通过原位还原碳化技术增强碳化钨类铂电催化性能研究

Direct methanol fuel cell (DMFC) is still far from large-scale commercial production mainly because commercial Pt/C catalyst has some shortcomings such as high price, easy to poisoning and oxidization of carbon support and so on. WC has the advantages of surface electronic structure like Pt, good conductivity and resistance to acid and poison, which is widely studied as a potential alternative to the noble metal catalytic materials. But there is a wide gap between the electro-catalytic activities of Pt and WC. How to improve the electro-catalytic properties of WC like platinum, which is a difficult problem faced by scientists.To solve these problem above, We designed a core-shell structure catalyst which was composed by WO3 microsphere as nuclear and Pt + WC as shell. The surface of WO3 microsphere was transformed into WC by in situ reduction carbonization technology, and modern physical technology and chemical methods were employed for the surface treatment. The electro-catalytic properties like Pt of WC were improved due to reduce the content of surface carbon and increase the number of carbon defects on the surface of WC. The performances of methanol electro-oxidation and oxygen reduction were improved by designing and controlling microstructure, chemical composition and valence state of Pt and WC shell, which will solve some shortcomings of commercial Pt/C catalyst above mentioned.

直接甲醇燃料电池（DMFC）距离大规模商业化生产还有些距离，主要是因为商业碳载铂催化剂存在贵金属价格高、易中毒和碳载体易氧化等缺点。WC具有和Pt相似的表面电子结构、良好的导电性、抗中毒性和耐酸性等优点，作为一种潜在的能够替代贵金属催化材料并而被广泛研究。但是WC的电催化活性与Pt相比还有很大差距，如何提高WC的类铂电催化性能成为科学家面临的一个难题。针对以上问题，本项目设计一种以WO3微球为核，Pt + WC为壳的核壳结构电催化剂（Pt-WC/WO3）。采用原位还原碳化技术，将WO3微球表面部分被还原碳化转变为WC，结合现代物理技术和化学方法对其表面处理，有效降低WC表面积碳和增加WC表面碳缺陷，增强WC类铂电催化性能。通过对Pt + WC壳层微结构、化学组成和价态的设计与控制，提高催化剂对甲醇氧化和氧还原反应的电催化性能，解决目前商业碳载铂催化剂存在的上述问题。

WC具有和Pt相似的表面电子结构，作为一种潜在的能够替代Pt族贵金属催化材料而被广泛关注，可是WC的电催化性能与贵金属相比还有很大差距，限制了其在直接甲醇燃料电池（DMFC）的应用。本项目采用喷雾干燥法制备的偏钨酸铵微球作为前驱体，然后利用原位还原碳化技术对微球表面进行改性研究，并分别借助湿化学还原法和原位电化学反应制备三种具有核壳结构的电催化剂（Pt-WO2/WO3、Pt-WC/WO3和Pd/WC）。通过对壳层微结构、化学组成和价态设计与控制，提高催化剂对甲醇/甲酸氧化反应的电催化性能，有效解决商业催化剂存在贵金属价格高、易中毒和碳载体稳定性差等问题。同时还拓展研究利用本项目中喷雾干燥技术制备了三维结构的石墨烯材料，有效解决传统二维石墨烯团聚问题，该研究成果为制备高性能DMFC催化剂提供了一种新方法。研究成果共发表SCI和EI论文7篇，其中TOP期刊论文2篇，申请发明专利2项。培养硕士研究生1名和博士后1名，项目组成员赴国内进行学术交流2次。在项目执行中取得的主要代表性成果如下：1）首次采用喷雾干燥法和原位还原技术合成了具有核壳结构的WO2/WO3微球，具有导电性能的WO2修饰添加能加快电化学反应过程中电子转移速率，提高了Pt-WO2/WO3催化剂对甲醇电催化性能；2）在上述研究基础上，进一步优化原位还原碳化反应温度和时间等工艺参数，合成了具有核壳结构的Pt-WC/WO3催化剂。结果发现WC微球表面积碳对甲醇电催化反应有抑制作用，而少量WO3对甲醇电催化反应有促进作用；3）采用喷雾干燥法和还原炭化处理制备具有中空介孔结构的WC-Co复合粉。利用碳化钨钴复合粉表面的钴和氯化钯发生原位电化学反应，得到纳米Pd/WC 催化剂，研究结果表明Pd/WC催化剂比Pd /C催化剂对甲酸呈现出更高的电催化氧化活性和稳定性。