich g-C3N4 nanosheets were prepared by ultrasonic exfoliation of bulk g-C3N4 in water. The samples were characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, atomic force microscopy, UV-vis absorption spectroscopy, photoluminescence spectroscopy, time-resolved fluorescence decay spectroscopy, Fourier-transform infrared spectroscopy, X-ray photoelectron spectroscopy and photocurrent response. The results indicated that the bulk g-C3N4 was exfoliated to five or six layers. The specific surface area increased from 8.66 m(2) g(-1) for the bulk g-C3N4 to 26.48 m(2) g(-1) for the nanosheets. More importantly, the amount of hydroxyl group on the g-C3N4 surface increased greatly upon ultrasonic treatment in water. Meanwhile, the separation rate of charge carriers was improved greatly and the conduction band potential shifts to a more negative value. All these can explain the enhanced activity of g-C3N4 nanosheets for visible-light photocatalytic reduction of CO2.