高(111)晶面暴露的Pd纳米颗粒的制备与表征及其加氢性能

通过液相氢气还原法，在不同温度下制备出了不同（111）晶面占比的Pd单晶纳米颗粒，用活性炭吸附制备成Pd/C纳米催化剂。通过透射电子显微镜（TEM）、傅里叶变换（FFT）、X射线衍射（XRD）表征证实了低温下制备的Pd纳米颗粒具有较高的（111）晶面占比。氢氧脉冲滴定（H₂-O₂）和H₂-程序升温脱附（H₂-TPD）结果显示，上述催化剂表面吸附氢气量与其Pd（111）晶面占比呈线性关系。此外，该系列Pd/C催化剂具有相似的粒径4.3 nm以及较窄的尺寸分布，相近的孔隙参数和Pd负载量，从而可对比（111）晶面比例差异对其加氢性能的影响。3个探针反应（苯乙烯、环己烯和对硝基甲苯的加氢反应）的实验结果表明，相比于低（111）晶面暴露比例的Pd/C催化剂，含有高（111）晶面暴露比例的Pd/C催化剂显示出更高的加氢活性，且Pd（111）晶面比例与氢气消耗速率呈一定的线性关系，这归因于H₂优先吸附于Pd（111）晶面促进了活性氢原子的形成。基于以上分析，高（111）晶面暴露的Pd基催化剂有利于加氢性能的提高。

Synthesis and Characterization of Palladium Nanoparticles with High Proportion of Exposed (111) Facet for Hydrogenation Performance

Pd nanoparticles with different (111) facet proportions were prepared at by a liquid phase hydrogen reduction method, then preparing corresponding Pd/C catalysts. The results of transmission electron microscopy (TEM), fast Fourie transition (FFT), and X-ray diffraction (XRD) revealed that the proportion of the (111) facets on the Pd surface was higher at lower temperatures. Hydrogen oxygen pulse titration (H₂-O₂) and H₂-temperature programmed desorption (H₂-TPD) showed that the hydrogen adsorption volume of Pd/C catalysts was correlated linearly with the Pd(111) facet proportions. All Pd/C catalysts had an average particle size of 4.3 nm with narrow particle size distribution, which could eliminated the effect of particle size. The similar pore parameters and Pd loading of all catalysts allowed the reasonable comparison for Pd(111) facet proportions influenced the hydrogenation performance in three typical reactions. Moreover, linear correlations were found between the H₂ consumption rate with Pd (111) facet proportions in each of styrene, cyclohexene, and p-nitrotoluene hydrogenation. The good catalytic performance of high Pd(111) facet proportion catalyst for hydrogenations could be attributed to the H₂ molecule prior to absorbed the Pd(111) facet promoting the formation of dissociated hydrogen atoms. These results above indicated that Pd-based catalysts with high (111) facet proportion facilitated hydrogenation performance.