Alkali-assisted fabrication of holey carbon nitride nanosheet with tunable conjugated system for efficient visible-light-driven water splitting

Graphitic carbon nitride (CN) nanosheets have aroused a great deal of interest due to their capability to utilize visible light to split water into its constituent molecules of hydrogen and oxygen (H-2 and O-2). However, the photocatalytic capacity of conventional bulk g-C3N4, with its large pi-pi conjugated electronic system, is still constrained by the pi-pi stacking interaction and small number of active sites. Hence, an uncomplicated post processing method to construct a different pi-pi conjugated electronic system of holey CN nanosheets using alkali etching of bulk CN (CN (B)) at 300 degrees C for 1 h has been developed. Among such compounds, the optimal alkali treatment bulk CN (CN 3(2)) exhibits a suitable conjugated system and copious in-plane holes, and it retains the ability to absorb sunlight during alkali depolymerization. Compared to CN (B), the resultant CN 3(2) has a distensible bandgap of 2.66 eV associated with a much larger specific surface area of 265.2 m(2) g(-1). However, excessive alkali treatment significantly decrease the visible light absorbance and the photocatalytic properties of the CN nanosheet, which demonstrated that a suitable pi-pi conjugated electronic system is very important in allowing the process to proceed. As such, the photocatalytic H-2 and O-2 production rate of CN 3(2) was nearly 24.6 times that of CN (B) with the addition of carbon quantum dots (CQDs) and Pt.