Abstract:

The interfacial sites between Pt and promoters are highly conducive to the selective oxidation of glycerol to 1,3-dihydroxyacetone (DHA). In this study, two Pt-based catalysts with different Pt-Bi interfacial structures, Pt/Bi₂O₃-CNTs and PtBi/CNTs, were prepared by using atomic layer deposition and impregnation-reduction method, respectively. The selective oxidation of glycerol on the two catalysts was investigated through a combination of experiments and density functional theory (DFT) calculations. Characterization results show that there is a relatively uniform Pt-Bi₂O₃ interface structure in the Pt/Bi₂O₃-CNTs catalyst, while the PtBi/CNTs catalyst forms a Pt₁Bi₁ intermetallic compound. Both catalysts promote the preferential oxidation of the secondary hydroxyl group in glycerol. Comparatively, the Pt/Bi₂O₃-CNTs catalyst demonstrates superior glycerol oxidation activity due to its smaller particle size and higher Pt⁰ 4f binding energy, whereas the PtBi/CNTs catalyst facilitates the deep oxidation of DHA. Furthermore, DFT calculations reveal that the rate-determining step for the oxidation of the secondary hydroxyl group of glycerol to DHA on both catalysts is C—H bond cleavage, with a relatively lower energy barrier observed on the Pt/Bi₂O₃-CNTs catalyst, resulting in higher reaction activity. On the surface of the PtBi/CNTs catalyst, DHA exhibits greater adsorption affinity, rendering it more susceptible to deep oxidation. The insights provided here could serve as a guide for the design and optimization of Pt-based catalysts for the selective oxidation of glycerol to DHA.

Key words: glycerol, oxidation, Pt-based catalyst, interface, molecular simulation

摘要：

通过原子层沉积（ALD）技术和浸渍-还原法，分别制备了两种具有不同Pt-Bi界面结构的Pt基催化剂：Pt/Bi₂O₃-CNTs和PtBi/CNTs，结合实验和密度泛函理论（DFT）计算比较研究了两种催化剂上甘油选择性氧化反应行为。表征结果显示，Pt/Bi₂O₃-CNTs催化剂中存在相对均一的Pt-Bi₂O₃界面结构，而PtBi/CNTs催化剂则形成了Pt₁Bi₁金属间化合物。活性评价实验发现，两种催化剂均促进了甘油仲羟基的优先氧化；相对而言，Pt/Bi₂O₃-CNTs催化剂由于具有较小的粒径和较高的Pt⁰ 4f结合能从而表现出较好的甘油氧化反应活性，PtBi/CNTs催化剂会导致产物1，3-二羟基丙酮（DHA）的深度氧化。进一步的DFT计算结果表明，两种催化剂上甘油仲羟基氧化生成DHA过程的决速步骤均为仲碳上C—H键断裂反应，Pt/Bi₂O₃-CNTs催化剂上该步骤的能垒相对较低，因而表现出更高的反应活性；PtBi/CNTs催化剂表面，DHA较容易吸附，因此更易被深度氧化。

关键词: 甘油, 氧化, Pt基催化剂, 界面, 分子模拟