硼氢化物储氢材料的光催化吸放氢设计及其作用机理

Storing hydrogen in a safe, efficient manner is the key to the widespread use of hydrogen energy at present. Borohydrides are considered as one of the most promising hydrogen storage materials and receive a lot of attention due to their high hydrogen storage capacities. However, two significant problems, high hydrogen desorption/absorption temperatures and low reversibility, prevent borohydride-based hydrogen storage materials from practical applications. In this project, based on the traditional thermochemistry of internal energy-chemical energy transformations, photocatalysis of luminous energy-chemical energy transformations is introduced to tailor the hydrogen desorption/absorption thermodynamics and kinetics of borohydride-based hydrogen storage materials, and subsequently to lower the operating temperatures and improve reversibility. First, tailoring the oxidation (Eo) and reduction (Er) potentials of the borohydrides by the composition of borohydrides, and tailoring the potentials of conduction band electrons (Ecb) and valence band holes (Evb) by the change of photocatalysts. Then the photocatalysis-coupling (Er > Ecb，Eo > Evb) borohydride-based hydrogen storage materials are obtained by using the appropriate medium and method. Second, clarifying the hydrogen desorption/absorption mechanism of the as-prepared hydrogen storage materials by the comparative investigations on the hydrogen desorption/absorption thermodynamics, kinetics, structural changes and compositional changes under thermochemistry and photocatalysis conditions.

氢气的安全、高效储存是目前发展大规模氢能应用的关键。硼氢化物具有极高的储氢密度，被认为是最有应用前景的储氢材料之一，受到了广泛的关注。但是，目前硼氢化物储氢材料仍存在吸放氢温度高和可逆性差两大问题，和实用化要求还有一定差距。本项目拟在传统内能-化学能转化的热化学基础上，再引入光能-化学能转化的光催化，以实现对硼氢化物储氢材料吸放氢热力学和动力学的调控，降低其吸放氢温度并改善可逆性。首先通过反应物复合调控硼氢化物的吸放氢氧化（Eo）还原（Er）电位，通过物相改变调控光触媒的光生电子（Ecb）空穴（Evb）电位，辅以适合的介质和制备方法，得到光催化耦合（Er > Ecb，Eo > Evb）的硼氢化物储氢材料。然后通过对比研究制得储氢材料在热化学、光催化条件下的吸放氢热力学、动力学性能和结构、成分变化，阐明其光催化吸放氢机理。最终获得吸放氢性能更加接近实用化需求的硼氢化物储氢材料。

本项目针对硼氢化物储氢材料的吸放氢温度高这一关键问题，在传统基于内能-化学能转化的热化学基础上，再引入光能-化学能转化的光催化，实现了对硼氢化物储氢材料吸放氢热力学和动力学的调控，降低了其吸放氢温度。经细致调研，结合第一性原理计算，本项目设计并制备了多种理论上符合光催化要求的硼氢化物与光触媒组合，并随后进行了实验验证。开发了碱金属硼氢化物-二氧化钛的光催化水解体系和氨硼烷-碱金属氢化物-二氧化钛光催化储氢体系，以上体系都会在光催化作用下显示出更优的吸放氢性能。同时，本项目从综述动力学模型的发展入手，经适当的优化和解析化处理，得到具有较好普适性的、能够更加深入解析反应机理的动力学模型，并成功将其用于不同种类的储氢材料中。优化了适用于几何收缩模式的Chou模型和适用于形核长大模式的JMAK模型，并开发了一套联立分析储氢材料等温和变温动力学数据的方法。本项目已发表SCI论文15篇，申报国家发明专利1项，培养博士生2人，硕士生2人。