高分子胺功能化三维结构Pd基金属纳米晶的氧还原性能研究

The electrocatalytic oxygen reduction reaction (ORR) is one of the key reactions in direct alcohol fuel cells. In general, three-dimensionally (3D) interconnected noble metal nanostructures exhibit superior electrocatalytic activity and durability towards the ORR because of their attractive structural features, such as porosity, high surface area, interconnected nanostructure, excellent electrical connectivity, and high density of twinned defects. Traditionally, ORR improvement mainly focus on the design and manipulation of the composition, particle size and shape of noble metal nanostructures. Very recently, a new trend in electrocatalyst designs has been proposed, which is based on the modification of the metal surface by nonmetallic molecules that can block the adsorption of poisoning species and spectator anions. In the project, we report a convenient wet chemical method to synthesize the polymeric amine (PMA) functionalized 3D Pd-based nanostructures with controlled morphology, size and composition. In the process, the influence of experimental parameters (such as the reaction temperature, reaction time, solution pH and molecular structure, etc.) on the size, morphology and composition of Pd-based nanostructures will be investigated systemically. Furthermore, the electrocatalytic activity, durability and alcohol tolerant ability of PMA functionalized 3D Pd-based nanostructures towards the ORR will be explored by using various electrochemical techniques. In addition, the effect of PMA layer adsorbed on 3D Pd-based nanostructures surface on electrocatalytic activity, stability and alcohol tolerant ability of 3D Pd-based nanostructures also will be demonstrated detailedly by analyzing experimental data. In summary, the implementation of the project will favor the fundamental research of 3D Pd-based nanostructures synthesis and the development of new electrocatalyst designs.

氧还原反应(ORR)是直接醇类燃料电池中重要反应之一。三维结构贵金属纳米晶对ORR呈现出高的电催化活性和稳定性。传统上，ORR活性改进研究主要集中在调控贵金属纳米晶的尺寸、形貌和化学组成。近来，通过贵金属纳米粒子表面化学功能化来改进其电催化性能成为一个全新的电催化剂设计理念。本项目拟在高分子胺类化合物(PMA)体系中合成具有各种形貌、尺寸和组成的PMA功能化三维结构Pd基金属纳米晶。揭示溶液pH、反应温度、还原剂类型、PMA分子构型等实验参数对产物形貌、结构、尺寸、组成的影响，深入掌握PMA在Pd基金属纳米晶合成过程的功能及作用机制。利用电化学技术研究PMA功能化Pd基金属纳米晶对ORR的电催化性能。结合光谱数据研究Pd基金属纳米晶表面PMA吸附层改进电催化活性、稳定性和耐醇性的关键机理。本项目对于Pd基金属纳米晶合成基础研究、发展新的电催化设计理念等方面具有很好的理论和实践意义。

目前，阴极氧还原（ORR）动力学迟缓、催化剂稳定性差、醇渗透等问题限制直接醇类燃料电池的商业化进程。本项目拟在高分子胺类化合物(PMA)水溶液中合成各种PMA功能化三维结构贵金属纳米结构物，系统研究其在PMA存在条件下的生长机理，调查其ORR活性、稳定性和耐醇性。目前，我们已成功合成出多种PMA功能化三维结构贵金属纳米晶，证实PMA络合-还原法是一种有效调控贵金属纳米晶形貌且同步实现表面功能化的有效方法。在合成过程中，PMA可充当络合剂、稳定剂、模板剂和表面修饰剂。电化学实验结果显示三维结构贵金属纳米晶高度分枝的三维结构可有效抑制奥斯特瓦尔德熟化，改进电催化剂的稳定性。利用有机高分子PMA修饰贵金属纳米晶表面，借助于N-金属键可强烈影响贵金属纳米晶电子结构，调控ORR活性。PMA分子中–NH2官能团质子化可显著提高贵金属纳米晶表面质子浓度，从而提高ORR动力学。特别地，贵金属表面的PMA层可充当“分子窗纱”有效地阻止体积较大的醇分子通过，而允许体积较小的氧气分子通过，从而显示出良好的ORR选择性。实验结果显示贵金属纳米晶表面化学功能化可改变电极/电解液界面性质，进而改变贵金属纳米晶电催化活性和选择性，这对于发展新的ORR催化剂设计理念方面具有很好的理论意义。