Z-型CdZnS/Ag/NCN异质结光催化剂的制备及可见光析氢性能研究

Constructing Z-type CdZnS/Ag/NCN heterojunction for visible-light-driven photocatalytic hydrogen generation

摘要:

纯有机半导体所固有的较高激子结合能和低电荷分离效率是限制氮化碳光催化析氢性能和应用的关键问题．通过对以双氰胺为原料生成的氮化碳在氨气气氛下的二次气相反应，在氮化碳末端成功引入胺基基团，增强了氮化碳的水相分散能力和配位能力．然后通过硼氢化钠原位还原法在这种氮掺杂氮化碳表面负载银，再通过超声搅拌使将所得产物与不同Cd/Zn摩尔比的硫锌镉（CdZnS-X）自由组合，从而构建了以单质银作为载流子转移媒介的Z型CdZnS/Ag/NCN异质结．实验结果表明：以体积百分数20%的三乙醇胺作为空穴牺牲剂，当硫锌镉中r（Cd）∶r（Zn）∶r（S）=2∶8∶10时，Z型CdZnS/Ag/NCN异质结复合物的可见光（λ>420 nm）析氢效率可达1279.45 μmol/（h·g），是氮掺杂氮化碳的4.4倍及硫锌镉的5.8倍．光谱和电化学实验结果表明，Z型CdZnS/Ag/NCN异质结复合材料性能的显著提升，主要是由于Z型异质结促进了单一组分的电荷分离，增大了固/液接触面和反应活性位点．

Abstract:

The high exciton binding energy and low charge separation efficiency of pure organic semiconductors are considered to be the key problems limiting the performance and application of carbon nitride for photocatalytic hydrogen evolution. In this paper， the secondary gas-phase reaction of carbon nitride was carried out in ammonia atmosphere. The amino group was successfully introduced into the carbon nitride， which enhanced the dispersing and coordination ability of carbon nitride in the aqueous phase. Silver was loaded on the surface of the nitrogen-doped carbon nitride by sodium borohydride in situ reduction method. The Z-type heterojunction with silver as carrier transfer medium was constructed under assistance of sonication and stirring， as well as self-assembling of the product and CdZnS-X with different Cd/Zn molar ratio. When the molar ratio of Cd∶Zn∶S is 2∶8∶10 and 20 vol% triethanolamine was used as hole sacrificing agent， the hydrogen evolution efficiency of 1279.45 μmol/（h·g） （λ>420 nm） was obtained for heterojunction. This value is 4.4 times higher than that of nitrogen-doped carbon nitride and 5.8 times higher than that of sulfur zinc cadmium. The results of spectroscopy and electrochemistry show that the significant improvement in the properties of the composites is mainly due to the enhancement of the charge separation of single component， and the increased solid/liquid interface and the concentration of active sites.