Experimental Evidence of Na2[B12H12] and Na Formation in the Desorption Pathway of the 2NaBH4+ MgH2System (original) (raw)

We report in the present work the desorption pathway of the 2NaBH 4 + MgH 2 system. Measurements on samples heat treated up to 450 °C for different times have been performed by ex-situ X-ray powder diffraction (XRPD) and solid state magic angle spinning (MAS) nuclear magnetic resonance (NMR). Ex-situ X-ray powder diffraction experiments conducted on full desorbed samples allowed to identify nanocrystalline MgB 2 and metallic Na as dehydrogenation products. 11 B and 23 Na NMR analyses have been also carried out in order to evaluate the structural evolution of decomposed materials. Our measurements show that the local structure of MgB 2 was influenced by the replace of Mg with Na atoms in the Mg sites. Moreover, amorphous Na 2 [B 12 H 12 ] was detected in the partially desorbed sample and in the final products of the decomposition reaction. The presence of the [B 12 H 12 ] 2-anion was confirmed by both direct comparison with the 11 B{ 1 H} NMR spectrum of pure Na 2 [B 12 H 12 ] and dynamic Cross Polarization experiments.