硼氢化钠碱性水溶液储氢体系微观结构的精细解析

Further progresses on the NaBH4 hydrogen storage, and the selection, design for hydrogen release catalyst and Direct Borohydride Fuel Cell (DBFC) were impeded by a hiatus due to lack of the acquaintance of the complex solution structure of the hydrogen storage borate solution NaBH4-NaOH-H2O system. In the present projects, solution structure of this systems will be researched systematically. Firstly, the predominant species distribution in this two systems will be given, through the Raman, IR, NMR and the structure sensitive physical chemistry properties (pH, density, viscosity etc.) and thermodynamics calculation. Secondly, the synchrotron radiation X-ray scattering will be applied two get the time-space-averaged structure, Fine resolution micro-structure of this system will be get through an Empirical Potential Structure Refinement (EPSR) which based on the Monte Carlo simulation. Then the CPMD and ab initio will be used to study the detailed micro-structure like the hydration, associate and “Dihydrogen Bond”. Comparative use those methods, a precise solution structure will be given, which may present some valuable guidance for understanding of the complex electrode mechanism, electrode kinetics of DBFC, and the transform rule between B-H and B-O bonds in aqueous solution. The research results may also provide some theoretical basis to design and explore a clean, efficient, and low cost chemical hydrogen storage system.

硼氢化钠碱性溶液储氢体系释氢催化剂及直接硼氢化燃料电池(DBFC)的选型和设计等有赖于对NaBH4-NaOH-H2O体系溶液微观结构的深入理解。针对这一问题，项目拟首先通过Raman、IR、NMR及溶液敏感性质的测量并结合热力学计算给出在这个体系中硼的存在形态；利用同步辐射X射线散射法给出在溶液的时间空间平均结构，并利用结构参数计算和基于Monte Carlo的经验势结构精修(EPSR)实现对结构参数的精细化解析；项目还将通过从头算分子动力学模拟（CPMD）和量子化学从头算（ab initio）研究深入探讨溶液中存在的水合、缔合尤其是溶液中的 “二氢键”等结构细节。研究有望获得更准确、更精细的溶液结构信息，深入理解NaBH4碱性溶液的储氢储能的微观结构化学本质及B-H键与B-O键的转化规律，为该体系化学释氢催化剂和DBFC的设计和选型等提供理论基础。

硼氢化钠碱性溶液储氢体系释氢催化剂及直接硼氢化燃料电池(DBFC)的选型和设计等有赖于对NaBH4-NaOH-H2O及NaB(OH)4-H2O体系溶液微观结构的深入理解。针对这一问题，项目通过Raman，IR光谱确定这个体系中硼的存在形态。利用同步辐射X射线散射法给出在溶液的时间-空间平均结构，利用结构参数计算和基于Monte Carlo的经验势结构精修(EPSR)实现对结构参数的精细化解析。.研究发现，在硼氢化钠溶液中，BH4-与约6.0±1.6个水分子之间通过二氢键发生水合，“二氢键”的形成既是溶液稳定的原因也是硼氢化钠水解的关键因素。BH4-与Na+通过四面体共顶点和四面体共边的形式形成接触离子对，其中四面体共边的接触离子对更为稳定，为溶液中主要的离子缔合形态，这种缔合形式也遗传到了他们的晶体（NaBH4.2H2O）中。.X射线散射(X-Ray Scarttering, XRS)是研究溶液结构的有效手段。该方法可直接测量溶液中原子-原子(site-site)间的分布函数，相对于XAFS而言其对长程相互作用也更为敏感。EPSR采用Monte Carlo的方法来不断减小模拟结构产生的结构函数(F^sim (Q))与实验的结构函数(F^exp (Q))之间的差值来实现液态结构的精修。借助 X射线散射和EPSR可实现液态（非晶态）的精细化结构解析，该方法对一些难处理的低散射复杂样品也表现出了相当的适用性。

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