Enhanced hydrogen storage properties of a dual-cation (Li+, Mg2+) borohydride and its dehydrogenation mechanism. Issue 59 (25th July 2017)

• Record Type: Journal Article
• Authors: Zhang, Liuting; Zheng, Jiaguang; Xiao, Xuezhang; Fan, Xiulin; Huang, Xu; Yang, Xinlin; Chen, Lixin
• Is Part Of: RSC advances. Volume 7:Issue 59(2017)
• Page Start: 36852
• Page End: 36859
• Publication Date: 2017-07-25
• Subjects: Chemistry -- Periodicals; 540.5
• DOI: 10.1039/c7ra06599j
• Languages: English
• ISSNs: 2046-2069

Abstract

Abstract : The dehydrogenation temperature and kinetics of LiBH4 could be significantly modified by altering the χ p of Li ions. Abstract : In this paper, we present a new method to synthesize a dual-cation (Li +, Mg 2+ ) borohydride. It is found that Li–Mg–B–H is formed by mechanical milling a mixture of LiBH4 and MgCl2 with a molar ratio of 3 : 1 in diethyl ether (Et2 O) and a subsequent heating process. The morphology and structure of the as-prepared Li–Mg–B–H compound are studied by SEM, XRD, FTIR and NMR measurements. Further experiments testify that Li–Mg–B–H can release approximately 12.3 wt% of hydrogen under 4 bar initial hydrogen pressure from room temperature to 500 °C and reach a maximum desorption rate of 13.80 wt% per h at 375 °C, which is 30 times faster than that of pristine LiBH4 . Thermal analysis indicates that the decomposition process of the new compound involves three steps: (1) Li–Mg–B–H first decomposes into LiBH4 and MgH2 and synchronously releases a number of H2 molecules; (2) MgH2 decomposes to Mg and H2 ; (3) LiBH4 reacts with Mg, generating H2, MgB2 and LiH. Moreover, Li–Mg–B–H is proved to be partially reversible, which can release 5.3 wt% hydrogen in the second dehydrogenation process. The strategy of altering the χ p of metal ions in borohydrides may shed light on designing dual-cation borohydrides with better hydrogen storage performance.