Amorphous nickel pyrophosphate modified graphitic carbon nitride: an efficient photocatalyst for hydrogen generation from water splitting

A noble-metal-free amorphous Ni2P2O7 modified g-C3N4 nanocomposite (a-Ni2P2O7/g-C3N4) has been successfully prepared by a facile calcined process. The experimental results suggest that a-Ni2P2O7/g-C3N4 displays the enhanced visible light absorption and improved charge separation relative to pristine g-C3N4, and shows smaller particle sizes and more negative conduction band edge potential than that of the crystalline Ni2P2O7 modified g-C3N4 nanocomposite (c-Ni2P2O7/g-C3N4), resulting in large amount of active sites and enhanced reduction capacity. The resultant a-Ni2P2O7/g-C3N4 is evaluated as an excellent catalyst for photocatalytic hydrogen (H-2) generation under visible light irradiation, whose H-2 generation rate is almost 5 and 37 times higher than that of c-Ni2P2O7/g-C3N4 and pristine g-C3N4, respectively, even better than that of Pt/g-C3N4. The improved activity of a-Ni2P2O7/g-C3N4 is mainly ascribed to the good visible light utilization, efficient electron-hole pairs' separation and transfer, small particle sizes and high reduction ability of electron.