Photocatalytic Materials Based Upon Graphitic Carbon Nitride （g-C₃N₄） In The Region Of Visible Light

Hydrogen as a secondary energy source has a high-energy density of chemical fuel.Photocatalytic water splitting driven by solar energy is a promising way to produce hydrogen.This dissertation aims to improve the water-splitting performance of g-C3N4.The preparation process of different methods(calcination and hydrothermal/solvothermal method)and different precursors(urea,melamine,melamine,thiourea)was studied and characterized.The research was focused on the preparation from urea calcination,and there was no further doping treatment of graphite carbon nitride for hydrothermal/solvothermal method.Increasing the specific surface area is a useful method to improve the efficiency of the photocatalyst,as it will increase the active sites of the photocatalyst,and decrease the recombination rate of photo-generated charge carriers.This dissertation reports a simply secondary calcination process to exfoliate the two-dimensional layers of g-C3N4 without using any soft or hard templates.The resulting ultrathin g-C3N4 nanosheets have a high specific surface area up to 648 m2 g-1.The photocatalytic performance of hydrogen evolution under visible LED irradiation is as high as 2.56 mmol h-1 g-1.It was also found that the photocatalysts could still have a satisfactory photocatalytic activity after the long-time cyclic testing,which showed high stability and recycle ability.