First-principles investigation on the role of interstitial site preference on the hydrogen-induced disproportionation of ZrCo and its doped alloys |
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| Affiliation: | 1. School of Materials and Energy, Southwest University, Chongqing, 400715, PR China;2. College of Architecture and Environment, Sichuan University, Chengdu, 610065, PR China;3. China Academy of Engineering Physics, Mianyang, 621900, PR China;1. State Key Laboratory of Silicon Materials; School of Materials Science and Engineering, Zhejiang University, Hangzhou, 310027, PR China;2. Institute of Materials, China Academy of Engineering Physics, Mianyang, 621907, PR China;3. State Key Laboratory of Surface Physics and Chemistry, Mianyang 621907, PR China;4. Key Laboratory of Advanced Materials and Applications for Batteries of Zhejiang Province, Hangzhou, 310013, PR China;1. School of Materials and Energy, Southwest University, Chongqing 400715, PR China;2. College of Architecture and Environment, Sichuan University, Chengdu 610065, PR China;1. School of Mathematics and Physics, Anhui Jianzhu University, Hefei, 230601, PR China;2. Key Laboratory of Materials Physics, Institute of Solid State Physics, Chinese Academy of Sciences, P. O. Box 1129, Hefei, 230031, PR China;3. College of Science, Zhongyuan University of Technology, Zhengzhou, 450007, PR China;4. Shchool of Environmental and Energy Engineering, Key Laboratory of Anhui Province of Water Pollution Control and Wastewater Reuse, Anhui Jianzhu University, HeFei, China;1. Institute of Materials, China Academy of Engineering Physics, P. O. Box 9071-12, Mianyang 621907, China;2. Science and Technology on Surface Physics and Chemistry Laboratory, P. O. Box 9072-35, Mianyang 621908, China;3. State Key Laboratory of Silicon Materials, Zhejiang University, Hangzhou 310027, China;1. Science and Technology on Surface Physics and Chemistry Laboratory, Mianyang, 621907, China;2. Institute of Materials, China Academy of Engineering Physics, Mianyang, 621900, China;3. Research Institute for New Materials Technology, Chongqing University of Arts and Sciences, Yongchuan, Chongqing, 402160, China;1. Institute of Atomic and Molecular Physics, Sichuan University, 610065, Chengdu, China;2. College of Physics, Sichuan University, 610065, Chengdu, China;3. Science and Technology on Surface Physics and Chemistry Laboratory, P. O. Box 9071-35, Jiangyou, 621907, China;4. College of Mathematics, Sichuan University, 610065, Chengdu, China |
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| Abstract: | There are two phase structures involved in ZrCo hydrides (ZrCoHx). When x ≤ 1, the α-phase hydride is generated when hydrogen atoms occupy the 3c and 12i sites. When 1 < x ≤ 3, three interstitial sites of 4c2, 8f1, and 8e are occupied by H, and in turn the β-phase hydride is formed. There is a disproportionation reaction in β-phase hydrides during hydrogen discharging process to produce the ZrH2 phase with higher thermal stability, leading to inferior hydrogen storage performance. In this study, the influence of hydrogen storage capacity on thermodynamic and lattice stabilities of α- and β-phase hydrides for each occupancy position is investigated under the framework of the first-principles study. The results indicate that the binding energy in the 3c site is higher compared with the 12i site under the condition of identical hydrogen storage capacity. Similarly, the binding energy is the largest for the 8e site compared with the other two sites, indicating that there is the least energy released in the reaction process. Thus, the 8e site is proved as the most unfavorable site in β-phase ZrCo hydrides, which is due to its degraded thermodynamic stability. Also, comparisons of mechanical properties and total density of states for each site in two hydride phases are presented to demonstrate that compound lattice stability in the 8e site is the poorest, suggesting that it is more likely to produce disproportionation. Furthermore, the dependence of hydrogen storage performance of β-phase hydrides on Ti/Rh doping is examined as well. It is discovered that there is improved thermodynamic stability and lattice stability in the 8e site for Zr0.875Ti0.125Co after Zr is partially substituted by Ti, which significantly enhances the disproportionation resistance. In contrast, when Co is partially replaced by Rh, there is a deterioration in the thermodynamic stability of ZrCo0.875Rh0.125 in the 8e site, but its lattice stability is somewhat improved. |
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| Keywords: | ZrCo alloy Hydrogen storage Thermodynamic stability Lattice stability Doping |
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