可控合成La（OH）3纳米球光催化去除NO及其催化性能机制研究

以KOH和La(NO3)3·6H2O为前驱体,柠檬酸为保护剂,采用一步水热法合成三维La(OH)3纳米球光催化剂.通过XRD、SEM、PL和UV-vis DRS等对样品进行结构表征.结果表明,柠檬酸的加入量对La(OH)3的形貌均匀性和催化活性均有较大影响.柠檬酸和La(NO3)3·6H2O的物质的量的比为2∶1时,得到的样品为形貌均匀的纳米球,光催化活性最佳且稳定性好.这是因为三维的纳米球结构更容易促进光生载流子的分离;此外,形貌均匀无团聚,增加了催化剂表面的活性位点,使反应过程中反应物和中间产物迅速扩散,从而光催化活性最高.在光催化过程中,羟基自由基(·OH)和超氧自由基(·O-2)是最主要的氧化物种.NO可以和产生的·OH和·O-2反应生成HNO2和HNO3,从而去除NO.本文研究结果充实了La(OH)3光催化材料的合成基础理论,探讨了La(OH)3光催化活性机理,为La(OH)3应用打开了新的视野.

Controlled synthesis of La(OH)3 nanospheresphotocatalytic removal of NO and the mechanism of photocatalysis

The novel 3D structure of La(OH)₃ nanospheres have been synthesized by a hydrothermal method using KOH, La(NO₃)₃·6H₂O as precursors and citric acid as a protective agent.The as-prepared samples were systematically characterized by XRD, SEM, PL, and UV-vis DRS. The results indicated that the content of citric acid have great influence on the morphology uniformity and photocatalytic activity of La(OH)₃. The highest photocatalytic performance and stability can be achieved when the molar ratio of citric acid to La(NO₃)₃·6H₂O is controlled at 2:1. The high activity of thecitricacid:La=2:1 sample can be attributed to the three dimensional nanosphere structure could facilitate the separation of photoinducedchargecarriers. Besides, the morphology of nanospheres which are uniformly dispersed and regular, it not only creates more unsaturated surface coordination sites but also promote the transfer of reactants and products instead of accumulating on the surface. As the ·OH and ·O₂^- radicals are the major reactive species, the NO could react with the photogenerated ·OH and ·O₂^- radicals generated from the photocatalytic reaction in the presence of the as-prepared photocatalyst to produce HNO₂ and HNO₃. The photocatalysis mechanism of La(OH)₃ nanospheres was also proposed. This work enriched the synthesis theory of La(OH)₃ photocatalytic materials and opened the new field vision for La(OH)₃ applications.