New Chemistry Unit, Jawaharlal Nehru Centre for Advanced Scientific Research , Jakkur, Bangalore 560064, India.
Elettra Sincrotrone Trieste SCpA , SS14 Km 163.5, Trieste, Basovizza 34149, Italy.
ACS Appl Mater Interfaces. 2017 Feb 1;9(4):3602-3615. doi: 10.1021/acsami.6b12253. Epub 2017 Jan 23.
Synthesis of ordered compounds with nano size is of particular interest for tuning the surface properties with enhanced activity and selectivity toward various important industrial catalytic processes. In this work, we synthesized ordered PdCu nanoparticles as highly efficient catalyst for the solvent-free aerobic oxidation of benzylamine. The PdCu catalysts with different chemical compositions (x = 0, 0.25, 0.4, 0.5, 0.6, 0.75, 1) were prepared by polyol method using NaBH as a reducing agent and were well-characterized by X-ray diffraction (XRD), inductively coupled plasma optical emission spectroscopy, X-ray photoelectron spectroscopy, transmission electron microscopy (TEM) energy-dispersive analysis of X-rays, and X-ray absorption fine structure. The effect of different metal concentrations of Pd and Cu on the formation of PdCu nanoparticles was investigated. The XRD and TEM confirmed the formation of ordered PdCu intermetallic phase with body-centered cubic (BCC) structure for the synthetic composition of Pd/Cu = 1:1. For compositions x = 0, 0.25, 0.75, and 1, PdCu alloy with face-centered cubic (FCC) structure was observed, whereas mixed phase of BCC and FCC was observed for x = 0.4 and 0.6. The use of strong reducing agent (NaBH) was essential to synthesize PdCu ordered phase compared to weak reducing agents such as oleylamine and ascorbic acid. The PdCu nanocatalyst with ordered structure (BCC) showed excellent catalytic activity compared to PdCu alloy nanoparticles with FCC structure. The atomic ordering in the PdCu intermetallic was the driving force for the enhancement in the catalytic activity with high benzylamine conversion of 94.0% and dibenzylimine selectivity of 92.2% compared to its monometallic and alloy counterparts. Moreover, ordered PdCu alloy showed good recyclability and activity toward the oxidation of different amines.
合成具有纳米尺寸的有序化合物对于调整表面性能以提高对各种重要工业催化过程的活性和选择性具有特别的意义。在这项工作中，我们合成了有序的 PdCu 纳米颗粒作为高效催化剂，用于无溶剂条件下苄胺的有氧氧化。通过多元醇法使用 NaBH4 作为还原剂，制备了具有不同化学组成（x = 0、0.25、0.4、0.5、0.6、0.75、1）的 PdCu 催化剂，并通过 X 射线衍射（XRD）、电感耦合等离子体发射光谱、X 射线光电子能谱、透射电子显微镜（TEM）、X 射线吸收精细结构进行了很好的表征。研究了不同 Pd 和 Cu 金属浓度对 PdCu 纳米颗粒形成的影响。XRD 和 TEM 证实了有序 PdCu 金属间相的形成，具有体心立方（BCC）结构，合成的 Pd/Cu 比为 1:1。对于 x = 0、0.25、0.75 和 1，观察到 PdCu 合金具有面心立方（FCC）结构，而对于 x = 0.4 和 0.6，观察到 BCC 和 FCC 的混合相。与弱还原剂如油胺和抗坏血酸相比，使用强还原剂（NaBH4）对于合成 PdCu 有序相是必不可少的。与 FCC 结构的 PdCu 合金纳米催化剂相比，具有有序结构（BCC）的 PdCu 纳米催化剂表现出优异的催化活性。PdCu 金属间化合物的原子有序性是提高催化活性的驱动力，与单金属和合金相比，具有 94.0%的高苄胺转化率和 92.2%的二苄基亚胺选择性。此外，有序 PdCu 合金对不同胺的氧化表现出良好的可回收性和活性。
