Synthesis of amorphous manganese borohydride in the (NaBH4-MnCl2) system, its hydrogen generation properties and crystalline transformation during solvent extraction

• 来源期刊: 能源化学
• 年，卷（期）: 2017,（1）
• 页码范围: 24-34
• 页数: 11页
• 语种: 英文

摘要

The mixture of (2NaBH4 + MnCl2) was ball milled in a magneto-mill.No gas release was detected.The XRD patterns of the ball milled mixture exhibit only the Bragg diffraction peaks of the NaCl-type salt which on the basis of the present X-ray diffraction results and the literature is likely to be a solid solu tion Na(Cl)x(BH4)(1-x),possessing a cubic NaCl-type crystalline structure.No presence of any crystalline hydride was detected by powder X-ray diffraction which clearly shows that NaBH4 in the initial mixture must have reacted with MnCl2 forming a NaCl-type by-product and another hydride that does not exhibit X-ray Bragg diffraction peaks.Mass spectrometry (MS) of gas released from the ball milled mixture during combined MS/thermogravimetric analysis (TGA)/differential scanning calorimetry (DSC) experiments,confirms mainly hydrogen (H2) with a small quantity of diborane gas,B2H6.The Fourier transform infra-red (FT-IR) spectrum of the ball milled (2NaBH4 + MnCl2) is quite similar to the FT-IR spectrum of crystalline manganese borohydride,c-Mn(BH4)2,synthesized by ball milling,which strongly suggests that the amorphous hydride mechano-chemically synthesized during ball milling could be an amorphous manganese borohydride.Remarkably,the process of solvent filtration and extraction at 42 ℃,resulted in the transformation of mechano-chemically synthesized amorphous manganese borohydride to a nanostructured,crystalline,c-Mn(BH4)2 hydride.