Pd基有序金属间化合物用于碱性膜燃料电池氢氧化反应电催化

Exploring highly active, stable and relative low-cost catalysts for the hydrogen oxidation reaction (HOR) is of vital importance for developing alkaline polymer exchange membrane fuel cells (AEMFC). This project is aiming to reveal the structure-activity relationship of the nanomaterials by comparing the discrepant catalytic performance among the tunable structure of the Pd-based catalysts. In terms of the hydrogen storage behavior of Pd-based nanomaterials as the springboard，we succeeded in controlling the transformation from disordered alloy phase to ordered intermetallic phase by introducing 3d transition metals and adjusting the parameters of the reaction. Above methods may effectively reduce the hydrogen binding energy of the catalysts, optimize the interaction of the ligands, and finally constructs the relationships between hydrogen storage behavior and the catalysts activities, which would enhance the HOR activities expectedly. Moreover, the durability and activity could be further improved by forming a Pt shell on the Pd-based nanocatalysts core with a spontaneous substitution method. These improvements were attributed to ligand effect and compressive strain effect originating from the interaction of the core-shell structure. By exploring the performance of the serial catalysts, the catalytic mechanism could be comprehended definitely and used as the guidance for designing the catalysts. By analyzing the differences between surface-structure and the activity using in-situ TEM and synchrotron radiation technique, the catalytic mechanism would be revealed and then guiding the optimal design of the catalysts. The strategy of constructing ordered Pd-based core and Pt-shell structure provides a new direction for catalyst optimization and could be applied for the AEMFC as a promising candidate.

开发低成本、高活性和稳定的氢电极催化材料对于发展碱性膜燃料电池具有重要意义。本项目旨在通过理性设计，可控构筑Pd基纳米电催化剂，调控碱性氢氧化电催化性能。通过引入3d过渡金属元素以及调节反应参数，实现单金属Pd从无序的合金相到有序的金属间化合物相的可控转变。预期上述方法能有效降低其对氢的吸附能，优化相互之间的配体作用，实现调控材料储氢行为到改善HOR催化性能的内在转换，达到提高催化性能的目标；为进一步提高催化性能和稳定性，采用自发置换的方法，实现微量Pt壳层修饰的Pd基核壳结构催化剂的可控合成，利用核、壳之间的相互作用，达到进一步提升性能的目标。通过in-situ TEM和同步辐射技术，深入、直观地探究表面结构与催化剂性能之间的联系，建立构效关系，阐释催化剂衰减机理，进而优化催化剂设计，以期进一步推动氢氧燃料电池的发展。

缓慢的氢氧化反应动力学是制约碱性膜燃料电池实现低Pt/非Pt催化剂的关键因素之一。本项目以地壳中储量较Pt丰富的Pd为研究对象，通过理性的模型构筑，对其进行尺寸优化、合金化改性以及功能化替代等方式的进一步处理，结合后续的构、性表征，从而建立起催化剂结构与活性之间的构效关系，着重分析不同功能序构之间的特定分工以及协同机制，实现从分子、原子级别的微观水平上深入理解催化反应本质的目标。主要从三个方面进行了探究：.（1）.构筑Pd@Pt核壳结构模型，通过优化Pd纳米晶的颗粒尺寸，识别碱性HOR中反应物种的类别，分析各组分间的协同机制及影响反应速率的主要因素。.（2）.引入亲氧性更强的3d过渡金属M（M=Fe，Co和Cu），构筑PdM@Pt模型，针对现存的争论焦点“氢结合能理论（HBE）和亲氧性理论”进行辨别，建立普适性的活性描述符，指导催化剂设计。.（3）.探究高稳定催化剂的优化策略，构筑PdIr@Pt模型，从微观层面分析各功能基元之间的协同效应。.本项目关于碱性氢氧化反应催化剂的研究进展为后续高效催化剂的发展提供一定的理论指导意义和实际使用价值。