纳米Pd基合金/氮硫共掺杂有序介孔碳的设计合成及其电催化性能与界面结构研究

Rechargeable lithium-air batteries have recently received much attention due to their great potential for achieving super-high specific energy density, which have a wide application in the field of future electric vehicles (EVs). But the low electrode reaction efficiency and high overpotential have serious impacted its energy efficiency and cycle performance. All the problems have focused on how to design a high efficient and stable nano electrocatalyst. In this project, liquid acrylonitrile telomere with sulfur will be prepared in non-solvent system by firstly suggested. Nitrogen/sulfur co-doped ordered mesoporous carbon will be synthesized by template method and applied as supports for Pd/transition metal elements alloy nanoparticles. The as-prepared products will be employed as electrocatalysts for the cathode reactions. It is expected to increase the catalytic activity and stability while decrease the amount of noble metals, therefore, increase the performance and life time for the lithium-air batteries. The behaviors of interfacial interaction between alloy catalyst and nitrogen/sulfur co-doped ordered mesoporous carbon, influence rules between the structure of the nano electric catalyst (bulk, surface and defect) and catalytic performance, and the synergistic effect, structure-activity relationship and catalytic mechanism between the components of alloy catalyst will be studied by first principle simulation , HRTEM、XRD、XPS、SEM and electrochemical testing technology. Some significant conclusions for guiding nano electric catalyst design and optimization will be obtained. The aim of the project is to realize the controllable synthesis of materials and develop a kind of new nano palladium- transition metal alloy electrocatalysts with excellent property for non-aqueous lithium-air batteries.

锂空气电池在实现超高能量密度方面有巨大的潜力，在电动汽车等新能源领域有广阔的应用前景，但其电极反应效率低、电极过电势高等缺点严重影响了其能量效率和循环性能。设计出高效稳定的电催化剂是解决以上问题的关键。本项目创新性提出在无溶剂体系中合成含硫的液态丙烯腈调聚物，采用模板法制备出氮硫共掺杂有序介孔碳，用以担载通过计算机辅助设计合成的单分散纳米Pd/过渡金属元素合金催化剂，探索在降低贵金属用量的情况下，增强其催化活性和稳定性的新方法。利用第一性原理的计算模拟并结合TEM、XRD、XPS及电化学测试技术，研究纳米合金催化剂与氮硫共掺杂介孔碳界面之间的作用行为，阐明纳米电催化剂的结构（体相、表面及缺陷）改变对催化性能的影响规律，揭示合金催化剂组分间的协同效应、构效关系及催化机理，以理论指导纳米催化剂微观结构与催化性能调控、设计和优化，为最终开发出高活性和高稳定性的锂空电池催化剂提供科学依据和技术支持

本项目利用第一性原理的计算模拟并结合TEM、XRD、XPS及电化学测试技术,采用自由基调聚法成功设计合成了含硫元素的液态丙烯腈低聚物碳（ANT），以其为前驱体，通过模板法制备出氮硫共掺杂多孔碳（NS/C），并以此为基底负载二元PdNi以及三元Pd-M纳米合金以构筑高效且低载量的贵金属锂空气电池催化剂，阐明了掺杂元素（N，S）与Pd-M合金电催化剂活性组分间的相互作用规律和催化机理，从微观、宏观等层次上充分认识纳米结构和复合结构对Pd基合金催化剂在充放电过程中的影响机制。为进一步研究纳米Pd-M合金电催化剂的结构与催化活性的关系，阐明纳米Pd基合金电催化剂的成分、尺寸、载量等参数对催化性能的影响以及过渡金属元素M(M=Cu, W or Ni)对贵金属Pd催化活性的协同效应，本项目也通过化学还原法制备PdNiSn纳米三元合金担载在氮掺杂石墨烯上，以及采用溶剂热方法制备了Pd/NG, PdSn/NG, PdCo/NG和PdSnCo/NG复合纳米催化剂。其中将PdNi-NSMmC/CP直接用做锂空气电池电极时，电池在过电位、容量、倍率、循环等性能方面有显著的提升。电流密度为300mA g-1，限制容量为500mAh g-1和1000mAh g-1时，电池的循环圈数分别能达到120圈和70圈。电流密度为300mA g-1，充放电截至电压分别为4.5V和2.0V时，电池放电比容量达到9965mAh g-1，充放电过电势为1.05V，即使电流密度增大至1400mA g-1时，电池仍有4412mAh g-1的比容量。此外，通过第一性原理，基于PdCu的二元及三元合金体系构筑催化剂模型进行DFT模拟，通过对比吸附能，确定了表面和ORR中间体最稳定的吸附构型；通过对热力学和动力学性质计算和分析，确定了最佳反应途径，为将来开发出低成本，高活性和高稳定性的锂空电池催化剂提供科学依据和技术支持。