多元多相高容量轻金属氢化物的结构、形貌及轻质高效催化剂的设计和材料储氢机理研究

Light-metal hydrides which possess high hydrogen storage density are a type of highly potential hydrogen storage materials of fuel cells for vehicles. However, the shortcomings of comparatively high de-/hydrogenation temperatures, rigorous reversibility or/and low reaction kinetics prevent them from ever-expanding applications. Their overall hydrogen storage properties are greatly desired for remarkable improvement and the mechanisms of the improvement on the hydrogen storage properties need to be further clarified. In the present proposal, the high-capacity lithium hydrides and light-metal borohydrides are proposed to be objective hydrogen storage materials. Investigations will be developed in terms of exploring novel light-weight carbonaceous catalyst and its composites with other catalysts; designing and synthesizing new-type dual-cation metal borohydrides; constructing multicomponent and multiphase high hydrogen composites of high capacity; synthesizing nano-scaled hydrogen storage materials of different morphologies and sizes assisted with hollow carbonaceous nano-frameworks, in aims to achieve a type of novel hydrogen storage materials of high hydrogen storage density, favorable hydrogen storage thermodynamics and kinetics, and high cycling stability. Effects of the composition, structure, morphology, size issue, catalyst on the hydrogen storage properties of the materials are going to be systematically investigated and the regulations are proposed to be revealed. Key effects and mechanisms which influence the de-/hydrogenation properties of the target materials are expected to be clarified. The developed hydrogen storage materials and high activity catalysts, their fabrication technology, the mechanism and theories of the de-/hydrogenation processes, which are desiredly achieved in proposal, are hopefully able to provide novel approaches and theories for the further investigation and development of hydrogen storage materials of high performance.

高容量轻金属氢化物是一类极具潜力的车载燃料电池氢源材料，但其存在或吸放氢温度高，可逆条件苛刻，或动力学性能差,或兼而有之等缺点，目前尚未得到规模应用，其综合储氢性能亟待提高，相关储氢性能改善机理有待进一步明确。本项目拟以高容量锂氢化物和轻金属硼氢化物为主要研究对象，通过探索研究新型轻质碳质及其复合催化剂、设计合成高性能双金属阳离子硼氢化物、构建多元多相高容量氢化物复合体系和采用中空碳基纳米框架辅助合成多形貌多尺度纳米储氢材料等多种方法，致力于获得兼具高容量、良好的吸放氢热力学、动力学及可逆性的新一类储氢材料体系。系统研究体系的成分、相组成、结构形貌及尺寸和催化相对材料储氢性能的影响，阐明其影响规律，揭示影响材料吸放氢性能的关键因素及其作用机理。项目研究获得的材料及其高效催化剂、材料制备技术、相关吸放氢过程和储氢性能提高机理可望为高容量储氢材料的进一步研究和开发提供重要的实践方法和理论依据。

轻金属硼氢化物储氢容量高，是一类极具潜力的车载燃料电池氢源材料，其中LiBH4具有高达18.5 wt%的理论储氢容量，但其吸放氢温度高，可逆条件苛刻，阻碍了其实际应用。项目以LiBH4为主要研究对象，通过特殊结构的多孔碳材料纳米限域、多相多元结构复合、高效催化相的设计和原位合成引入等方法，显著提高了LiBH4基储氢材料的性能。通过催化、纳米限域和材料表面界面的作用，优化了体系的吸放氢反应路径，显著提高了LiBH4等体系的储氢性能，揭示了性能提高机理。通过项目实施，获得了多个基于LiBH4的高性能储氢材料新体系。获得的一种超细纳米Li3BO3和NbH双相催化剂原位引入的LiBH4体系的起始放氢温度低至190 °C，比商业LiBH4降低了近200 °C，在400 °C下放氢7.9 wt%，双相催化剂的协同催化降低了体系的放氢表观活化能，体系表现出优良的吸放氢循环性能，经30次吸放氢循环后，容量保持率仍高达91%，容量保持有7.2 wt%，获得了目前LiBH4基储氢材料最好的循环性能；设计合成了负载有不同纳米催化相的高孔隙率一维多孔无定型碳和纳米碳管双相碳复合材料，其作为纳米限域载体，在催化、纳米限域和高热导率纳米碳管的协同作用下，负载LiBH4高达60 wt%的体系显示出高吸放氢可逆性，峰值放氢温度低至318 °C，较单一LiBH4降低了117 °C，在加热到350 °C的过程中就能放出约7 wt% H2，320 °C下的二次等温放氢量达6.8 wt%；获得的一种高比表面积和高空隙率的纳米中空多孔球形碳，在无金属催化剂的条件下，负载70 wt%LiBH4的体系的放氢温度低至200 °C，在350°C保温25分钟可放出7.8 wt％H2，是目前文献报导的具有最高LiBH4负载量纳米限域体系。获得了在高效催化相和纳米限域作用下，LiBH4体系放氢产物在吸氢过程中高热力学稳定性吸氢中间相Li2B12H12生成量的减少可显著提高其吸放氢性能这一普遍规律，为LiBH4体系进一步吸放氢性能的提高提供了理论指导。项目研究结果对于进一步开展高性能硼氢化物储氢材料的研究，促进其实用化具有重要的实践和理论指导意义