晶面可控铂钯基纳米晶上电催化的表面增强红外光谱研究

"Mild and effective surface decontamination", "in situ determination of preferential facets" and "in situ monitoring of reactions" are currently the bottlenecks for investigating electrocatalysis on facet-controlled Pt, Pd-based nanocrystals. To address these issues, we propose to replace the surface impurities on the nanocrystals which are well-synthesized based on wet-chemistry process with certain specifically adsorbed species and explore the mild and effective decontamination method. Also, we plan to apply electrochemical ATR surface enhanced IR absorption spectroscopy (SEIRAS) to characterize the adsorption states of probe molecules on different nanocrystal facets, check the surface cleanness and establish the relationship between spectral information and facet structures of nanocrystals. Furthermore, electrocatalytic processes of small organic fuel molecules on these facets-controlled Pt, Pd based nanocrystals in both acidic and alkaline solutions will be systematically studied with in situ ATR-SEIRAS, in order to reveal the facet dependent electrocatalytic activity and stability on the molecular level, and to provide mechanistic insights into the relevant reactions. The above integrated investigations involve a novel combination of facet-controlled nanocrystals, fuel cell-related electrocatalysis and in situ high-sensitivity spectroscopic techniques and are expected to play an important role in the development of a new generation of high performance nanoelectrocatalysts.

"表面清洁优选"、"结构现场表征"和"反应现场监测"三大问题是现阶段Pt、Pd基晶面优先取向的纳米晶电催化研究的瓶颈。针对此现状，本课题中拟采用特性强吸附物种来置换表面杂质，探索温和、有效的纳米晶清洗方法；结合电化学衰减全反射表面增强红外光谱方法表征探针分子在不同纳米晶面的吸附状态，同时检验晶面的清洁程度；进而应用上述现场红外光谱方法研究在酸、碱性溶液中不同晶面优先取向的Pt、Pd基纳米晶上小分子燃料阳极电催化过程，从分子水平上揭示"纳米晶面-反应性质"关系，澄清相关反应机理。以上研究促进晶面可控纳米单晶（材料）、燃料电池相关电催化（反应）和现场高灵敏光谱技术（方法）三方面有机结合，对创制新一代高性能Pt、Pd基纳米电催化剂具有重要意义。

为研究纳米晶上碱性乙醇、乙二醇和甲酸的催化电氧化，合成了多种形貌及结构可控的Pt、Pd基纳米晶催化剂，如分别具有{100}、{110}和{111}晶面取向的纳米立方体、菱形十二面体和八面体，具有{hk0}高指数晶面的Pd内凹立方体，Pt单层覆盖的立方体、菱形十二面体和八面体Au纳米晶Au@Pt核壳结构，以及碳载型Pd-Ni-P和Pd-Pt-Cu三元合金纳米催化材料。为获得纳米晶上可靠的电催化行为，发展了高效去除纳米晶表面活性剂的方法，如CO吸附置换法和析氢区控电位法等。应用原位衰减全反射表面增强红外光谱技术（ATR-SEIRAS）对表面清洁过程进行实时动态检测，并结合非原位XPS元素分析技术进行验证。利用ATR-SEIRAS方法表征催化材料的特定结构，如以CO探针分子的谱学特征区分Au上单层Pt与多层Pt结构，以及判定表面离散型Pt原子的稳定性。结合ATR-SEIRAS与外反射红外吸收光谱技术，研究了Pd内凹立方体纳米晶在Bi修饰前后对碱性溶液中乙二醇电氧化反应机理与产物分布的差异性。通过本项目研究我们共发表了18篇SCI论文，其中中科院一区论文11篇，国际会议特邀报告4次。本项目的实施促进了纳米晶材料制备、表面清洗及其在燃料电池电催化中的应用，拓展了原位红外光谱方法在纳米晶上的电催化反应机理研究，从分子水平揭示了“纳米晶面-反应性质”关联性，为理性合成高效纳米晶催化剂奠定必要的基础。