Systematic investigation on hydrogen storage properties of RNi5 (R: rare earth) intermetallic compounds with multi-plateau

✍ Scribed by H Senoh; N Takeichi; H.T Takeshita; H Tanaka; T Kiyobayashi; N Kuriyama

• Book ID: 103844369
• Publisher: Elsevier Science
• Year: 2004
• Tongue: English
• Weight: 104 KB
• Volume: 108
• Category: Article
• ISSN: 0921-5107
• DOI: 10.1016/j.mseb.2003.10.055

✦ Synopsis

We investigated the pressure-composition (P-C) isotherms of several binary RNi 5 (R = La, Ce, Pr, Nd, Sm and Gd) intermetallic compounds to clarify the correlation of the hydrogen storage properties between multi-plateaux. It was found that all RNi 5 compounds have similar P-C isotherms with two well-separated plateaux except for CeNi 5 , indicating that two hydrides with compositions of RNi 5 H 3-4 and RNi 5 H 6-7 are formed. With increasing the atomic number of R element in the RNi 5 compounds, the unit cell volume decreases due to the decrease of the radius of the R element. This influences the absolute enthalpies of dehydrogenation | H| of both hydrides (␤ and ␥) to decrease, which consequently leads to the increase of the second plateau pressure as well as the first plateau. Contrary to LaNi 5 -H 2 system, the | H| of ␥ hydride is smaller than that of | H| of ␤ hydride for the other systems, which indicates that the pressure gap between two plateau pressures expands with decreasing temperature. The second plateau tends to disappear with large atomic number of R element because the | H| value approaches to zero.