Interactions of Y and Cu on Mg2Ni type hydrogen storage alloys: A study based on experiments and density functional theory calculation

• Published in: International journal of hydrogen energy 2020-10, Vol.45 (53), p.28974-28984
• Main Authors: Sun, Hao, Gao, Xueyun, Zhao, Fengguang, Li, Yiming, Zhang, Yanghuan, Ren, Huiping
• Format: Article
• Language: English
• Subjects: Dehydrogenation; Density functional theory; Hydrogen storage alloys; Mg–Ni alloys
• ISSN: 0360-3199; 1879-3487
• DOI: 10.1016/j.ijhydene.2020.07.167

Evolution of microstructure and hydrogen storage performances were studied in a Y substituted Mg24Ni10Cu2 hydrogen storage alloy. Interactions of Y and Cu on the phase structure and hydrogen storage properties were explore. Substitution by Y refined the microstructure and yield existence of YMgNi4. Furthermore, Y addition promoted the replacement of Cu for Ni in the Mg2Ni.The study of the alloy's dehydrogenation performance and mechanism showed that the addition of Y did not alter the mechanism of random nucleation and subsequent growth, but reduced the activation energy of the dehydrogenation of the alloy from 77.4 kJ/mol to 67.6 kJ/mol. The thermodynamic energy of the dehydrogenation was also improved, and the enthalpy change (ΔH) and entropy change (ΔS) of the Mg2NiH4 phase decreased from 67.1 J/K/mol H2 and 123.1 J/K/mol H2 to 61.1 J/K/mol H2 and 115.4 J/K/mol H2, respectively. Furthermore, the density functional theory calculation showed that the addition of Y promoted the substitution of Cu for Ni, further reduced the stability of the main hydride Mg2NiH4, facilitated the release of hydrogen, and reduced the ΔH and ΔS of the hydride dehydrogenation. •Y promotes the substitution of Cu for Ni in Mg2(Ni, Cu).•Kinetic and thermodynamic hydrogenation properties were dramatically improved by adding Y.•Y reduces the stability of the hydride by weakening the binding energy.