金/钯哑铃状纳米晶的制备及其催化对硝基苯酚还原研究

doi:10.15541/jim20170146

摘要/Abstract

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。

关键词: 哑铃状结构, 晶种-溶液生长法, 对硝基苯酚

Abstract:

Au nanorods (Au NRs) with good monodispersity and uniform aspect ratio were prepared via seed-meditated method. Au/Pd nano-dumbbells (Au/Pd NDs) were synthesized by using H₂PdCl₄ as precursor, hexadecyl trimethyl ammonium chloride (CTAC) as soft template, Ag⁺as structure-directing agent and ascorbic acid as reduction agent to modify Au NRs. Structure and morphology of the samples were characterized by transmission electron 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 demonstrated 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 dispersibility 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.

Key words: nano-dumbbells, seed-meditated method, p-nitrophenol

中图分类号:

TQ174

殷月月, 杨勇, 张良柱, 李永生, 马云峰, 杨莉莉, 黄政仁. 金/钯哑铃状纳米晶的制备及其催化对硝基苯酚还原研究[J]. 无机材料学报, 2018, 33(1): 19-26.

YIN Yue-Yue, YANG Yong, ZHANG Liang-Zhu, LI Yong-Sheng, MA Yun-Feng, YANG Li-Li, HUANG Zheng-Ren. Facile Synthesis of Au/Pd Nano-dumbells for Catalytic Reduction of p-Nitrophenol[J]. Journal of Inorganic Materials, 2018, 33(1): 19-26.

图/表 11

图1 金纳米棒的紫外-可见-近红外吸收光谱图

Fig. 1 UV-Vis-NIR spectrum of gold NRs

图2 金纳米棒的低倍和高倍透射电镜照片(a)及其尺寸(宽度、长度)分布统计图(b-c)

Fig. 2 Low-resolution TEM and high-resolution TEM images (a) of pure Au NRs and corresponding size distributions (length, width) of Au NRs (b-c)

图3 四种对比样Au/Pd哑铃状结构的透射电镜照片(AA : Pd= 0.1 (a), AA : Pd=0.25 (b), AA : Pd= 0.5 (c), AA : Pd = 1 (d))

Fig. 3 TEM images of different Au/Pd NDs AA : Pd=0.1 (a), AA : Pd=0.25 (b), AA : Pd= 0.5 (c) and AA : Pd=1 (d)

图4 四种对比样Au/Pd哑铃结构紫外-可见-近红外光谱图

Fig. 4 UV-Vis-NIR absorption spectra of different Au/Pd NDs

图5 Au/Pd哑铃状结构的EDS分析结果

Fig. 5 EDS analysis of Au/Pd NDs

图6 Au/Pd哑铃状结构(AA : Pd=0.5)的高倍透射电镜照片

Fig. 6 HRTEM images of Au/Pd NDs (AA : Pd=0.5)

图7 Au/Pd哑铃状结构催化对硝基苯酚还原的原理示意图

Fig. 7 Schematic diagram of Au/Pd NDs for effective catalytic reduction of p-nitrophenol

图8 AuNRs催化对硝基苯酚还原的紫外可见光谱图(a), 四种Au/Pd哑铃状结构催化对硝基苯酚还原的紫外可见光谱图(b-e), AuNRs以及四种Au/Pd哑铃状结构催化对硝基苯酚还原的速率常数(f)

Fig. 8 UV-Vis absorption spectra of AuNRs (a), different Au/Pd NDs (b-e) for effective catalytic reduction of p-nitrophenol, ln(C/C0) against time for the determination of rate constant in presence of AuNRs and Au/Pd NDs for effective catalytic reduction of p-nitrophenol (f)

表1 AuNRs和Au/Pd哑铃状结构催化还原对硝基苯酚的催化活性对比

Table 1 Catalytic activity comaprison of AuNRs and Au/Pd NDs for the reduction of 4-nitrophenol

Nature of the catalyts	Size of palladium nanoparticles/nm	Rate constant/min^-1
AuNRs	0	0.02
AA : Pd=0.10	11.4	0.16
AA : Pd=0.25	15.6	0.22
AA : Pd=0.50	20.7	0.38
AA : Pd=1.00	33.6	0.18

图9 Au/Pd哑铃状结构不同催化剂用量催化对硝基苯酚还原紫外-可见光谱图(a-c)和速率常数(d)

Fig. 9 UV-Vis absorption spectra of Au/Pd NDs for effective catalytic reduction of p-nitrophenol (a-c) and ln (Ct/C0) against time for the determination of rate constant (d)

表2 钯基纳米颗粒催化还原对硝基苯酚的催化活性对比

Table 2 Catalytic activity comaprison of Pd based nanoparticle for the reduction of 4-nitrophenol

Nature of the catalyst	Rate constant/min^-1	Concentration of catalyst/(mg·mL^-1)	Concentration of 4-NP/(mmol·L^-1)	References
Pd supported on TiO₂ microspheres	0.190	0.070	10.00	[30]
Pd on partially reduced graphene oxide	14.400	0.100	10.00	[31]
Pd immobilized on multiwalled carbon nanotube	0.014	0.250	0.06	[32]
Pd stabilized by glycodendrimers in water	0.240	0.240	0.25	[33]
Pd-tipped AuNRs	0.130	0.002	0.40	[17]
Au/Pd NDs	0.440	0.004	10.00	Current study

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