Electrochemical promotion of catalysis controlled by chemical potential difference across a mixed ionic-electronic conducting ceramic membrane – an example of wireless NEMCA
Electrochemical promotion of catalysis controlled by chemical potential difference across a mixed ionic-electronic conducting ceramic membrane – an example of wireless NEMCA
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通过混合离子电子导电陶瓷膜上的化学势差控制催化的电化学促进——无线 NEMCA 的一个例子
DOI：
10.1007/s11244-006-0136-0
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发表时间：
2007
影响因子：
3.6
通讯作者：
I. Metcalfe
中科院分区：
文献类型：
--
作者：
D. Poulidi;A. Thursfield;I. Metcalfe
在双室反应器中使用La0.6Sr0.4Co0.2F0.8O3混合离子电子导电（MIEC）膜来提高铂催化剂对乙烯氧化的催化活性。通过控制跨膜的氧化学势差，建立氧离子跨膜迁移并反向溢出到催化剂表面的驱动力。然后通过在催化剂表面上形成双层氧化物阴离子来促进反应。膜材料的电子传导性消除了对外部电路的需要，以将促进的氧化物离子物质泵送通过膜并到达催化剂表面。这使得这个“无线”系统更简单，更适合大规模的实际应用。初步实验表明，与惰性吹扫气体下的速率相比，在膜反应器的吹扫侧暴露于氧气气氛中，乙烯氧化的反应速率确实可以提高近一个数量级，从而在膜上产生氧化学势差。此外，当吹扫侧的氧气流停止时，速率不会返回到其初始未提升值，而是保持永久提升。对利用外部电路的经典电化学促进和利用化学势差的“无线”系统进行了一些比较。此外，还提出了“表面氧捕获”模型来解释催化剂活性的永久提升。
A La0.6Sr0.4Co0.2F0.8O3 mixed ionic electronic conducting (MIEC) membrane was used in a dual chamber reactor for the promotion of the catalytic activity of a platinum catalyst for ethylene oxidation. By controlling the oxygen chemical potential difference across the membrane, a driving force for oxygen ions to migrate across the membrane and backspillover onto the catalyst surface is established. The reaction is then promoted by the formation of a double layer of oxide anions on the catalyst surface. The electronic conductivity of the membrane material eliminates the need for an external circuit to pump the promoting oxide ion species through the membrane and onto the catalyst surface. This renders this “wireless” system simpler and more amenable for large-scale practical application. Preliminary experiments show that the reaction rate of ethylene oxidation can indeed be promoted by almost one order of magnitude upon exposure to an oxygen atmosphere on the sweep side of the membrane reactor, and thus inducing an oxygen chemical potential difference across the membrane, as compared to the rate under an inert sweep gas. Moreover, the rate does not return to its initial unpromoted value upon cessation of the oxygen flow on the sweep side, but remains permanently promoted. A number of comparisons are drawn between the classical electrochemical promotion that utilises an external circuit and the “wireless” system that utilises chemical potential differences. In addition a ‚surface oxygen capture’ model is proposed to explain the permanent promotion of the catalyst activity.