CO_2毒化对Pd膜表面状态与氢同位素渗透性能的影响

Effect of CO_2 Poison on the Surface Phase and the Hydrogen Isotope Permeation Capacity of Pd Membrane

在不同温度的CO2气氛中对Pd膜进行了毒化,将毒化后的Pd膜与氢气反应并测试其氢同位素渗透性能。采用XPS、SEM等检测了CO2在不同温度下对Pd膜毒化后的表面成分与形貌,并对比分析了吸氢前、后的Pd膜表面状态的变化,得出了CO2对Pd膜表面状态的影响规律,探讨了CO2气体的毒化机理。结果表明,CO2分子在Pd表面会解离成为C=O,C-O与O原子,随着温度升高,C=O减少,而C-O与O原子含量增加。当CO2毒化温度达到500℃时,Pd表面会生成PdO并伴有微孔出现,而C-O随温度升高能够稳定吸附于Pd表面。毒化后的试样在常温下进行吸氢反应后表面PdO消失,吸附O含量减少,多孔形貌得到改变。CO2毒化后,由于C-O与O原子在Pd表面吸附并占据了Pd膜表面的氢解离位,从而导致Pd膜透氘能力下降。

The poison of Pd membrane in CO2 at different temperatures and the hydrogenization of the poisoned membrane were carried out in a silica tubular furnace and the hydrogen isotope permeation capacity was tested.The variation of Pd membrane phase and morphology was analyzed and observed by XPS and SEM.The cause and the mechanism of the variation were discussed.The results show that the molecule CO2 will dissociate to C=O,C-O and O on Pd membrane surface.The adsorptive capacity of C-O and O increases and that of C=O decreases with increasing of the temperature.PdO and micropores can be detected apparently when the poison temperature reaches 500 oC,and C-O will be adsorbed on Pd membrane surface firmly.After hydrogenization,the PdO,C-O and free O on the Pd surface vanish while C=O reappear.After the Pd membrane is poisoned by CO2,the hydrogen isotope permeation capacity of Pd membrane decreases because the atom O and C-O occupy H site and react with atom H easily.