石墨烯包裹Pt纳米粒子用于燃料电池阳极的稳定性及其催化反应机理研究

Fuel cells can convert chemical energy directly into electrical energy with the characteristics of high efficiency, no emission of pollutants and simple structures, etc., which are considered to be one of the most important sources of energy in the 21st century. However, the poor stability of the Pt/C catalyst which is the core material of the anode hinders the commercial application of the fuel cells. This project intends to use graphene to encapsulate Pt nanoparticles to improve the stability of anode catalyst. On the one hand, the electrons of Pt can freely penetrate the graphene so as not to affect its catalytic performance due to the small number of layers of graphene used for encapsulating Pt nanoparticles; on the other hand, the outer graphene can effectively block the harsh reaction environment (such as strong acid, alkali and oxidant, etc.), to avoid the poisoning and corrosive consumption of Pt nanoparticles, so that the stability and life of anodic catalyst is improved greatly. In the current project, we plan to systematically investigate the influence of a series of factors such as the encapsulating degree, number of layers, element doping, surface curvature of the graphene and particle size, element doping of Pt nanoparticle on the surface electron modulation of the graphene and penetration degree of outer electron of Pt nanoparticle. Besides, the project explores the intrinsic relationship between the modulations of factors mentioned above and the activity and stability of the catalyst, which provides substantial theoretical basis for the preparing the anode catalyst of the fuel cell with high activity and stability.

燃料电池具有效率高、无污染、结构简单等优点，被认为是21世纪最重要的能源来源之一。然而，做为阳极核心材料的Pt/C催化剂因其稳定性较差，阻碍了燃料电池规模化应用。本项目拟用石墨烯对Pt纳米粒子进行包裹，来解决燃料电池阳极催化剂稳定性差的问题。一方面，由于包裹纳米Pt所用的是少层数石墨烯，Pt电子可以自由穿透石墨烯，从而不影响其催化性能的发挥；另一方面，纳米Pt外层包裹的石墨烯可以有效阻隔外界苛刻的反应环境（如强酸、强碱、强氧化剂等），避免纳米Pt的毒化和腐蚀性消耗，从而使催化剂的稳定性和使用寿命得到大幅提升。本项目拟系统地研究石墨烯的包裹程度、层数、掺杂、表面曲率以及Pt纳米粒子的尺寸、掺杂等因素对石墨烯表面电子的调变以及Pt粒子外层电子对石墨烯“穿透”程度的影响，探索石墨烯和Pt纳米粒子各项因素的调变与催化剂的活性及稳定性的内在关联，为制备高活性高稳定性的燃料电池阳极催化剂提供理论基础。

燃料电池是一种能够将燃料的化学能不经燃烧过程而直接转变成电能的装置，是未来最有发展前景的供电技术之一。碳负载Pt催化剂（Pt/C）是目前在燃料电池中应用最广泛的催化剂。为了满足实际应用中的功率需求，需要使用大量贵金属Pt来高效催化反应效率。此外，Pt催化剂易被燃料和空气中的CO等有毒气体毒化而失活。因此，降低贵金属Pt用量或提高Pt/C催化剂的抗毒性成为推动燃料电池发展的关键技术。.对于负载型催化剂而言，催化剂载体的结构或性质直接决定了其表面活性组分的分散性及金属载体的相互作用强度，从而影响催化剂的活性。本研究首先以石墨烯（GO）和碳纳米管（CNTs）为载体，制备了不同碳基载体负载Pt催化剂，并系统研究了载体对催化剂催化甲醇氧化性能的影响。结果表明，Pt在GO表面分散性优于CNTs，平均粒径仅为1.2 nm，因而Pt/GO表现出更加优异的甲醇氧化活性及稳定性。.为了便于催化剂微观形貌的观测，选用Pt/CNTs为基础催化剂，以乙腈为碳源，采用气相沉积法在Pt/CNTs表面包裹石墨烯，制备了Pt/CNTs@GO催化剂。对Pt/CNTs和Pt/CNTs@GO催化剂进行CO耐受性测试。与Pt/CNTs催化剂相比，Pt/CNTs@GO催化剂CO曲线的峰电位负向移动35 mV，表明Pt/CNTs@GO催化剂比Pt/CNTs催化剂具有更强的抗CO中毒能力，从而证实石墨烯包覆可有效提高Pt/C催化剂的抗CO中毒性能。.此外，本项目还制备了两种性能优异的甲醇氧化催化剂。利用聚苯胺热解制备了一种氮掺杂的碳载体，在其表面负载Pt纳米粒子，研究了不同碳化温度对催化剂结构及甲醇氧化性能的影响。结果表明，当碳化温度为900℃时，所制备的催化剂具有最优的催化性能，质量活性高达858 mA·mg-1·Pt，为商业Pt/C催化剂的2倍；利用一锅法制备了N掺杂多孔碳接枝碳纳米管的复合碳载体，并同过流电沉积发将Pt负载于其表面。结果表明，碳化温度为800℃所制备的催化剂具有最优甲醇氧化性能，其质量活性高达464 mA·mg-1·Pt。.