Facile synthesis and enhanced photocatalytic H2-evolution performance of NiS2-modified g-C3N4 photocatalysts

NiS2 is a promising cocatalyst to improve the photocatalytic performance of g-C3N4 for the production of H-2. However, the synthesis of the NiS2 cocatalyst usually requires harsh conditions, which risks destroying the microstructures of the g-C3N4 photocatalysts. In this study, a facile and low -temperature (80 degrees C) impregnation method was developed to prepare NiS2/g-C3N4 photocatalysts. First, the g-C3N4 powders were processed by the hydrothermal method in order to introduce oxygen -containing functional groups (such as-OH and-CONH-) to the surface of g-C3N4. Then, the Ni2+ ions could be adsorbed near the g-C3N4 via strong electrostatic interaction between g-C3N4 and Ni2+ ions upon the addition of Ni(NO3)(2) solution. Finally, NiS2 nanoparticles were formed on the surface of g-C3N4 upon the addition of TAA. It was found that the NiS2 nanoparticles were solidly and homogeneously grafted on the surface of g-C3N4, resulting in greatly improved photocatalytic H-2 production. When the amount of NiS2 was 3 wt%, the resultant NiS2/g-C3N4 photocatalyst showed the highest H-2 evolution rate (116.343 mu mol h(-1) g(-1)), which is significantly higher than that of the pure g-C3N4 (3 umol h(-1) g(-1)). Moreover, the results of a recycling test for the NiS2/g-C3N4(3 wt%) sample showed that this sample could maintain a stable and effective photocatalytic H-2 -evolution performance under visible-light irradiation. Based on the above results, a possible mechanism of the improved photocatalytic performance was proposed for the presented NiS2/g-C3N4 photocatalysts, in which the photogenerated electrons of g-C3N4 can be rapidly transferred to the NiS2 nanoparticles via the close and continuous contact between them; then, the photogenerated electrons rapidly react with H2O adsorbed on the surface of NiS2, which has a surficial metallic character and high catalytic activity, to produce H-2. Considering the mild and facile synthesis method, the presented low-cost and highly efficient NiS2-modified g-C3N4 photocatalysts would have great potential for practical use in photocatalytic Hz production. (C) 2016, Dalian Institute of Chemical Physics, Chinese Academy of Sciences. Published by Elsevier B.V. All rights reserved.