Influence of the Capping Agent PVP of the Outer Layer of Pd Nanocubes Surface on the Catalytic Hydrogenation of Unsaturated C−C Bonds

The excess of capping agents used during the synthesis of nanoparticles is usually removed by solvent washing. The influence of the amount of polyvinylpyrrolidone (PVP) capping agent in the catalytic activity of palladium nanocubes was evaluated, after different numbers of washing cycles in the purification step performed after the syntheses of the nanoparticles. The effect of PVP amount on the hydrogenation of unsaturated carbon-carbon bonds was evaluated in terms of kinetic analysis and diffusion experiments. Five different catalysts were prepared utilizing the washing off procedure. All catalysts were characterized by transmission electron microscopy, X-ray photoelectron spectroscopy, small angle X-ray scattering spectroscopy and dynamic light scattering. The reaction presented strong influence by the amount of PVP, which was determined to be due to a balance between the amount of capping agent and the structure of the substrate.

纳米颗粒合成过程中所使用的过量封端剂，通常通过溶剂洗涤法去除。本研究在纳米颗粒合成后的纯化步骤中设置不同次数的洗涤循环，以此评估聚乙烯吡咯烷酮（polyvinylpyrrolidone, PVP）封端剂的用量对钯纳米立方体催化活性的影响。针对不饱和碳-碳键的加氢反应，通过动力学分析与扩散实验，探究了PVP用量对该反应的作用效应。本研究采用洗涤工艺制备了五种不同的催化剂，并通过透射电子显微镜、X射线光电子能谱、小角X射线散射光谱及动态光散射对所有催化剂进行了表征。实验结果显示，该加氢反应受PVP用量的显著影响，经分析确定该影响源于封端剂用量与底物结构之间的平衡关系。