Template-free synthesis of tetragonal graphitic carbon nitride microtubes doped by sodium chloride for enhanced photocatalytic H2 performance under visible light irradiation

Element doping and nanostructure forming remain the effective means to improve the visible-light driven photocatalytic performance for graphitic carbon nitride (CN). Herein, Na/Cl doped g-C3N4 with tetragonal microtube structure is successfully prepared by a hydrothermal method using melamine and sodium chloride as precursors. Nanostructure formation increases the specific surface area of the 3wt% NaCl-CN photocatalyst to 76.8 m(2)/g from 25.8 m(2)/g of CN. The Na/Cl doping reduces the band gap and effectively improves separation and transport of photoinduced carriers. The photocatalytic hydrogen evolution rate of 3wt% NaCl-CN reaches 4.95 mu mol/h, which is about 4.3 times as high as that of CN. Not only does the more specific surface area increase, and the visible light harvesting increase, but also the photoinduced carriers become more effectively separated and transported, facilitating the photocatalytic performance by the synergistic effect of element doping and nanostructure forming.