Stability of Metal Borohydrides

Y. Nakamori, K. Miwa, A. Ninomiya, H. Li, N. Ohba, S.-l. Towata, A. Ziittel, S.-l. Orimo, Correlation between thermodynamical stabilities of metal borohydrides and cation electronegatives First principles calculations and experiments , Phys. Rev. B 74 (2006) 45126. 

K. Miwa, N. Ohba, S. Towata, Y. Nakamori, A. Ztittel, S. Orimo, First-principles study on thermodynamical stability of metal borohydrides Aluminum borohydride A1(BH )2 , J. Alloys Compd. 446-447 (2007) 310-314. 

The thermodynamic stabilities for the series of metal borohydrides M(BH4) (M = Li, Na, K, Mg, Ca, Sc, Zr, Hf, Cu, Zn and Al n = -4) have been systematically investigated by first-principles calculations.The heat of formation of M(BH4) AT/boro were estimated from the difference of the total energies between the left- and right-hand sides of Eq. (15.23) ... 

Li H-W, Orimo S, Nakamori Y, Miwa K, Ohba N, Towata S and Ziittel A (2007), Materials designing of metal borohydrides viewpoints from thermodynamical stabilities, J. Alloys Compounds, 446-447, 315-318. 

Li, H.-W. Orimo, S. Nakamori, Y. Miwa, K. Ohba, N. Towata, S. ZtitteL A., Materials designing of metal borohydrides Viewpoints fiom thermodynamical stabilities, J. Alloys Compd. 2007,446-447,315-318. 

Metal nanoparticles are synthesized by reduction of metal ions using reducing agents such as borohydride, amines, and 1,2-diols in the presence of stabilizing agents, typically long-chain alkyl thiols (e.g., dodecanethiol), amines,... 

Figure 2 Biomimetic synthesis strategy for peptide encapsulated nanoclusters. Synthesis begins with complexation of peptide hgand to metal ion, followed by borohydride reduction of metal complex, nucleation, and formation of peptide stabilized nanocluster. (Reprinted with permission from Ref. 1. 2003 American Chemical Society)...

The thermal desorption temperature Td of M(BH4) determined using gas chromatography was also closely correlated with Xp [20], as shown in Fig. 1. Td (closed circles) decreases with an increase in the value of Xp- Therefore, we conclude that the value of Xp of the cation (metal) is an indicator that assists in the estimation of the thermodynamical stabilities of single-cation borohydrides M(BH4) with the corresponding value of Td in various temperature ranges. 

In this study, we examine the thermodynamical stabilities of double-cation borohydrides MM (Q Td) , and then we verify whether the correlation between Td and Xp determined for single-cation borohydrides can be reasonably extended also to double-cation ones. (The possible extended correlation might lead to precise adjustments of the thermodynamical stabilities of borohydrides, which is considered to be difficult in case of single-cation borohydrides due to the discrete value of Xp of each cation (metal).) For the abovementioned purpose, we propose (xp = 1.4, Td of Zr(BH4)4 is approximately 440 K) and Li ... 

The electronic stmctures indicate that the charge transfer from metal cations M" to (BH4) anions is a key feature for the stability of borohydrides, M(BH4) . 

In order to compare the stability of borohydrides composed of the metal cations M which have different valencies, AT/boro values were normalized by the number of BH4 tetrahedra in the formula unit. As shown in Section... 

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