Lou Diming, Xiang Beihong, Zhang Yunhua, Fang Liang, Tan Piqiang, Hu Zhiyuan
School of Automotive Studies, Tongji University, No. 4800, Cao'an Road, Shanghai 200092, China.
ACS Omega. 2023 Jun 2;8(23):20834-20844. doi: 10.1021/acsomega.3c01543. eCollection 2023 Jun 13.
Soot particles in engine exhaust seriously pollute the atmosphere and endanger human health. For soot oxidation, Pt and Pd precious metal catalysts are widely used and are effective. In this paper, the catalytic characteristics of catalysts with different Pt/Pd mass ratios for soot combustion were studied through X-ray diffraction, X-ray photoelectron spectroscopy (XPS), Brunauer-Emmett-Teller analysis, scanning electron microscopy, transmission electron microscopy, the temperature-programmed oxidation reaction, and thermogravimetry. Besides, the adsorption characteristics of soot and O on the catalyst surface were explored by density functional theory (DFT) calculations. The research results showed that the activity of catalysts for soot oxidation from strong to weak is Pt/Pd = 10:1, Pt/Pd = 5:1, Pt/Pd = 1:0, and Pt/Pd = 1:1. XPS results showed that the concentration of oxygen vacancies in the catalyst is the highest when the Pt/Pd ratio is 10:1. The specific surface area of the catalyst increases first and then decreases with the increase of Pd content. When the Pt/Pd ratio is 10:1, the specific surface area and pore volume of the catalyst reach the maximum. The following are the DFT calculation results. With the increase of Pd content, the adsorption energy of particles on the catalyst surface decreases first and then increases. When the Pt/Pd ratio is 10:1, the adsorption of C on the catalyst surface is the strongest, and the adsorption of O is also strong. In addition, this surface has a strong ability to donate electrons. The theoretical simulation results are consistent with the activity test results. The research results have a guiding significance for optimizing the Pt/Pd ratio and improving the soot oxidation performance of the catalyst.
发动机尾气中的碳烟颗粒严重污染大气并危害人类健康。对于碳烟氧化，铂和钯贵金属催化剂被广泛使用且效果显著。本文通过X射线衍射、X射线光电子能谱（XPS）、布鲁诺尔-埃米特-泰勒分析、扫描电子显微镜、透射电子显微镜、程序升温氧化反应和热重分析等方法研究了不同Pt/Pd质量比的催化剂对碳烟燃烧的催化特性。此外，还通过密度泛函理论（DFT）计算探索了碳烟和氧气在催化剂表面的吸附特性。研究结果表明，催化剂对碳烟氧化的活性由强到弱依次为Pt/Pd = 10:1、Pt/Pd = 5:1、Pt/Pd = 1:0和Pt/Pd = 1:1。XPS结果表明，当Pt/Pd比为10:1时，催化剂中氧空位的浓度最高。催化剂的比表面积随钯含量的增加先增大后减小。当Pt/Pd比为10:1时，催化剂的比表面积和孔体积达到最大值。以下是DFT计算结果。随着钯含量的增加，颗粒在催化剂表面的吸附能先减小后增大。当Pt/Pd比为10:1时，碳在催化剂表面的吸附最强，氧的吸附也很强。此外，该表面具有很强的电子给予能力。理论模拟结果与活性测试结果一致。研究结果对优化Pt/Pd比和提高催化剂的碳烟氧化性能具有指导意义。
