催化学报 ›› 2018, Vol. 39 ›› Issue (4): 790-799.DOI: 10.1016/S1872-2067(17)62982-6

• 论文 • 上一篇    下一篇

非贵金属钴、氮共掺杂碳纳米管负载纸衍生多孔碳电催化剂的制备及其氧还原性能研究

刘高鹏a, 王彬a, 徐丽a, 丁鹏辉a, 张鹏飞b,c, 夏杰祥a,b, 李华明a, 钱君超d   

  1. a 江苏大学化学化工与能源研究院, 江苏镇江 212013, 中国;
    b 橡树岭国家实验室化学科学部, 橡树岭 37830, 美国;
    c 上海交通大学化学化工学院, 上海 200240, 中国;
    d 苏州科技大学江苏省环境功能材料重点实验室, 江苏苏州 215009, 中国
  • 收稿日期:2017-11-21 修回日期:2017-12-23 出版日期:2018-04-18 发布日期:2018-04-08
  • 通讯作者: 夏杰祥, 李华明
  • 基金资助:

    国家自然科学基金(21476098,21471069,21576123);博士后国际交流计划(20150060).

Paper-derived cobalt and nitrogen co-doped carbon nanotube@porous carbon as a nonprecious metal electrocatalyst for the oxygen reduction reaction

Gaopeng Liua, Bin Wanga, Li Xua, Penghui Dinga, Pengfei Zhangb,c, Jiexiang Xiaa,b, Huaming Lia, Junchao Qiand   

  1. a School of Chemistry and Chemical Engineering, Institute for Energy Research, Jiangsu University, Zhenjiang 212013, Jiangsu, China;
    b Chemical Sciences Division, Oak Ridge National Laboratory, Oak Ridge 37830, USA;
    c School of Chemistry and Chemical Engineering, Shanghai Jiao Tong University, Shanghai 200240, China;
    d Jiangsu Key Laboratory for Environment Functional Materials, Suzhou University of Science and Technology, Suzhou 215009, Jiangsu, China
  • Received:2017-11-21 Revised:2017-12-23 Online:2018-04-18 Published:2018-04-08
  • Contact: 10.1016/S1872-2067(17)62982-6
  • Supported by:

    This work was supported by the National Nature Science Foundation of China (21476098, 21471069, 21576123) and International Postdoctoral Exchange Fellowship Program of China Postdoctoral Council (20150060).

摘要:

燃料电池可以直接将化学能转化为电能,是一种极具前景的能量转换设备.目前,铂碳是燃料电池阴极氧还原反应(ORR)常用催化剂,但是铂储量低、价格昂贵、稳定性差且容易受CO毒化,极大地限制了其在燃料电池商业化中的应用.因此,探索价格低廉、性能优越的非贵金属氧还原催化剂显得尤为重要.
大量研究发现,碳基材料具有优越的氧还原性能和良好的电化学稳定性.同时,自然界的生物质种类丰富,是很好的碳基材料来源.本文选取日常生活中最常见的富碳生物质废纸作为碳源,二氰二胺和乙酰丙酮钴分别作为氮源和钴源,经过特定气氛下的梯度升温制得非贵金属钴、氮共掺杂碳纳米管负载多孔碳氧还原催化剂(Co/N/CNT@PC-800).考察了杂原子N掺杂、过渡金属Co掺杂对材料形貌和性能的影响,采用扫描电子显微镜(SEM)、透射电子显微镜(TEM)、X射线衍射(XRD)、拉曼(Raman)光谱、氮气吸附-脱附和X射线光电子能谱(XPS)等表征方法探究了Co/N/CNT@PC-800材料的组成与结构,通过循环伏安法(CV)以及线性扫描伏安法(LSV)等电化学测试探究了其氧还原反应性能.
SEM和TEM结果表明,Co/N/CNT@PC-800材料为表面生长着大量碳纳米管的多孔碳结构.这是因为二氰二胺和钴引入后,钴催化二氰二胺转化成碳纳米管.金属纳米粒子被封装在碳层之间和碳纳米管中而得到有效的保护,使之不易被酸腐蚀.同时,Co和N元素可以形成更多的活性位点(Co-Nx),增强材料ORR活性.SEM和氮气吸附-脱附结果显示,掺杂Co后,材料的介孔结构会进一步增加,形成微孔/介孔结构.多孔结构可以增强ORR相关物质(O2,H+,OH-,H2O)的传质速率,提升反应速率,达到增强ORR活性的效果.除此之外,多孔的结构也可以促进活性位点的暴露,进而提升材料的ORR性能.XPS结果显示,Co/N/CNT@PC-800材料中N主要以吡啶氮和石墨氮两种形式存在,而这两种类型的氮有利于促进ORR的进行.Raman光谱结果显示,在引入N和Co元素后,材料的缺陷结构有所增加,因而有利于电催化氧还原反应性能的提升.
另外,LSV测试结果表明,在引入Co或者N后,材料催化ORR的起始电位、半波电位、极限电流密度均有小幅改善;同时引入Co和N后,Co/N/CNT@PC-800材料催化ORR的起始电位(0.005V vs.Ag/AgCl)、半波电位(-0.173V vs.Ag/AgCl)、极限电流密度(-4.117mA cm-2)均有较大幅度的改善.通过Koutecky-Levich(K-L)方程计算以及旋转环盘电极测得的氧还原极化曲线结果均表明,Co/N/CNT@PC-800材料的氧还原反应是通过准四电子反应转移路径进行.此外,循环(3000圈CV)稳定性测试结果证明,Co/N/CNT@PC-800材料比商业化的Pt/C具有更好的稳定性.
总之,本文采用简单的梯度升温法制备出非贵金属钴、氮共掺杂的碳基氧还原催化剂(Co/N/CNT@PC-800),为探索利用生物质制备电催化剂用于燃料电池提供了一种可供选择的途径.

关键词: 氧还原反应, 废纸, 生物质, 多孔碳,

Abstract:

The oxygen reduction reaction (ORR) is a vitally important process in fuel cells. The development of high-performance and low-cost ORR electrocatalysts with outstanding stability is essential for the commercialization of the electrochemical energy technology. Herein, we report a facile synthesis of cobalt (Co) and nitrogen (N) co-doped carbon nanotube@porous carbon (Co/N/CNT@PC-800) electrocatalyst through a one-step pyrolysis of waste paper, dicyandiamide, and cobalt(Ⅱ) acetylacetonate. The surface of the hierarchical porous carbon supported a large number of carbon nanotubes (CNTs), which were derived from dicyandiamide through the catalysis of Co. The addition of Co resulted in the formation of a hierarchical micro/mesoporous structure, which was beneficial for the exposure of active sites and rapid transportation of ORR-relevant species (O2, H+, OH-, and H2O). The doped N and Co formed more active sites to enhance the ORR activity of the electrocatalyst. The Co/N/CNT@PC-800 material exhibited optimal ORR performance with an onset potential of 0.005 V vs. Ag/AgCl and a half-wave potential of -0.173 V vs. Ag/AgCl. Meanwhile, the electrocatalyst showed an excellent methanol tolerance and a long-term operational durability than that of Pt/C, as well as a quasi-four-electron reaction pathway. The low-cost and simple synthesis approach makes the Co/N/CNT@PC-800 a prospective electrocatalyst for the ORR. Furthermore, this work provides an alternative approach for exploring the use of biomass-derived electrocatalysts for renewable energy applications.

Key words: Oxygen reduction reaction, Waste paper, Biomass, Porous carbon, Cobalt