本文探讨了全氧化态和高度还原CeO2(111)表面醋醛（CH3CHO）的温度依赖吸附及反应行为。在全氧化表面，醋醛通过羰基O与四价铈离子形成弱相互作用，低温下吸附，210K脱附未反应。而在高度还原表面，低温出现新的振动特征，经红外光谱和DFT计算确认为两分子醋醛形成的偶极态，此状态在400K前稳定，随后分解为乙醛醇形式。计算揭示的反应活化能与之前报道的TPD数据相符，强调了表面氧化态对醋醛催化反应的重要影响。
摘要：
The temperature-dependent adsorption and reaction ofacetaldehyde(CH3CHO) on a fully oxidized and a highly reduced thin-filmCeO2(111) surface have been investigated using a combinationof reflection–absorption infrared spectroscopy (RAIRS) andperiodic density functional theory (DFT+U) calculations. On the fullyoxidized surface, acetaldehyde adsorbs weakly through its carbonylO interacting with a lattice Ce4+ cation in the η1-O configuration. This state desorbs at 210 K without reaction.On the highly reduced surface, new vibrational signatures appear below220 K. They are identified by RAIRS and DFT as a dimer state formedfrom the coupling of the carbonyl O and the acyl C of two acetaldehydemolecules. This dimer state remains up to 400 K before decomposingto produce another distinct set of vibrational signatures, which areidentified as the enolate form of acetaldehyde (CH2CHO).Furthermore, the calculated activation barriers for the coupling ofacetaldehyde, the decomposition of the dimer state, and the recombinativedesorption of enolate and H as acetaldehyde are in good agreementwith previously reported TPD results for acetaldehyde adsorbed onreduced CeO2(111) [Chen et al. (111) surface and play a crucial role in stabilizingand activating acetaldehyde for coupling reactions.
展开
扫一扫
被折叠的 条评论
为什么被折叠?
到【灌水乐园】发言
