Abstract
First-principles calculation was used to systematically investigate hydrogen solubility in Pd3Ag phases. It was found that the solubility of hydrogen in Pd3Ag phases was much greater than in face-centered cubic (FCC) Pd, suggesting that Ag atoms enhanced hydrogen solubility with respect to FCC Pd. In addition, the present calculation also revealed that the anti-site defect formation enthalpies of Pd3Ag were close to zero, and the values of vacancy were positive and large, which indicated that Pd3Ag distributed compactly. In the process of hydrogen separation, anti-site defects decreased the hydrogen solubility in the Pd3Ag phases, i.e., the ordered Pd3Ag phases bestowed excellent properties of H selectivity. The results presented not only explore the fundamental properties of Pd3Ag phases and their various potential applications, but also agree with experimental observations reported in the literature.
Highlights
In recent decades, Pd–Ag bimetallic systems have attracted significant research interest for their superior hydrogen (H) catalytic and separation properties [1,2,3,4], mainly due to their unique hydrogen selectivity and permeability [5,6]
The mechanism of hydrogen diffusion in Pd3 Ag phases has been reported by means of first-principles calculation [13]
By means of a highly accurate theoretical calculation based on density function theory (DFT), this study is aimed to systematically investigate the effects of point defects on hydrogen solubility in
Summary
Pd–Ag bimetallic systems have attracted significant research interest for their superior hydrogen (H) catalytic and separation properties [1,2,3,4], mainly due to their unique hydrogen selectivity and permeability [5,6]. As a typical hydrogen separation material, PdAg membranes with various Ag content have been the focus of attention. PdAg phases with 23–32% of Ag have an optimal performance in hydrogen permeation experiments [9,10,15]. There is a lack of further theoretical investigations on the effects of Pd3 Ag phases on H selectivity. Point defects have important effects on the physicochemical properties of PdAg phases and play a deleterious role in the performance of Pd3 Ag phases. As for the fundamental effects of point defects on H selectivity, there are no more results so far in the literature to the best of our knowledge
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