高稳定纳米纤维负载型Co-B催化剂的制备及在硼氢化物液相释氢中的机理研究

Transition metal boride amorphous catalysts represented by Co-B show a good prospect of application in catalytic hydrogen production from borohydride hydrolysis. However, the catalytic activities of CoB catalyst can decay gradually with time during operation, and its catalytic activity obviously declines after several recycles which become the main bottleneck of this kind of catalyst for widespread application. .Transition metal boride amorphous catalysts represented by Co-B show a good prospect of application in catalytic hydrogen production from borohydride hydrolysis. However, the catalytic activities of CoB catalyst can decay gradually with time during operation, and its catalytic activity obviously declines after several recycles which become the main bottleneck of this kind of catalyst for widespread application. .In this project, a novel method of stabilizing Co-B catalyst by conducting polymeric nanofibers is proposed. This method offers the advantages of high specific surface areas and monolithic feature of polymeric nanofiber support. By adjusting the microstructure of polymeric nanofibers and confined transformation of cobalt ions, it is expected to improve the dispersing stability of Co-B. Meanwhile, the deposition adsorption of by-products onto Co-B is expected to be inhibited based on the electron coupling and steric hindrance of polymeric nanofiber matrix to Co-B amorphous particles..This project will focus on the study of the following fundamental issues in Co-B stability: 1) The dispersion and stabilizing effect of conducting polymer media on cobalt-contained precursor; 2) The preparation of cobalt-containing porous conducting nanofiber with high specific surface area; 3)The dispersion and electron coupling effect of Co-B in polymeric nanofiber matrix; 4) The diffusion and surface reaction kinetic study of reactant and product molecules in conducting nanofiber-supported Co-B catalyst. .This research is attempted to conduct basic scientific research for illuminating the mechanism of Co-B microscopic deactivation. Furthermore, it is expected to offer a novel method and idea for improving the stability of cobalt boride-type amorphous catalysts.

以Co-B为代表的过渡金属硼化物非晶催化剂在硼氢化物液相制氢等领域具有广泛应用前景，但其催化活性会随时间逐步衰减，几个循环之后催化活性明显下降，成为该类催化剂推广应用的主要瓶颈。.本项目提出导电高分子纳米纤维稳定Co-B非晶粒子的创新方法，该方法耦合高分子纳米纤维高比表面积与整体特性，通过调控纳米纤维多孔微观形貌和钴离子的限域转化，提高Co-B粒子的分散稳定性。同时基于导电纳米纤维载体对Co-B非晶粒子的电子耦合和空间位阻保护效应，抑制副产物沉积吸附。.本课题拟展开以下内容研究：1) 导电高分子介质对钴前驱体的分散稳定作用; 2)含钴高比表面导电纳米纤维的制备; 3) 硼化钴在纳米纤维中的分散与电子耦合效应；4) 反应物产物分子在导电纳米纤维负载催化剂中的扩散与表面反应动力学。.本研究将为阐明Co-B的微观失活机制进行基础科学研究，并能为提高Co-B非晶催化剂的稳定性提供一种方法和思路。

氢气以其较高的能量密度和环境友好特性被视为下一代绿色能源，而氢气的储存和运输是氢能经济发展的关键。相对于高压低温的物理储氢方式，安全高效的化学储氢技术更具应用前景。在诸多化学储氢材料中，NaBH4以其较高的能量密度和环保优势备受瞩目。虽然低成本过渡金属CoB催化剂在NaBH4碱性储氢液水解释氢中展现了良好的催化活性，但是CoB的催化活性会随时间逐步衰减，稳定性不足成为制约CoB催化剂推广的瓶颈。针对CoB极易团聚的本质特性，本研究旨在利用导电高分子纤维及其衍生物作为催化剂载体提高CoB活性组分的分散度和固载稳定性。为了提高CoB的分散度，本课题通过聚苯乙烯（PS）纳米纤维模板和浸渍法制备了导电高分子聚苯胺（PANI）中孔纤维支撑的CoB催化剂，研究表明磁性CoB活性组分可高度分散于PANI中空纤维的内腔，显著提高了CoB的分散度和固载强度，抑制了过去使用过程中CoB极易与催化剂载体分离的劣势。释氢实验表明PANI中孔纤维支撑的CoB催化剂展示了良好的催化剂活性（2300ml. min-1. g-1）和明显提高的循环稳定性。基于高分子纤维限域分散CoB的思路，本项目进一步拓展开发了基于高分子聚丙腈（PAN）静电纺丝纤维衍生制备的PAN碳纤维负载CoB催化剂，通过一种原创性预还原和后碳化相结合工艺显著提高了CoB活性组分在PAN碳纤维基体中的分散度，TEM和SEM表征表明单分散CoB纳米颗粒高度分散于整个PAN碳纤维体相，CoB粒径减小至大约10~30nm，分散度远高于与没有预还原处理的Co/PAN碳纤维催化剂。通过高分辨TEM衍射可以证明PAN碳纤维基质中的CoB呈现非晶态结构，而Co/PAN碳纤维中钴物种却呈现了明显的结晶相。 CoB/PAN碳纤维催化剂在NaBH4水解释氢中也呈现了良好的催化活性和稳定性，其释氢活化能大约为47.7kJ.mol-1。