Lee Jae Hwan, Jo Deok Yeon, Choung Jin Woo, Kim Chang Hwan, Ham Hyung Chul, Lee Kwan-Young
Department of Chemical and Biological Engineering, Korea University, 145, Anam-Ro, Seongbuk-Gu, Seoul 02841, Republic of Korea.
Advanced Catalysts and Emission-Control Research Lab, Research & Development Division, Hyundai Motor Group, Hyundaiyeonguso-Ro, Namyang-Eup, Hwaseong-Si, Gyeonggi-Do 18280, Republic of Korea.
J Hazard Mater. 2021 Feb 5;403:124085. doi: 10.1016/j.jhazmat.2020.124085. Epub 2020 Sep 23.
The effects of noble metal (M = Ag, Au, Pd, Pt, and Rh) on CeO in enhancing the activity toward soot oxidation were studied through experimental methods and density functional theory (DFT) calculations. Each noble metal (3 mol.%) was supported on CeO (M/CeO) and the properties of the catalysts were verified by XRD, HRTEM, N physisorption, CO chemisorption, XPS, and H-TPR results. The noble metal was highly dispersed over CeO, except for Au due to the sintering of Au, and the reducibility of the catalysts was greatly improved according to degree of the interaction between each noble metal and CeO. The activities of M/CeO catalysts for soot oxidation were better than that of CeO, and followed the order Rh/CeO > Ag/CeO > Pt/CeO > Au/CeO > Pd/CeO > CeO. Moreover, our DFT calculations showed that vacancy formation energy was gradually lowered in the following order: CeO > Pd/CeO > Pt/CeO > Au/CeO = Ag/CeO > Rh/CeO, which was similar order with experimental activity. In addition, the electronic states of the p and f orbitals of CeO were studied to compare with the occupied Ce 4f electrons, which affect the redox property. Rh/CeO and Ag/CeO showed the improved soot oxidation activity, with an enhanced ability to generate oxygen vacancy formation and oxygen adsorption and increased electron transfer. Consequently, the experimental and DFT calculation results revealed the roles of noble metals on ceria with respect to catalytic activity.
通过实验方法和密度泛函理论（DFT）计算，研究了贵金属（M = 银、金、钯、铂和铑）对CeO在提高碳烟氧化活性方面的影响。每种贵金属（3摩尔%）负载在CeO上（M/CeO），并通过XRD、HRTEM、N物理吸附、CO化学吸附、XPS和H-TPR结果验证了催化剂的性能。除了由于金烧结导致的Au/CeO外，贵金属高度分散在CeO上，并且根据每种贵金属与CeO之间相互作用的程度，催化剂的还原性得到了极大提高。M/CeO催化剂对碳烟氧化的活性优于CeO，顺序为Rh/CeO > Ag/CeO > Pt/CeO > Au/CeO > Pd/CeO > CeO。此外，我们的DFT计算表明，空位形成能按以下顺序逐渐降低：CeO > Pd/CeO > Pt/CeO > Au/CeO = Ag/CeO > Rh/CeO，这与实验活性顺序相似。此外，研究了CeO的p和f轨道的电子态，以与影响氧化还原性质的占据的Ce 4f电子进行比较。Rh/CeO和Ag/CeO表现出改善的碳烟氧化活性，具有增强的产生氧空位形成和氧吸附的能力以及增加的电子转移。因此，实验和DFT计算结果揭示了贵金属在二氧化铈上对催化活性的作用。
