Department of Chemistry, University of Johannesburg , PO Box 524, Auckland Park 2006, Johannesburg, South Africa.
Langmuir. 2017 Jul 18;33(28):7086-7095. doi: 10.1021/acs.langmuir.7b00903. Epub 2017 Jul 3.
Herein we report on the catalytic activity of mesoporous nickel, iron, cerium, cobalt, and manganese oxides prepared using KIT-6 as a hard template via evaporation-assisted precipitation. The mesoporous metal oxides (MMOs) were characterized and used as heterogeneous catalysts in the reduction of 4-nitrophenol (4-Nip) by sodium borohydride (BH). Furthermore, polyamidoamide (PAMAM) dendrimers were used to synthesize gold-palladium nanoalloy particles. The size of AuPd/PAMAM was found to be 3.5 ± 0.8 nm in diameter before being immobilized on the aforementioned mesoporous metal oxides and used as catalysts in the reduction of 4-Nip. Prior to catalytic evaluation, the reduction profiles of the mesoporous metal oxides were investigated by hydrogen-temperature-programmed reduction (H-TPR) and showed that mesoporous metal oxides can be easily reduced at lower temperatures and that the immobilization of gold-palladium nanoalloy particles lowers their reduction temperatures. Mesoporous cobalt and manganese oxides showed catalytic activity toward 4-Nip reduction, and the activity was enhanced after immobilization of the gold-palladium nanoalloys. Isolation of nanoparticles activity was achieved by immobilization of the gold-palladium nanoalloys on the inert silica support. From this we postulated an electron relay mechanism for the reduction of 4-nitrophenol. With the use of power rate law we showed that 4-Nip reduction follows pseudo-first-order kinetics.
在此，我们报告了介孔镍、铁、铈、钴和锰氧化物的催化活性，这些氧化物是通过蒸发辅助沉淀法使用 KIT-6 作为硬模板制备的。介孔金属氧化物（MMO）进行了表征，并用作 4-硝基苯酚（4-Nip）通过硼氢化钠（BH）还原的多相催化剂。此外，还使用聚酰胺-胺（PAMAM）树枝状大分子合成了金钯纳米合金颗粒。在将 AuPd/PAMAM 固定在上述介孔金属氧化物上并用作 4-Nip 还原的催化剂之前，发现其直径为 3.5 ± 0.8nm。在进行催化评价之前，通过氢气程序升温还原（H-TPR）研究了介孔金属氧化物的还原曲线，结果表明介孔金属氧化物可以在较低的温度下容易地被还原，并且金钯纳米合金颗粒的固定降低了它们的还原温度。介孔钴和锰氧化物对 4-Nip 还原表现出催化活性，并且在固定金钯纳米合金后活性得到增强。通过将金钯纳米合金固定在惰性二氧化硅载体上，可以实现纳米粒子活性的分离。由此，我们提出了电子接力机制用于 4-硝基苯酚的还原。通过使用功率速率定律，我们表明 4-Nip 还原遵循准一级动力学。
