核壳结构纳米多孔铂族催化剂的表面应变三维分布及其对氧还原催化的作用

The platinum-group core-shell structured nanoporous catalysts are highly active and durable for the oxygen reduction reaction (ORR) in proton-exchange membrane (PEM) fuel cells and metal-air batteries. Previous works have shown that the strain in the shell of a core-shell structured catalyst will either enhance or reduce its catalytic performance towards ORR, offering a tuning knob to further improve the catalytic performance. In this regard, the three-dimensional (3D) distribution of the strain in the platinum-group core-shell structured nanoporous catalysts and its effect on the ORR reaction is yet to be reported. The proposal aims to experimentally characterize the distribution of the tension strain and compress strain in nanoporous catalysts Au@Pt, Au@Pd, Cu@Pd and Cu@Pt via atomic-resolution imaging performed in an aberration-corrected transmission electron microscope. In addition, finite element method (FEM) will be employed to numerically expand the strain analysis to 3D to the above four nanoporous catalysts whose structure is obtainable via 3D electron tomography experiments. Furthermore, both the experimental and numerical characterizations will be correlated with catalytic performance measurements to elucidate the relationship between the 3D distribution of the surface strain and the catalytic properties.Then, the first principle calculation will be used to analyze and summarize the mechanism of the effects on the ORR catalytic performance of the 3D distribution of surface strain. The project will provide the strategy for optimize the catalytic performance towards ORR through turning the strain. The project will contribute to confirm the structure-performance relationship of nanoporous Pt group core-shell catalysts towards ORR, and will make a contribution for PEM fuel cells and metal-air batteries’ generalization.

核壳结构纳米多孔铂族催化剂对质子交换膜(PEM)燃料电池和金属-空气电池这两类清洁能源装置中的氧还原反应(ORR)催化具有高活性和高稳定性。研究表明，核壳结构催化剂表面的应变会显著影响ORR催化性能。然而，核壳结构纳米多孔铂族催化剂是具备多种表面曲率的三维多孔结构，其表面应变三维分布及其对ORR催化的作用尚未报道。申请人计划使用球差校正透射电镜的原子分辨成像和三维重构技术、结合晶格分析和有限元分析方法表征Au@Pt、Au@Pd、Cu@Pd、Cu@Pt纳米多孔催化剂表面应变三维分布，并测量其ORR催化性能，系统阐明所测性能与表面应变三维分布间的关系。进而结合第一性原理计算，分析总结表面应变三维分布对ORR催化性能的作用机制，为优化该类催化剂的ORR催化性能提供应变调控方案。本申请的实施将有助于确定核壳结构铂族催化剂的构效关系，有望为推广PEM燃料电池和金属-空气电池做出一定的贡献。

金属纳米多孔催化剂是具有复杂的双连续多孔结构、高比表面积，低密度的非负载型催化剂，广泛应用于CO氧化、甲烷裂解、氧辅助偶联等反应的催化。然而这种结构本征具有的表面应变会对催化性能产生影响。原子分辨的透射电镜技术可以表征这些应变。本报告应用透射电镜，研究了不同曲率下表面应变的分布，以及金属纳米材料在外场下应变的演变，具体成果为：1.通过球差校正透射电镜，获得纳米多孔Au不同曲率下应变的分布，并结合核壳结构的成分三维分布，获得核壳结构纳米多孔催化剂表面的应变分布统计分布；2.应用原位气相透射电镜，研究具有特殊暴露面的纳米多孔Au在催化甲烷热解时Au(111)晶面的变化；3.研究了Cu纳米颗粒中退火五重孪晶的形成及分解过程，阐明了其机理。在该项目的支持下，我们得到了一系列重要的研究成果，发表SCI学术论文3篇，完成了原定的科研计划，并做了一定的扩展工作。我们期望这些研究成果对推今后金属纳米催化剂的设计和研究起到一定的推动作用。