基于LDHs法Au-Cu双金属纳米催化剂的可控制备及CO-PROX催化性能研究

CO preferential oxidation in presence of hydrogen (CO-PROX) is an effective way to avoid poisoning of Pt electrode for PEMFC application. The catalytic behaviors of bimetallic Au-Cu catalyst for CO-PROX is closely related to their microstructure (particle size, surface element distribution and crystalline phase) and surface hydroxyl (distribution density and site). However, it is difficult to get nano Au-Cu bimetallics with small particle size and homogenous distribution of surface element by the traditional method. In this project, based on layered double hydroxides method, Au-Cu bimetallics with controllable nano size and homogenous surface element distribution could be prepared by direct anion exchange method in one pot. Based on the above results, according to the memory-structure effect of LDO, the hydroxyl group will be controlled by addition of alkali metal into the recover media and water gas into thermal pretreatment. The relationship between the structure of catalyst (nano size, distribution of surface element, crystal phase and surface hydroxyl) and catalytic performances in CO-PROX reaction will also be investigated by a combination of appropriate characterization and activity evolution. The promotion reaction mechanism by hydroxyl group will be discussed combination with the results of in situ FTIR, online MS and analysis of kinetics. The progress in this research could provide a new sight in preparation of gold based bimetallic catalysts for effectively catalyzed CO-PROX reaction.

H2中CO选择氧化（CO-PROX）是解决在线制氢， 防止质子交换膜燃料电池中毒的有效方法。CO-PROX用Au-Cu双金属催化剂的催化性能与其微观结构（晶粒尺寸、表面元素分布、晶相）和表面羟基（分布密度和位点）密切相关。针对常规制备难以获得颗粒尺寸小、表面元素分布均匀且表面羟基可控的Au-Cu双金属纳米催化剂，本课题拟以类水滑石（LDHs）为前驱体，通过阴离子配位交换一步合成微观结构可控的Au-Cu双金属；在此基础上，利用LDO的结构记忆效应，通过引入含碱金属的复原介质和热处理过程中的水蒸气调控催化剂表面羟基；结合物化表征技术表征催化剂理化性质，优化制备条件，考察其对CO-PROX反应的催化性能，建立微观结构和表面羟基与催化性能之间的构效关系，结合原位红外和在线质谱以及动力学分析探讨微观结构和表面羟基促进CO选择氧化机理，为开发设计高效CO-PROX反应用催化剂提供新的思路和理论参考。

H2中CO选择氧化（CO-PROX）是解决在线制氢,防止质子交换膜燃料电池中毒的有效方法，同时低温CO氧化也是消除污染物CO的有效方法。本研究针对CO氧化用Au-Cu双金属催化剂的催化性能与其微观结构（晶粒尺寸、表面元素分布、晶相）和表面羟基（分布密度和位点）密切相关，开展了调制微观结构和表面羟基的Au-Cu双金属催化剂，测试富氢/非氢条件下的CO氧化性能以及建立构-效关系。我们发现：（1）CO吸附在Au位点，而O2吸附在AuCu合金位点上；动力学分析结果认为CO氧化反应在具有AuCu合金的催化剂上遵循Langmuir-Hinshelwood-type（L-H）机理。（2）基于类水滑石前驱体一步制备和两步制备Au-Cu/AlCeO催化剂用于CO-PROX性能研究。实验结果表明，一步制备的Au-Cu/AlCeO催化剂经过焙烧再还原后的催化活性和稳定性均高于相同热处理条件下两步制备的Au-Cu/AlCeO催化剂；水滑石载体添加Ce成分，调变了活性氧物种分布，有利于提高CO-PROX性能；氢气浓度增加，CO-PROX性能提升。（3）基于共沉淀法制备的Co基非贵金属催化剂经焙烧还原后表面富羟基，表现出较好的CO-PROX性能。依托本项目的研究结果，为开发设计高效CO-PROX反应用催化剂提供了一定的借鉴。