Insights into Hydrogen Gas Environment-Promoted Nanostructural Changes in Stressed and Relaxed Palladium by Environmental Transmission Electron Microscopy and Variable-Energy Positron Annihilation Spectroscopy.
Insights into Hydrogen Gas Environment-Promoted Nanostructural Changes in Stressed and Relaxed Palladium by Environmental Transmission Electron Microscopy and Variable-Energy Positron Annihilation Spectroscopy.
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DOI：
10.1021/acs.jpclett.8b02363
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发表时间：
2018-08
期刊：
影响因子：
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通讯作者：
V. Roddatis;M. D. Bongers;R. Vink;V. Burlaka;J. Čížek;A. Pundt
中科院分区：
文献类型：
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作者：
V. Roddatis;M. D. Bongers;R. Vink;V. Burlaka;J. Čížek;A. Pundt
利用环境透射电子显微镜（ETEM）和可变能量正电子湮没谱（VEPAS）研究了在金红石型TiO2衬底上生长的无应力钯（Pd）薄膜和应力Pd薄膜的氢致微结构变化。Pd的微观结构变化强烈地依赖于氢压力和应力状态。在室温下，增强的Pd表面原子迁移率和表面重构已经在低氢压（pH <10 Pa）下通过ETEM观察到。观察结果与分子动力学模拟结果一致。一个强烈的增加的空位密度被发现，所谓的过剩空位被确定为VEPAS。在较高的压力下，迁移和消失的本征缺陷中观察到Pd独立箔。Pd薄膜的位错密度随着氢气压力的增加而增加。两个研究系统的比较表明，机械应力对Pd催化剂的结构演变的影响。
Environmental transmission electron microscopy (ETEM) and variable-energy positron annihilation spectroscopy (VEPAS) are used to observe hydrogen-induced microstructural changes in stress-free palladium (Pd) foils and stressed Pd thin films grown on rutile TiO2 substrates. The microstructural changes in Pd strongly depend on the hydrogen pressure and on the stress state. At room temperature, enhanced Pd surface atom mobility and surface reconstruction is seen by ETEM already at low hydrogen pressures ( pH < 10 Pa). The observations are consistent with molecular dynamics simulations. A strong increase of the vacancy density was found, and so-called superabundant vacancies were identified by VEPAS. At higher pressures, migration and vanishing of intrinsic defects is observed in Pd free-standing foils. The Pd thin films demonstrate an increased density of dislocations with increase of the H2 pressure. The comparison of the two studied systems demonstrates the influence of the mechanical stress on structural evolution of Pd catalysts.