Wei Qiuli, Liu Tongjun, Wang Yuanyuan, Dai Liyi
College of Chemistry and Molecular Engineering, East China Normal University 500 Dongchuan Road Shanghai 200241 China
RSC Adv. 2019 Mar 26;9(17):9620-9628. doi: 10.1039/c9ra00230h. eCollection 2019 Mar 22.
Herein, three-dimensional (3D) nitrogen-doped graphene with large surface areas and abundant porous structures was prepared by a hydrothermal synthesis method, which served as a novel support to enhance the catalytic properties of noble metal catalysts for the solvent-free selective oxidation of benzyl alcohol. The as-prepared samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, Fourier transform infrared (FTIR) spectroscopy, and Brunauer-Emmett-Teller (BET) method. The results clearly showed that the introduced N-containing group prevented the aggregation of graphene sheets and provided more structural defects to maximize the number of exposed active sites. The three-dimensional structure can provide a unique porous structure and large specific surface area. Moreover, the three-dimensional structure makes the recycling and reuse of the catalyst easier. The combination of these properties results in the reduction of the average particle size of metal palladium to 3.2 nm; this significantly increases the catalytic activity of the catalyst. The three-dimensional N-doped graphene aerogel-supported Pd nanoparticle (3D Pd/NRGO) composites exhibit excellent catalytic activity for the solvent-free selective oxidation of benzyl alcohol to benzaldehyde by molecular oxygen at 90 °C for 3 hours under atmospheric pressure, resulting in a 72.2% conversion of benzyl alcohol with 94.5% selectivity for benzaldehyde. In addition, the catalytic efficiency shows no obvious loss even after six repeated cycles. Thus, 3D Pd/NRGO can be used as an efficient, easily separable, recyclable, and stable catalyst for the solvent-free selective oxidation of benzyl alcohol under relatively mild conditions.
在此，通过水热合成法制备了具有大表面积和丰富多孔结构的三维（3D）氮掺杂石墨烯，其作为一种新型载体，用于增强贵金属催化剂对苯甲醇无溶剂选择性氧化的催化性能。通过X射线衍射（XRD）、扫描电子显微镜（SEM）、透射电子显微镜（TEM）、X射线光电子能谱（XPS）、拉曼光谱、傅里叶变换红外（FTIR）光谱和布鲁诺尔-埃米特-泰勒（BET）法对所制备的样品进行了表征。结果清楚地表明，引入的含氮基团阻止了石墨烯片的聚集，并提供了更多的结构缺陷，以最大限度地增加暴露的活性位点数量。三维结构可以提供独特的多孔结构和大比表面积。此外，三维结构使催化剂的回收和再利用更加容易。这些特性的结合导致金属钯的平均粒径减小到3.2 nm；这显著提高了催化剂的催化活性。三维氮掺杂石墨烯气凝胶负载钯纳米颗粒（3D Pd/NRGO）复合材料在90℃、常压下，通过分子氧对苯甲醇进行无溶剂选择性氧化制备苯甲醛，表现出优异的催化活性，3小时内苯甲醇的转化率为72.2%，对苯甲醛的选择性为94.5%。此外，即使经过六次重复循环，催化效率也没有明显损失。因此，3D Pd/NRGO可作为一种高效、易于分离、可回收且稳定的催化剂，用于在相对温和的条件下对苯甲醇进行无溶剂选择性氧化。
