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We present a computational screening study of ternary metal borohydrides for reversible hydrogen storage based on density functional theory. We investigate the stability and decomposition of alloys containing 1 alkali metal atom, Li, Na, or K (M(1)); and 1 alkali, alkaline earth or 3d/4d transition metal atom (M(2)) plus two to five (BH(4))(-) groups, i.e., M(1)M(2)(BH(4))(2-5), using a number of model structures with trigonal, tetrahedral, octahedral, and free coordination of the metal borohydride complexes. Of the over 700 investigated structures, about 20 were predicted to form potentially stable alloys with promising decomposition energies. The M(1)(Al/Mn/Fe)(BH(4))(4), (Li/Na)Zn(BH(4))(3), and (Na/K)(Ni/Co)(BH(4))(3) alloys are found to be the most promising, followed by selected M(1)(Nb/Rh)(BH(4))(4) alloys.

The electrochemical stability of ionic liquids based on the 1-ethyl-3-methyl imidazolium [EMIM](+) cation and three different anions, dicyanoamide ([N(CN)(2)](-)), tricyanomethanide ([C(CN)(3)](-)) and tetracyanoborate ([B(CN)(4)](-)), has been investigated. Cyclic voltammetry, X-ray photoelectron spectroscopy (XPS) of the valence band, as well as density functional theory (DFT) calculations were performed. A clear dependence of the anodic stability on the anion can be observed by cyclic voltammetry which is confirmed by XPS valence band spectra. The experimental data are in good agreement with DFT calculations. The valence band spectra and the DFT calculations of the ionic liquids show energetic differences in the position of the highest occupied molecular orbital state and confirm the electrochemically measured stability following the sequence [EMIM][B(CN)(4)] > [EMIM][N(CN)(2)] > [EMIM][C(CN)(3)]. (C) 2012 The Electrochemical Society. [DOI: 10.1149/2.001207jes] All rights reserved.