Supporting Information

Transcription

1 Supporting Information Copyright Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim, 2010 Growth of Crystalline Polyaminoborane through Catalytic Dehydrogenation of Ammonia Borane on FeB Nanoalloy Teng He, [a] Junhu Wang, [a] Guotao Wu, [a] Hyunjeong Kim, [b] Thomas Proffen, [b] Anan Wu, [c] Wen Li, [d] Tao Liu, [e] Zhitao Xiong, [a] Chengzhang Wu, [a] Hailiang Chu, [a] Jianping Guo, [a] Tom Autrey, [f] Tao Zhang, [a] and Ping Chen* [a] chem_ _sm_miscellaneous_information.pdf

2 1. TEM observation of the Fe-doped AB sample Figure S1 TEM image of the as prepared 5.0 mol % Fe-doped AB sample. Inserted is the magnified image. 2. TPD curves of AB with or without Fe doping Intensity (a.u.) Borazine H 2 5% Fe-AB neat AB neat AB 5% Fe-AB Intensity (a.u.) Temperature ( o C) Temperature ( o C) Figure S2 TPD/MS curves of the neat and 5.0 mol % Fe-doped AB samples. H 2 signal (bottom) and borazine signal (top). Inserted is the magnified hydrogen release signal in the range from 45 to 75 C. If the first step dehydrogenation is conducted at 80 C, Fe-doped AB doesn t yield any detectable borazine in the second step compared with neat AB. We investigated the final residue of the stoichiometric interaction between AB and FeCl 3 by using elemental analysis, XRD, IR, TPD, volumetric release etc. Although it is still difficult to determine (due to the amorphous nature of solid product), it is very likely that Cl - in FeCl 3 replaces H and bonds with B.

3 3. Sample foaming upon releasing H 2 Figure S3 Pictures of the neat (a), and Fe-doped (b) AB samples after heating them to 120 ºC. 4. NH 3 Concentration in the gaseous products Table S1 NH 3 concentrations of neat and Fe-doped AB after volumetric release at 80 ºC. Neat AB AB+5.0%FeCl 3 C NH3 460 ppm < 10 ppm 5. X-ray Diffraction and FTIR of the post-dehydrogenated AB samples Equiv. H % FeCl 3 -doped AB Time (h) Figure S4 Volumetric release measurement on 2.0 % FeCl 3 -doped AB at 60 ºC.

4 Intensity (a.u.) PAB PAB FeB d (Å) Figure S5 XRD patterns of the post-dehydrogenated neat AB (80 ºC) and 2.0 mol % Fe-doped AB samples (60 ºC). ( crystalline linear PAB) Transmittance (%) Wave number (cm -1 ) Figure S6 FTIR spectrum of post-dehydrogenated 2.0 mol % Fe-doped AB at 60 ºC (black) and neat at 80 ºC (blue). The FTIR spectrum of post-dehydrogenated Fe-doped AB is similar to crystalline CPB [S1,S2] and linear PAB [S3]. Due to the existence of FeB in the post-dehydrogenated sample, the low frequency region arises several new peaks. The broad peak around 3550 cm -1 at high frequency may belongs to the existence of amorphous PAB from self-decomposition of neat AB, or may be attributed to the O-H stretching contaminated by air during experiment Fe Mössbauer Investigations

5 a Relative Intensity (a.u.) b c d e alloy alloy alloy Fe 2+ f alloy Velocity mm s -1 Figure S7 Room temperature 57 Fe Mössbauer spectra of (a) metallic Fe, (b) FeCl 3, and (c) to (f) 5.0 mol % Fe-doped AB samples upon mixing at ambient temperature and dehydrogenating 0.2, 0.6 and 1.2 equiv. H 2 at 80 ºC. In the spectral analysis, the component of alloyed state iron was fitted by assuming a distribution in magnetic hyperfine fields, the other components was fitted by assuming Lorentzian lineshapes. As shown in Figure S7 the as-prepared sample mainly contains one ferrous quadrupole doublet and an alloyed component with a distribution in hyperfine magnetic fields, showing that the reduction of FeCl 3 by AB occurred upon mixing at ambient temperature. When the Fe-doped AB sample was heated to 80 C and released 0.2, 0.6 and 1.2 equiv. H 2, respectively, identical patterns with an average isomer shift around 0.19 mm s -1 relative to α-iron were observed, which is close to the isomer shifts of Fe 44 Co 19 B 37 and Fe 62 B 38 amorphous alloys (0.19 mm s -1 ) reported by Wonterghem et al. [S4].

