催化学报 ›› 2019, Vol. 40 ›› Issue (4): 504-514.DOI: 10.1016/S1872-2067(19)63304-8

• 论文 • 上一篇    下一篇

微量Co修饰的碳载超细Pt纳米粒子的制备及其在燃料电池氧还原催化中的应用

唐雪君a,b, 方达晖a,b, 瞿丽娟a,b, 徐东彦c, 秦晓平a, 覃博文a,b, 宋微a, 邵志刚a, 衣宝廉a   

  1. a 中国科学院大连化学物理研究所, 燃料电池系统与工程实验室, 辽宁大连 116023;
    b 中国科学院大学, 北京 100049;
    c 青岛科技大学化工学院, 生态化学工程国家重点实验室基地, 山东青岛 266042
  • 收稿日期:2018-12-01 修回日期:2019-01-11 出版日期:2019-04-18 发布日期:2019-03-14
  • 通讯作者: 邵志刚
  • 基金资助:

    国家重点研发计划(2016YFB0101208);国家自然科学基金(21576257);NSFC-辽宁联合基金(U1508202);中国科学院战略性先导科技专项(B类)(XDB06050303).

Carbon-supported ultrafine Pt nanoparticles modified with trace amounts of cobalt as enhanced oxygen reduction reaction catalysts for proton exchange membrane fuel cells

Xuejun Tanga,b, Dahui Fanga,b, Lijuan Qua,b, Dongyan Xuc, Xiaoping Qina, Bowen Qina,b, Wei Songa, Zhigang Shaoa, Baolian Yia   

  1. a Fuel Cell System and Engineering Laboratory, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian 116023, Liaoning, China;
    b University of Chinese Academy of Sciences, Beijing 100049, China;
    c State Key Laboratory Base of Eco-chemical Engineering, College of Chemical Engineering, Qingdao University of Science and Technology, Qingdao 266042, Shandong, China
  • Received:2018-12-01 Revised:2019-01-11 Online:2019-04-18 Published:2019-03-14
  • Supported by:

    This work was supported by the National Major Research Project (2016YFB0101208), the National Natural Science Foundation of China (21576257), the Natural Science Foundation-Liaoning United Fund (U1508202), and the Strategic Priority Research Program of the Chinese Academy of Sciences (XDB06050303).

摘要:

质子交换膜燃料电池(PEMFC)具有清洁、高效等优点,是一种理想的汽车动力电源.然而,由于其阴极氧还原反应(ORR)速率缓慢,需要使用大量的Pt基催化剂,导致燃料电池成本居高不下,严重制约了PEMFC的商业化发展.将Pt与过渡金属Fe,Co,Ni等形成合金,对表面Pt原子的几何结构和电子结构进行调变,可以有效提高催化剂的活性,实现Pt用量和燃料电池成本的降低.但是目前合金催化剂多采用溶剂热、浸渍-高温退火等制备方法,使用有毒有害试剂和难清洗的表面活性剂,且过程复杂、能耗高,不利于大规模化生产.此外,合金中过渡金属占比高,在燃料电池工况下,大量过渡金属溶解,加速了膜的降解,导致实际PEMFC性能的降低.对此,我们探索了一种简便有效的方法制备高活性、高稳定性的碳载Pt-Co催化剂.在没有添加表面活性剂的情况下,采用硼氢化钠辅助乙二醇还原法合成了具有超小尺寸和均匀分布的Pt-Co纳米颗粒,后续酸刻蚀处理去除不稳定的Co原子,重组双金属纳米颗粒的表面结构形成富Pt壳层,进一步提高了催化剂的活性和稳定性.通过电感耦合等离子体、X射线粉末衍射、透射电子显微镜、高分辨透射电子显微镜、高角环形暗场-扫描透射-元素分布及光电子能谱等物理表征证实了微量Co改性的碳载超细铂合金纳米颗粒的组成和结构.进一步对催化剂进行旋转圆盘电极和单电池测试,结果表明,Pt36Co/C具有明显高于商业化Pt/C的有效电化学活性面积和电池性能.此外,加速衰减测试和衰减前后的电镜图片表明,Pt36Co/C催化剂的稳定性相较于Pt/C亦有所增强.分析Pt-Co/C催化性能提高的原因,主要归于以下三点:(1)催化剂纳米颗粒在载体上分布均匀,且具有超小的粒径尺寸,提供了大量的三相反应界面位点;(2)双金属配体和电子效应的协同作用,降低了氧化物质在催化表面的吸附能力,加速了ORR的电催化动力学;(3)酸蚀刻导致的不稳定Co的溶解及催化剂表面结构的重排,形成了富Pt壳层结构,有利于提高催化剂的稳定性.这种简单有效的合金制备方法可以在电催化领域推广使用.

关键词: 质子交换膜燃料电池, 氧还原反应, 超细Pt纳米粒子, 微量Co修饰, 改进的乙二醇还原法, 酸刻蚀

Abstract:

To accelerate the kinetics of the oxygen reduction reaction (ORR) in proton exchange membrane fuel cells, ultrafine Pt nanoparticles modified with trace amounts of cobalt were fabricated and decorated on carbon black through a strategy involving modified glycol reduction and chemical etching. The obtained Pt36Co/C catalyst exhibits a much larger electrochemical surface area (ECSA) and an improved ORR electrocatalytic activity compared to commercial Pt/C. Moreover, an electrode prepared with Pt36Co/C was further evaluated under H2-air single cell test conditions, and exhibited a maximum specific power density of 10.27 W mgPt-1, which is 1.61 times higher than that of a conventional Pt/C electrode and also competitive with most state-of-the-art Pt-based architectures. In addition, the changes in ECSA, power density, and reacting resistance during the accelerated degradation process further demonstrate the enhanced durability of the Pt36Co/C electrode. The superior performance observed in this work can be attributed to the synergy between the ultrasmall size and homogeneous distribution of catalyst nanoparticles, bimetallic ligand and electronic effects, and the dissolution of unstable Co with the rearrangement of surface structure brought about by acid etching. Furthermore, the accessible raw materials and simplified operating procedures involved in the fabrication process would result in great cost-effectiveness for practical applications of PEMFCs.

Key words: Proton exchange membrane fuel cells, Oxygen reduction reaction, Ultrafine Pt nanoparticles, Trace amounts of cobalt, Modified glycol method, Chemical etching strategy