燃料电池纳米催化剂的稳定化

低温燃料电池是理想的移动式电源,它所采用的电催化剂主要为Pt基贵金属纳米催化剂。提高纳米催化剂在电池内部环境中的稳定性、抑制其活性衰减,对于延长低温燃料电池的使用寿命和节约成本具有十分重要的意义。本文从三个方面综述了近年来在低温燃料电池纳米催化剂稳定化方面的研究进展。首先,通过载体效应实现催化剂的稳定化,包括碳载体的石墨化、碳载体的掺杂、表面功能化及其他载体的采用等。其次,通过空间效应实现催化剂的稳定化,包括催化剂粒子表面覆盖、催化剂粒子微孔嵌入、催化剂表面杂多酸单层自组装及聚合物电解质空间阻隔等。再其次,通过协同效应实现催化剂的稳定化,包括提升金属粒子的氧化电位、强化组分间的相互作用等。最后,对低温燃料电池纳米催化剂稳定化的发展前景进行了展望。

Stabilization of Nanocatalysts in Fuel Cells

Low temperature fuel cells are considered to be promising portable power sources.Pt based noble metal nanocatalysts are widely used as electrocatalysts in low temperature fuel cells.The electrochemical stability of nanocatalysts is of significance for long-term operations of fuel cells.Unfortunately,Pt based nanocatalysts are unstable in fuel cells and tend to lose their activities gradually during long-term discharge processes.The activity losses of nanocatalysts are normally caused by nanoparticle agglomeration,metal dissolution,poisoning,support corrosion,etc.In order to extend the lifetime of fuel cells and save costs,the stability of nanocatalysts under internal environments of fuel cells should be improved.Recently,studies regarding the stabilization of Pt based nanocatalysts attracted much attention and various methods were developed to prevent the degradation of nanocatalysts.In this paper,recent research works about the stabilization of nanocatalysts in low temperature fuel cells are reviewed.Firstly,nanocatalysts are stabilized by support modifications,which include the graphitization of carbon supports,the doping of carbon supports,the surface functionalization of carbon supports and the use of other supports.Secondly,nanocatalysts are stabilized by steric effects,which are related to the surface covering of catalyst nanoparticles,the micro-pore enveloping of catalyst particles,the monolayer self-assembly of polyoxometallate on the catalyst surface and the steric obstruction of catalyst nanoparticles by polymer electrolytes.Thirdly,nanocatalysts are stabilized by synergetic effects,such as the elevation of metal oxidation potentials and the enhancement of the interaction between catalyst components.Finally,an outlook of the future development of the stabilization of nanocatalysts in low temperature fuel cells is provided.