6 Table S2 Room temperature 57 Fe Mössbauer parameters of 5.0 mol % Fe-doped AB samples dehydrogenated 0, 0.2, 0.6 and 1.2 equiv. H 2 at 80 ºC. For comparison, parameters of metallic Fe, pristine FeCl 2 and FeCl 3 are also listed. Composition Oxidation Spectral IS a QS b Magnetic Line-width d state of area (mm s -1 ) (mm s -1 ) field (T) (mm s -1 ) Fe (%) c metallic Fe FeCl 2 in Ar Fe FeCl 3 in Ar Fe AB+5%FeCl 3 Fe alloy AB+5%FeCl 3-0.2H 2 AB+5%FeCl 3-0.6H 2 alloy alloy AB+5%FeCl 3 alloy H 2 a IS, isomer shift, relative to α Fe at room temperature; b QS, electric quadrupole splitting; c relative resonance areas of the different components of the absorption patterns; d full linewidth at half maximum. 7. X-ray absorption Characterizations

7 Absorption (a.u.) Fe FeCl 3 AB+5% FeCl Energy (ev) Figure S8 Fe K-edge XANES spectra of metallic Fe, FeCl 3, and post-dehydrogenated 5.0 mol Fe-doped AB samples The XANES spectrum of the post-dehydrogenated FeCl 3 -doped AB resembles to that of metallic Fe, indicating the reduced chemical state of Fe in the post-dehydrogenated sample. FT(k 2 χ) (a.u.) Fe foil 5% FeCl 3 -AB fit Fe-B Fe-Fe R(Å) Figure S9 Fourier transform of Fe foil and post-dehydrogenated 5.0 % FeCl 3 -doped AB sample, the latter was fitted with Fe-B and Fe-Fe coordination. Phase shifts were not corrected Quantitative information of local structural parameters was obtained by fitting of the first peak in real space using the phase shift and backscattering amplitude extracted theoretical FeB compound. The single scattering paths of Fe-B and Fe-Fe were included in the fitting; the inelastic factor was fixed to 0.9. A reasonable fit of the first peak gives a Fe-B and Fe-Fe bond length of 2.12 and 2.50Å, respectively, which are close to the PDFs results.

8 8. Theoretical Investigations The simulation method was following the Bader charge analysis incorporated in Vienna Ab initio Simulation Package (VASP). Geometry optimizations of all stationary points and transition-state structures were calculated at the B3LYP / G(2d,p) level using the Gaussian03 package. The nature of the stationary points was determined with vibrational analysis at the same level. Single point energies were combined with zero-point energies, heat capacity corrections and T-S contributions to yield free energies at 298 K. Table S3 Simulation results of partial atomic charges borne by Fe and B in the crystals of FeB and Fe 2 B FeB Fe 2 B Fe B Fe B Electric Charge Table S4. Cartesian coordinates of the B3LYP/ G(2d,p) optimized geometries of all calculated structure BH 3 NH 3 (AB) FeB

9 FeB-AB FeB-AB TS FeB-AB TS

10 AB TS FeB-BH 2 NH BH 2 NH H

11 Table S5. Absolute energies (B3LYP/ G(2d,p)) of all calculated structures E (Hatree) H 0 (Hatree) H 298 (Hatree) G 298 (Hatree) BH 3 NH FeB FeB-BH 3 NH Fe-AB TS Fe-AB TS AB TS FeB-BH 2 NH BH 2 NH H E (kcal mol -1 ) H 0 (kcal mol -1 ) H 298 (kcal mol -1 ) G 298 (kcal mol -1 ) AB+FeB FeB-AB AB+FeB TS AB+FeB TS AB TS AB+FeB FeB-NH 2 BH 2 +H AB NH 2 BH 2 +H References: [S1] K. W. Böddeker, S. G. Shore, R. K. Bunting, J. Am. Chem. Soc. 1966, 88, [S2] [S3] A. Staubitz, A. P. Soto, I. Manners, Angew. Chem. Int. Ed.2008, 47, [S4] J. van Wonterghem, S. Morup, C. J. W. Koch, S. W. Charles, S. Wells, Nature 1986, 322,