One‐Step Realization of Crystallization and Cyano‐Group Generation for g‐C3N4 Photocatalysts with Improved H2 Production

In contrast to conventional disordered g‐C 3 N 4 , the ordered arrangement of s‐triazine units and cyano‐group is important for its improved photocatalytic H 2 evolution activity. However, the usual synthetic methods include complex, multiple‐step operations or containing the use of toxic materials. Herein, the ordered crystallization and cyano‐group generation are simultaneously realized for the g‐C 3 N 4 photocatalyst (namely, cyano‐group‐modified crystalline g‐C 3 N 4 ) by a facile and green one‐step Na 2 CO 3 ‐assisted synthesis approach. It is found that Na 2 CO 3 first effectively promotes the denitrification of dicyandiamide (DCDA) and accelerates its polymerization to produce highly crystalline g‐C 3 N 4 . When the temperature is over 500 °C, Na 2 CO 3 facilitates the pyrolysis of partial s‐triazine units to produce cyano‐groups on the g‐C 3 N 4 surface, resulting in the final generation of cyano‐group‐modified crystalline g‐C 3 N 4 . Consequently, the resulting cyano‐group‐modified crystalline g‐C 3 N 4 presents a highly increased hydrogen production activity, about twofold higher than that of the bulk g‐C 3 N 4 . The increased hydrogen production activity is primarily because of the synergistic effect of the highly crystalline and cyano‐group functional for the resulting cyano‐group‐modified crystalline g‐C 3 N 4 . The current technology opens insights for the preparation of other crystalline photocatalysts.