金/钯哑铃状纳米晶的制备及其催化对硝基苯酚还原研究

摘要

采用晶种-溶液生长法制备了单分散性良好、长径比均一的Au纳米棒,利用H2PdCl4作为前驱体,CTAC作为软模版,抗坏血酸作为还原剂对Au纳米棒进行改性合成了金/钯哑铃状结构纳米晶(Au/Pd NDs).采用透射电子显微镜(TEM)、X射线能谱仪(EDS)和紫外-可见分光光度计(UV-Vis-NIR)对样品的结构和形貌进行表征,探讨了铃铛状结构形成的机理,并研究了其对硼氢化钠还原对硝基苯酚反应的催化性能.结果表明:大量的多晶钯颗粒定向选择生长在金纳米棒(AuNRs)两端,形成哑铃状结构;通过调控还原剂与前驱体的比例,铃铛尺寸连续可调.当钯的分散性好且总的催化活性位点多时,金/钯哑铃状结构纳米晶催化对硝基苯酚还原的效率高.钯颗粒尺寸为20.7 nm的Au/Pd NDs(0.04 mg/mL)催化对硝基苯酚还原的反应速率常数可达0.44 min-1,证明其是一种非常有效的催化剂.%Au nanorods (Au NRs) with good monodispersity and uniform aspect ratio were preparedvia seed-meditated method. Au/Pd nano-dumbbells (Au/Pd NDs) were synthesized by using H2PdCl4 as precursor, hexa-decyl trimethyl ammonium chloride (CTAC) as soft template, Ag+as structure-directing agent and ascorbic acid as re-duction agent to modify Au NRs. Structure and morphology of the samples were characterized by transmission elec-tron microscope (TEM), energy dispersive spectrometer (EDS) and ultraviolet-visible-near infrared spectrophotometry (UV-Vis-NIR). The formation mechanism of Au/Pd NDs were discussed. The results of Au/Pd NDs samples demon-strated that lots of poly-crystalline Pd particles were deposited onto two ends of Au nanorods selectively to form dumbbell-like structure. The dumbbell size can be continuously tuned by adjusting the molar ratio of AA and H2PdCl4. The experiments of reduction of p-nitrophenol by NaBH4 to p-aminophenol indicate that the sample with good dis-persibility and large number of total catalytic active sites of Pd nanoparticles has high catalytic performance. Adding 0.04 mg/mL Au/Pd NDs with suitable Pd particles size (20.7 nm) show excellent catalytic activity (rate constant 0.44 min-1), indicating it is useful for reducing p-nitrophenol.