Photo- and electro-catalysis evolution of superior thin g-C3N4 nanosheets with their microstructure and Ni Fe oxide composite

Graphitic carbon nitride (g-C3N4) is normally used in photocatalysis under visible light, to realize its' enhanced electrocatalytic hydrogen evolution reaction is still a challenge. In this paper, superior thin g-C3N4 nanosheets with different composition and crystallinity are prepared via theromal polarization process to test their photo- and electro-chemical activities. Interestingly, a crystalline/amorphous g-C3N4 nanosheet homojunctions are successfully prepared via one-step thermal polymerization by adjusting preparation parameters. Crystalline and amorphous phases are homogeneously distributed in thin g-C3N4 nanosheets. Compared with crystalline and amorphous g-C3N4 nanosheets, the homojunction prepared using optimized C/N ratio and crystalline/amorphous phase distribution reveals the quick photodegradation of dyes. NiFe oxides are deposited on g-C3N4 by a further thermal polymerization process. After loading metal oxides, the photo- and electro-catalytic performance of crystalline/amorphous homojunctions is greatly enhanced. Especially, the co-loading of Fe2O3 and NiO drastically enhances the electrochemical performance of g-C3N4 nanosheet homojunctions. Using optimized loading amount, the overpotentials of amorphous g-C3N4 nanosheets, g-C3N4 amorphous/crystalline nanosheet homojunctions, and crystalline g-C3N4 nanosheets are 756, 691 and 672 mV for electrochemical hydrogen evolution reaction with Tafel slope of 101, 79 and 74 mV/dec, respectively.