Superhydrophilic 2D carbon nitrides prepared by direct chemical vapor deposition

Abstract

Surface wetting greatly impacts the performances of many photocatalysts in a water/humid-involved medium. Carbon nitrides and its isotopes, as emerging metal-free low-cost photocatalysts for water splitting, usually require strong chemical or irradiation treatments to obtain highly hydrophilic surfaces, which can undermine their photocatalytic performances. Herein, an alternative method for the direct synthesis of superhydrophilic carbon nitride thin films (CNx, x approximate to 0.86-1.04) and graphitic carbon nitride powder (g-C3N4) by using chemical vapor deposition is proposed. Less than 5 degrees contact angle with water is accessible on both the surface of the as-grown CNx thin films and the membranes made from the g-C3N4 powder. It is found that the remarkable wetting property can be attributed to the spontaneous hydrophilic functionalization group (e.g., -OH, -NOx, = O) supplied by a constant multielemental air flow. The abundant CN triple bonds also promote needle-shaped nanostructures on the 2D surfaces, which enhances their chemical wettability. Finally, the tremendous potential of this novel technique for direct synthesis of superhydrophilic carbon nitride in photocatalysis applications is demonstrated.