Supplementary Information

Direct Synthesis of NaBH4 Nanoparticles from NaOCH3 for Hydrogen Storage

Ting Wang† and Kondo-Francois Aguey-Zinsou*,†

†MERLin, School of Chemical Engineering, The University of New South Wales, Sydney NSW 2052, Australia, E-mail: f.aguey-unsw.edu.au

Table S1. Synthesis methods of NaBH4.

Reaction Synthesis and products Yield Ref. Synthesis: React in ether, such as ethyl ether in which NaBH4 is not soluble. 2Na+2B2H6 → NaBH4+NaB3H6 Products: Mixture of NaBH4 and NaB3H6 -- [1,2] with intermediates of empirical composition Na2B2H6 and NaB2H6. Synthesis: Stir approximate proportions of 4Na+2H2+B(OCH3)3 → Na and B(OCH3)3 under H2 pressure at 15% [3,4] NaBH4+3NaOCH3 about 250 °C Synthesis: Disperse Na on finely divided NaCl, add H2 and BCl3, then heat the mixture to 150-170 °C 4Na+2H2+BCl3 → NaBH4+3NaCl Products: NaBH4 is recovered in 75% yield 75% [1] after heating for 3 h. Some diborane and pentaborane are also present as side products. Synthesis: React in ethereal solvents, such as Quantitative 2NaH+B2H6 diglyme 2NaBH4 the glymes, especially diglyme in which [1] yields NaH is more soluble. NaH+B(OCH3)3 → NaBH(OCH3)3 Synthesis: B2H6 react rapidly and Quantitative 2NaBH(OCH3)3+ B2H6 → quantitatively with NaH in the presence of [1] yields 2NaBH4+2B(OCH3)3 B(OCH3)3

90-96% Synthesis: Add methyl borate slowly to an purity excess of a well stirred mass of sodium 4NaH+B(OCH3)3 → NaBH4+3NaOCH3 hydride powder at 225-275 °C. 86-94% Products: NaBH4 may be extracted by liquid yields ammonia or primary amines, such as [1,3, isopropylamine. 5]

3NaH+NaBH(OCH3)3 → Methyl borate may be replaced by NaBH4+3NaOCH3 78% NaBH(OCH3)3, NaB(OCH3)4 or ethyl and n- 4NaH+NaB(OCH3)4 → 66% butyl borate NaBH4+4NaOCH3 -- 4NaH+B(OC2H5)4 → NaBH4+3NaOC2H5 Synthesis: Heat and grind NaH with 4NaH+2B2O3→NaBH4+3NaBO2 60% [3] B2O3 at 330-350 °C for 20 to 48 h 8NaH+2H3BO3+3CO2 → -- -- [1] 2NaBH4+3Na2CO3+6H2O

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2NaBH(OCH3)3+B2H6 → 2NaBH4+2B(OCH3)3 Synthesis: Pass B2H6 directly from a generator through a column of solid 90% [1,6] 3NaBH(OCH3)3+2B2H6 → NaBH(OCH3)3. 3NaBH4+4B(OCH3)3 4NaBH(OCH3)3 THF/diglyme Synthesis: NaBH(OCH3)3 decompose NaBH4+3NaB(OCH3)4 90~95% [7] rapidly in THF and diglyme

3NaOCH3+2B2H6 → 3NaBH4+B(OCH3)3 Synthesis: React rapidly and quantitatively [1,3, 90% in the absence of solvent. 5] 3NaB(OCH3)4+2B2H6 → 3NaBH4+4B(OCH3)3 Synthesis: Heat 4NaBH(OCH3)3 at 250-255

°C in the evacuated glass liner of a small

Aminxo hydrogenator for 2 h. Not Products: Only partial NaBH(OCH3)3 were [3] satisfactory disproportionated to NaBH4 and 4NaBH(OCH3)3 → 3NaB(OCH3)4, NaBH4 can be extracted by NaBH4+3NaB(OCH3)4 liquid ammonia. NaB(OCH3)4+SiH4 → Synthesis: Add SiH4 to NaB(OCH3)4 in -- [1] NaBH4+Si(OCH3)4 tetrahydrofuran or diglyme. 3NaB(OCH3)4+4Al+6H2 → Synthesis: React in diglyme. -- [1] 3NaBH4+4Al(OCH3)3 Synthesis: NaBH4 is formed when Na2B4O7 Na2B4O7+16Na+8H2+7SiO2 → is treated at 300-500 °C under H2 pressure -- [1] 4NaBH4+7Na2SiO3 (3-5 atm) with Na in the presence of SiO2. 4NaH+(CH3)3N·BCl3 → Synthesis: React NaH with (CH3)3N·BCl3 in -- [1] NaBH4+3NaCl+(CH3)3N diglyme. Synthesis: Require high temperature (400- (Na2B4O7+7SiO2)+16Na+8H2 → 500 °C) and hydrogen pressure. [8,9] 4NaBH4+7Na2SiO3 Products: Isolation of NaBH4 involves extraction with liquid NH3 under pressure. NaBO2+2MgH2 → NaBH4+MgO

Synthesis: (a) The reaction of NaBO2 and MgH2 was carried out at 550 °C under 7 [10,1 MPa of H2 pressure for 2h. ~100% 1] (b) NaBH4 can be also obtained by milling NaBO2 and MgH2 at room temperature.

Na2B4O7+NaCO3+8MgH2 → 4NaBH4+8MgO+CO2 NaBO2+2CaH2→NaBH4+CaO Synthesis: The reaction of NaBO2 mixed NaBO2+MgSi+2H2 → NaBH4+2MgO+Si with Si was carried out at 400-550 °C under -- [11] 7 MPa of H2 pressure for 2h.

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Figure S1. TEM images of purified NaOCH3.

Figure S2. XRD patterns of the purified NaOCH3 and the as-synthesized NaOCH3 nanoparticles.

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Figure S3. FTIR spectra of the purified NaOCH3 and the as-synthesized NaOCH3 nanoparticles.

Figure S4. FTIR spectrum of the pristine octadecylamine.

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Figure S5. TGA under Ar of pristine octadecylamine.

Figure S6. (a) TGA/DSC under Ar of commercial NaBH4; (b) H2 desorption from commercial NaBH4

recorded by mass spectrometry and selected mass corresponding to the release of B2H6.

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