物理化学学报

最新录用 上一篇    下一篇

Pt@Au/Al2O3核壳纳米粒子的制备和表征及其在催化氧化甲苯中的应用

张超, 李思汉, 吴辰亮, 李小青, 严新焕   

  1. 浙江工业大学绿色化学合成技术国家重点实验室培育基地, 杭州 310014
  • 收稿日期:2019-07-19 修回日期:2019-08-27 录用日期:2019-09-09 发布日期:2019-09-11
  • 通讯作者: 严新焕 E-mail:xhyan@zjut.edu.cn
  • 基金资助:
    国家重点研发计划(2017YFC0210900)与浙江省科技计划项目(2016C31104)资助

Preparation and Characterization of Pt@Au/Al2O3 Core-Shell Nanoparticles for Toluene Oxidation Reaction

Chao Zhang, Sihan Li, Chenliang Wu, Xiaoqing Li, Xinhuan Yan   

  1. State Key Laboratory Breeding Base of Green Chemistry-Synthesis Technology, Zhejiang University of Technology, Hangzhou 310014, P. R. China
  • Received:2019-07-19 Revised:2019-08-27 Accepted:2019-09-09 Published:2019-09-11
  • Supported by:
    The project was supported by the National Key R&D Program (2017YFC0210900) and Zhejiang Science and Technology Plan Project, China (2016C31104).

摘要: 采用种子生长法,在不存在保护剂和结构导向剂的情况下,成功制备Pt@Au核壳结构纳米颗粒,即在Pt纳米颗粒表面,AuCl4-被H2还原成Au(0),并沉积在Pt核纳米颗粒上。通过透射电子显微镜(TEM),能量色散X射线光谱(EDS),高分辨率TEM(HRTEM),傅里叶变换(FFT)和X射线粉末衍射(XRD),X射线光电子能谱(XPS),红外光谱(IR)和H2-程序升温还原(H2-TPR)等表征证实了核壳结构。所制得的Pt@Aux/Al2O3催化剂在常压下由固定床反应器测定其在甲苯氧化中的活性。相比于单金属催化剂Pt/Al2O3与Au/Al2O3,Pt@Aux/Al2O3核壳催化剂显示出更高的催化活性,且Pt1@Au1/Al2O3对于甲苯氧化具有最好的催化活性,这归因于Au和Pt之间的电子交换促进了Au上活性氧的形成。Pt@Aux/Al2O3对甲苯氧化良好的催化性能和高选择性与其较高的吸附氧物质浓度,较好的低温还原性和强相互作用有关。

关键词: 催化剂, 协同作用, 纳米材料, 核壳结构, VOCs

Abstract: Customizing core-shell nanostructures is considered to be an efficient approach to improve the catalytic activity of metal nanoparticles. Various physiochemical and green methods have been developed for the synthesis of core-shell structures. In this study, a novel liquid-phase hydrogen reduction method was employed to form core-shell Pt@Au nanoparticles with intimate contact between the Pt and Au particles, without the use of any protective or structure-directing agents. The Pt@Au core-shell nanoparticles were prepared by depositing Au metal onto the Pt core; AuCl4- was reduced to Au(0) by H2 in the presence of Pt nanoparticles. The obtained Pt@Au core-shell structured nanoparticles were characterized by transmission electron microscopy (TEM), energy-dispersive X-ray spectroscopy (EDX), high-resolution TEM, fast Fourier transform, powder X-ray diffraction (PXRD), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FTIR), and H2-temperature programmed reduction (H2-TPR) analyses. The EDX mapping results for the nanoparticles, as obtained from their scanning transmission electron microscopy images in the high-angle annular dark-field mode, revealed a Pt core with Au particles grown on its surface. Fourier transform measurements were carried out on the high-resolution structure to characterize the Pt@Au nanoparticles. The lattice plane at the center of the nanoparticles corresponded to Pt, while the edge of the particles corresponded to Au. With an increase in the Au content, the intensity of the peak corresponding to Pt in the FTIR spectrum decreased slowly, indicating that the Pt nanoparticles were surrounded by Au nanoparticles, and thus confirming the core-shell structure of the nanoparticles. The XRD results showed that the peak corresponding to Pt shifted gradually toward the Au peak with an increase in the Au content, indicating that the Au particles grew on the Pt seeds; this trend was consistent with the FTIR results. Hence, it can be stated that the Pt@Au core-shell structure was successfully prepared using the liquid-phase hydrogen reduction method. The catalytic activity of the nanoparticles for the oxidation of toluene was evaluated using a fixed-bed reactor under atmospheric pressure. The XPS and H2-TPR results showed that the Pt1@Au1/Al2O3 catalyst had the best toluene oxidation activity owing to its lowest reduction temperature, lowest Au 4d & 4f and Pt 4d & 4f binding energies, and highest Au0/Auδ+ and Pt0/Pt2+ proportions. The Pt1@Au2Al2O3 catalyst showed high stability under dry and humid conditions. The good catalytic performance and high selectivity of Pt@Au/Al2O3 for toluene oxidation could be attributed to the high concentration of adsorbed oxygen species, good low-temperature reducibility, and strong interaction.

Key words: Catalyst, Synergy, Nanomaterials, Core-shell structure, VOCs

MSC2000: 

  • O643