Hydrogen permeation through surface modified Pd and PdAg membranes
Hydrogen permeation through surface modified Pd and PdAg membranes
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DOI：
10.1016/s0376-7388(01)00414-8
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发表时间：
2001-10
影响因子：
9.5
通讯作者：
H. Amandusson;Lars-Gunnar Ekedahl;H. Dannetun
中科院分区：
文献类型：
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作者：
H. Amandusson;Lars-Gunnar Ekedahl;H. Dannetun
在100~350℃温度范围内，研究了表面修饰的Pd和Pd70Ag30膜对氢的渗透。在厚度为25μm的Pd和Pd70Ag30膜上蒸镀银，以研究表面组成与膜的整体组成的比较。基于Pd70Ag30的膜在温度低于200°C时具有最大的渗透速率，而在上游蒸发了20ä银的Pd膜在200°C以上的渗透速率最大。因此，在200°C以上和200°C以下有不同的速率限制过程：在200℃以下，通过膜的整体扩散是速率限制的，而在200℃以上，表面成分的影响开始变得显著。进一步得出结论：当纯Pd膜表面朝向上游时，从表面到本体的急剧的银浓度梯度对于200°C以上的氢渗透速率是重要的。在氢气供应中加入氧气将几乎完全抑制氢渗透速率，而对于含银表面，氧气的存在几乎没有影响。在干净的Pd表面上，氧气在水形成反应中有效地消耗了吸附的氢。由于银在表面，没有检测到水的形成。钴供应的CO以类似的方式抑制氢在所有被研究的膜表面上的渗透，与表面银含量无关。
The hydrogen permeation through surface modified Pd and Pd70Ag30membranes has been studied at temperatures between 100 and 350°C. Silver has been evaporated on Pd and Pd70Ag30foils with a thickness of 25μm in order to study the role of the surface composition in comparison with the membrane bulk composition. The Pd70Ag30-based membranes display the largest permeation rates at temperatures below 200°C, while Pd membranes with 20Å silver evaporated on the upstream side show the largest permeation rates above 200°C. There are, consequently, different rate limiting processes above and below 200°C: at temperatures below 200°C, the bulk diffusion through the membrane is rate limiting, while at temperatures above 200°C, the influence of the surface composition starts to become significant. It has further been concluded that a sharp silver concentration gradient from the surface to the bulk is important for the hydrogen permeation rate at temperatures above 200°C. Adding oxygen to the hydrogen supply will almost totally inhibit the hydrogen permeation rate when a pure Pd membrane surface is facing the upstream side, while for silver-containing surfaces the presence of oxygen has almost no effect. On a clean Pd surface, oxygen effectively consumes adsorbed hydrogen in a water forming reaction. With Ag on the surface, no water formation is detected. Co-supplied CO inhibits the permeation of hydrogen in a similar manner on all studied membrane surfaces, independent of surface silver content.