Nielsen Jimmi, Skou Eivind M, Jacobsen Torben
Department of Energy Conversion and Storage, Technical University of Denmark, Frederiksborgvej 399, DK-4000 Roskilde (Denmark).
Institute of Chemical Engineering, Biotechnology and Environmental Technology, University of Southern Denmark Odense, Campusvej 55, DK-5230 Odense M. (Denmark).
Chemphyschem. 2015 Jun 8;16(8):1635-45. doi: 10.1002/cphc.201500025. Epub 2015 Mar 17.
Temperature-programmed desorption (TPD) with a carrier gas was used to study the oxygen sorption and desorption properties of oxidation catalysts and solid-oxide fuel cell (SOFC) cathode materials (La(0.85) Sr(0.15)0.95 MnO(3+δ) (LSM) and La(0.60) Sr(0.40) Fe(0.80) Mn(0.20) O(3-δ) (LSFM). The powders were characterized by X-ray diffractometry, atomic force microscopy (AFM), and BET surface adsorption. Sorbed oxygen could be distinguished from oxygen originating from stoichiometry changes. The results indicated that there is one main site for oxygen sorption/desorption. The amount of sorbed oxygen was monitored over time at different temperatures. Furthermore, through data analysis it was shown that the desorption peak associated with oxygen sorption is described well by second-order desorption kinetics. This indicates that oxygen molecules dissociate upon adsorption and that the rate-determining step for the desorption reaction is a recombination of monatomic oxygen. Typical problems with re-adsorption in this kind of TPD setup were revealed to be insignificant by using simulations. Finally, different key parameters of sorption and desorption were determined, such as desorption activation energies, density of sorption sites, and adsorption and desorption reaction order.
采用载气程序升温脱附（TPD）法研究了氧化催化剂和固体氧化物燃料电池（SOFC）阴极材料（La(0.85)Sr(0.15)0.95MnO(3 + δ) （LSM）和La(0.60)Sr(0.40)Fe(0.80)Mn(0.20)O(3 - δ) （LSFM））的氧吸附和解吸性能。通过X射线衍射、原子力显微镜（AFM）和BET表面吸附对粉末进行了表征。可以将吸附的氧与化学计量变化产生的氧区分开来。结果表明，存在一个主要的氧吸附/解吸位点。在不同温度下随时间监测吸附的氧量。此外，通过数据分析表明，与氧吸附相关的脱附峰可用二级脱附动力学很好地描述。这表明氧分子在吸附时发生解离，脱附反应的速率决定步骤是单原子氧的重组。通过模拟发现，这种TPD装置中典型的再吸附问题并不显著。最后，确定了吸附和解吸的不同关键参数，如脱附活化能、吸附位点密度以及吸附和解吸反应级数。
