Metal Ni-loaded g-C3N4 for enhanced photocatalytic H2 evolution activity: the change in surface band bending.

A series of Ni@g-C3N4 composites were synthesized by a simple solvent thermal method using melamine and acetylacetone nickel as precursors. The results of X-ray diffraction, transmission electron microscopy and high resolution transmission electron microscopy indicate that Ni was successfully loaded on g-C3N4. And the Ni loaded greatly enhances the photocatalytic H2 evolution activity of g-C3N4 compared to the pure g-C3N4. In order to study the role of Ni, the surface photovoltage, the surface photocurrent and photoluminescence measurements were used to investigate the photogenerated charge properties of g-C3N4. What is more, Mott-Schottky plots and work function measurements confirmed the surface band bending change of g-C3N4 contacting with Ni. Those results demonstrate that Ni coating deepens surface band bending of g-C3N4, resulting in higher separation efficiency of photogenerated charge carriers, which is contributed to the enhanced photocatalytic H2 evolution activity.