Detailed Description of Pulse Isotopic Exchange Method for Analyzing Oxygen Surface Exchange Behavior on Oxide Ion Conductors  

用于分析氧离子导体的氧表面交换行为的脉冲同位素交换方法（英文）

作　　者：Chun-lin Song Jian-xin Yi Yan Yan 宋春林;易建新;严岩(西南大学材料与能源学院,重庆400715;中国科学技术大学安全科学与工程系,火灾科学国家重点实验室,合肥230026)

机构地区：[1]School of Materials and Energy, Southwest University, Chongqing 400715, China [2]State Key Laboratory of Fire Science, Department of Safety Science and Engineering, University of Science and Technology of China, Hefei 230026, China

出　　处：《Chinese Journal of Chemical Physics》2019年第4期474-484,I0003,共12页化学物理学报（英文）

摘　　要：A novel pulse 18O-16O isotopic exchange (PIE) technique for measurement of the rate of oxygen surface exchange of oxide ion conductors was presented. The technique employs a continuous flow packed-bed micro-reactor loaded with the oxide powder. The isothermal response to an 18O-enriched pulse passing through the reactor, thereby maintaining chemical equilibrium, is measured by on-line mass spectrometry. Evaluation of the apparent exchange rate follows from the uptake of 18O by the oxide at given reactor residence time and surface area available for exchange. The developed PIE technique is rapid, simple and highly suitable for screening and systematic studies. No rapid heating/quenching steps are required to facilitate 18O tracer anneal or analysis, as in other commonly used techniques based upon oxygen isotopic exchange. Moreover, the relative distribution of the oxygen isotopologues 18O2, 16O18O, and 16O2 in the effluent pulse provides insight into the mechanism of the oxygen exchange reaction. The PIE technique has been demonstrated by measuring the exchange rate of selected oxides with enhanced oxide ionic conductivity in the range of 350?900 oC. Analysis of the experimental data in terms of a model with two consecutive, lumped steps for the isotopic exchange reaction shows that for mixed conductors Ba0.5Sr0.5Co0.8Fe0.2O3-δ(BSCF) and La2NiO4+δ the reaction is limited by the apparent rate of dissociative adsorption of O2 molecules at the oxide surface. For yttria-stabilized zirconia (YSZ), a change-over takes place, from rate-limitations by oxygen incorporation below ∽800 oC to rate-limitations by O2 dissociative adsorption above this temperature. Good agreement is obtained with exchange rates reported for these materials in literature.

关 键 词：Isotopic exchange Oxygen surface exchange Ion conductor Ba0.5Sr0.5Co0.8Fe0.2O3-δ 

分 类 号：O643.1[理学—物理化学]