强磁场作用下Pt纳米颗粒组织演化及其催化性能研究

Metallic platinum is the first choice of catalyst material for low temperature fuel cell. The improvement of specific surface area of Pt nanoparticles and utilization of structure sensitivity of Pt crystal surfaces is significant important for promoting the catalytic properties. The process of ion transport, electron transfer, chemical reaction and crystal growth during electroless deposition could be non-contacting controlled by the Lorentz force and magnetization force of high magnetic field. It is proposed that Pt nanoparticles are fabricated on carbon fiber paper under high magnetic field by electroless deposition in this project, which is initiated by galvanic process and the specific surface area of Pt particles could be improved; preferred orientation of Pt grains could be induced under the influence of high magnetic field and the catalytic properties is enhanced finally. It is studied the influence of high magnetic field on the shape, grain diameter, dispersion and orientation of Pt nanoparticles; it is revealed the mechanism of microstructure evolution of Pt nanoparticles affected by high magnetic field; it is explored the electrocatalytic activities and electrochemical stability of Pt nanoparticles on hydrogen oxidation and oxygen reduction; it is illustrated the relationship between specific surface area, preferred orientation and catalytic activities; it is clearly indicated the mechanism of controlling catalytic properties of Pt nanoparticles by microstructure evolution under high magnetic field; it is proposed the prototypes of fabricating Pt nanoparticles with excellent catalytic activity by high magnetic field. This work has significant value on basic and applied research of promoting fuel cells as a new type of energy.

金属Pt是低温燃料电池首选的催化剂材料，提高Pt颗粒的比表面积和利用Pt晶面的结构敏感性对提高其催化性能具有重要意义。强磁场通过洛伦兹力和磁化力可以无接触地控制化学镀的离子输运、电子转移、化学反应和晶体生长过程。本项目提出在原电池反应触发化学镀制备Pt纳米颗粒的过程中施加强磁场，利用上述强磁场的作用效果，提高Pt颗粒的比表面积，诱发Pt晶粒的择优取向，进而提高其催化性能。研究强磁场对Pt纳米颗粒的形状、粒径、分散度和晶体取向的影响规律；揭示强磁场对Pt纳米颗粒组织演化的作用机理；考察Pt纳米颗粒对氢的氧化和氧的还原反应的电催化活性和电化学稳定性；阐明比表面积、择优取向等结构与催化活性的关系；明确强磁场通过Pt纳米颗粒微观组织调控催化性能的机理；提出利用强磁场制备具有高催化活性的Pt纳米颗粒的技术原型。研究成果对推进燃料电池作为新型能源的基础和应用研究具有重要价值。

燃料电池作为一种新型绿色能源，具有能量转换效率高，燃料多样化、噪音低、对环境污染小等优点，受到越来越多的关注。目前，催化剂作为其关键材料主要采用的仍是铂基催化剂，但是铂金属的价格昂贵，使其应用受到了限制，为了降低燃料电池的成本，以Pt为基础掺入其他金属元素制成合金催化剂受到了广泛研究。本课题组采用强磁场制备Pt系纳米合金颗粒。在强磁场条件下采用原电池反应触发化学镀制备Pt-Fe纳米合金颗粒，并对其催化活性进行考察，分析了Pt-Fe纳米合金颗粒在强磁场下的组织演变与催化性能的内在联系；另外，在强磁场条件下采用原电池反应制备不同Pt壳层厚度的Pt-Ni@Pt合金催化剂，研究了强磁场对Pt壳层结构和Pt-Ni@Pt合金催化剂催化性能的影响，提出利用强磁场制备具有高催化活性的Pt系纳米合金颗粒的技术原型。