催化学报

催化学报 ›› 2016, Vol. 37 ›› Issue (7): 988-993.DOI: 10.1016/S1872-2067(16)62481-6

• 快讯 • 上一篇    下一篇

Nafion含量对直接甲醇燃料电池阴极催化剂性能表达的影响

龙志a,b, 邓光荣a,c, 刘长鹏a,d, 葛君杰a,d, 邢巍a,d, 马树华b   

  1. a. 中国科学院长春应用化学研究所电分析化学国家重点实验室, 吉林 长春 130022;
    b. 济南大学化学化工学院, 氟化学化工材料山东省重点实验室, 山东 济南 250022;
    c. 中国科学院大学, 北京 100049;
    d. 中国科学院长春应用化学研究所先进电源实验室, 吉林 长春 130022
  • 收稿日期:2016-03-29 修回日期:2016-05-03 出版日期:2016-06-17 发布日期:2016-06-17
  • 通讯作者: Wei Xing, Shuhua Ma
  • 基金资助:

    国家重点基础研究发展计划(973计划,2012CB932800);国家自然科学基金(21433003,21373199);吉林省科技研究项目(20150101066JC,20160622037JC).

Cathode catalytic dependency behavior on ionomer content in direct methanol fuel cells

Zhi Longa,b, Guangrong Denga,c, Changpeng Liua,d, Junjie Gea,d, Wei Xinga,d, Shuhua Mab   

  1. a. State Key Laboratory of Electroanalytical Chemistry, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun 130022, Jilin, China;
    b. Shandong Provincial Key Laboratory of Fluorine Chemical Materials, School of Chemistry and Chemical Engineering, University of Jinan, Jinan 250022, Shandong, China;
    c. University of Chinese Academy of Sciences, Beijing 100049, China;
    d. Laboratory of Advanced Power Sources, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun 130022, Jilin, China
  • Received:2016-03-29 Revised:2016-05-03 Online:2016-06-17 Published:2016-06-17
  • Contact: Wei Xing, Shuhua Ma
  • Supported by:

    This work was supported by the National Basic Research Program of China (973 Program, 2012CB932800), the National Natural Science Foundation of China (21433003, 21373199), and the Science & Technology Research Programs of Jilin Province (20150101066JC, 20160622037JC).

PDF

1050

被引次数

2

摘要：

燃料电池是一种将燃料反应的化学能转化为电能的装置,可分为氢氧质子交换膜燃料电池(PEMFCs)、直接甲醇燃料电池(DMFCs)和直接甲酸燃料电池等.与PEMFCs相比,DMFCs以甲醇为燃料,燃料的储存运输和电池操作运行具有较高的安全性,所以近年来受到人们的广泛关注.膜电极组件(MEA)是DMFCs的核心部分,由气体扩散层(GDL)、催化层(CL)和质子交换膜(PEM)三部分组成.GDL用于提高电池传质能力,并同时作为MEA的集流体.PEM主要用于隔离燃料和氧气,进行质子传导.CL是MEA中的主要组成部分,为电化学反应提供场所.催化层由催化剂,质子传输介质和电子传输介质组成.通常,阳极催化剂采用PtRu/C,阴极采用Pt/C,质子传输介质为全氟磺酸树脂,如Nafion.CL的结构对电池性能有直接的影响,因此人们对CL的结构进行了详细的研究,并通过调节CL亲水性能、梯度催化层的结构设计等优化其结构.研究表明,当CL中Nafion含量为33wt.%,PEMFCs具有最佳的电池性能.DMFCs与PEMFCs对MEA要求不同,其阴极更容易发生水淹现象.本文结合非接触式三维光学轮廓仪、接触角测试系统和电化学测试对阴极不同Nafion含量的膜电极进行了表面形貌、亲水性、循环伏安和DMFC性能测试.本文利用喷涂法制备了GDE,然后与Nafion115热压形成MEA.由三维表面形貌图可以看出,随着催化层中Nafion含量的增加,GDE表面的粗糙度变大,尤其是N35和N45.理论上,表面粗糙有利于Pt的暴露和传质扩散,但是其电池性能并未与粗糙度呈现出正相关的关系,因为Nafion含量高于35wt.%,Pt被Nafion过度包裹,抑制了O2至催化剂表面的传输,且随着Nafion含量由15wt.%增加至45wt.%,其GDE表面的接触角由166.8°减至143.1°,说明CL的亲水性增强,易导致阴极产生的水无法及时排出,从而造成阴极水淹现象.从不同Nafion含量制备MEA的CV图可以看出,随着Nafion含量的增加,Pt的电化学活性面积(ESA)增加.当Nafion含量较少时,Nafion无法对全部Pt纳米粒子(NPs)形成包覆或无法形成连贯的质子传输通道,从而导致大部分的PtNPs催化活性较低变为无效Pt.而有效PtNPs要求与连贯的质子传输通道相连接.当Nafion含量高于35wt.%时,其ESA基本保持不变,因为Pt载量一定,从而限制了ESA,此时达到该载量条件下的极限ESA.但是电池极化曲线表明,30wt.%Nafion含量的MEA具有最佳的电池性能.因为有效PtNPs不一定是高效的,当他们全部被Nafion包裹后,O2只能依靠溶解在Nafion中才可以到达催化剂表面,从而阻碍传质.只有PtNPs表面包裹和暴露面积达到一定比例时才变得高效.所以当Nafion含量低于30wt.%时,主要由质子传输通道导致的有效PtNPs较少;当Nafion含量高于30wt.%时,出现Nafion过度包裹PtNPs,阻碍O2传质.因此,Nafion含量30wt.%时,Pt的包裹面积和裸露面积达到所研究的最佳状态.

关键词: 直接甲醇燃料电池, 催化层, Nafion, 阴极, 离聚体

Abstract:

Cathode catalyst layers (CLs) with varying ionomer (Nafion) contents were prepared and the direct methanol fuel cell structure and catalytic behavior were investigated as a function of ionomer content. CL roughness and thickness increased with increasing Nafion content. Contact angle measurements determined that CL hydrophilicity also increased as a function of Nafion content. Poor bonding between the CL, microporous layer, and the proton exchange membrane was obtained when the ionomer content was too low. The electrochemical surface areas (ESAs) were found to increase with increasing Nafion content before reaching an asymptote at elevated loading levels. However, upon increasing the ionomer content above 30 wt.%, the water and oxygen mass transfer properties were difficult to control. Considering the above conditions, N30 (30 wt.% Nafion) was found to be the optimal level to effectively extend the three-phase boundaries and enhance cell performance.

Key words: Direct methanol fuel cells, Catalyst layer, Nafion, Cathode, Ionomer