载体特性对Pt/C催化剂上离聚物覆盖度及氧还原性能的影响

doi:10.15541/jim20250004

摘要/Abstract

摘要： 碳载体是质子交换膜燃料电池膜电极常用Pt/C催化剂的重要组成部分,离聚物是构成膜电极催化层的关键成分之一。本研究针对六种不同类型的商业化碳载体(VC、KB1、KB2、BP、SJR、AB),采用多种表征手段系统分析了碳载体、Pt/C催化剂以及添加离聚物之后的微观结构与表面化学性质,并且测试了各类Pt/C催化剂的氧还原反应(ORR)性能,以探究代表性碳载体负载Pt催化剂的电催化构效关系。研究发现,具有大比表面积和丰富孔结构的碳载体,如KB1、KB2、BP,可减小沉积的Pt粒径。强亲水的实心碳载体(VC,SJR)上的含氧官能团也有助于分散Pt粒子。同时,含有大量2~8 nm介孔的碳载体(KB1,KB2)有利于Pt分布在碳颗粒内孔中,而微孔(<2 nm)居多的大比表面积碳载体(BP)以及中等与低比表面积碳载体(VC、SJR、AB)上,绝大部分Pt粒子分布在碳颗粒外表面。进一步结合离聚物加入前后Pt/C样品比表面积与孔结构的变化,测算离聚物的覆盖度,并提出了离聚物在催化剂颗粒上的分布模型。在实心碳负载催化剂上,一定量的离聚物基本覆盖了碳颗粒外表面;在微孔主导的BP负载催化剂上,离聚物可堵塞微孔,造成比表面积与孔容大幅下降;而在介孔碳负载的催化剂上,相同量的离聚物不足以堵塞全部微孔(<2 nm)与介孔(2~8 nm),使得覆盖度较低。Pt/C催化剂的ORR活性主要决定于Pt粒径大小,并且,分布在碳颗粒内孔的Pt粒子可免受离聚物的毒化,因此,KB系列碳载体负载的Pt催化剂在液相ORR动力学过程中表现优异。

关键词: 载体特性, Pt/C催化剂, 离聚物覆盖度, 氧还原反应, 质子交换膜燃料电池

Abstract: Carbon support is an important component of Pt/C catalyst commonly used in the membrane electrodes of proton exchange membrane fuel cells, and ionomer is one of the key components that make up the catalytic layer. In the present study, six different types of commercial carbon supports (VC, KB1, KB2, BP, SJR, AB) were focused. The microstructure and surface chemical properties of the carbon supports and the Pt/C catalysts prepared pre and post the addition of ionomer were investigated using various characterization methods. The oxygen reduction reaction (ORR) performance of various Pt/C catalysts was tested to explore the electrocatalytic structure-activity relationship of representative carbon supported Pt catalysts. As revealed, carbon supports with large specific surface areas and rich pore structures, such as KB1, KB2 and BP, contributes to more uniform distribution of Pt particles and smaller particle size. The presence of oxygen-containing functional groups on solid carbon supports with strong hydrophilicity, such as VC and SJR, contributes to the dispersion of Pt particles. Meanwhile, carbon supports with abundant mesopores in the range of 2-8 nm (KB1 and KB2) are beneficial for improving the location of Pt within the pores of carbon particles, while those with high specific surface area and full of micropores (BP) and with medium or low specific surface area (VC, SJR, AB) have most Pt nano-particles distributed on the outer surface of the carbon particles. By further combining the changes in specific surface area and pore structure of various Pt/C samples before and after the addition of ionomer, the coverages of ionomer were calculated, and a distribution model of ionomer on different catalyst particles was proposed. On the solid carbon supported catalysts, a certain amount of ionomer basically covers the entire outer surface of carbon particles. On the BP supported catalyst which is dominated by micropores, ionomer can block the micropores, resulting in a significant decrease in specific surface area and pore volume; on the mesoporous carbon supported catalysts, the same amount of ionomer is hard to block all micropores and mesopores, leading to lower coverages. The ORR activity of Pt/C catalyst mainly depends on the Pt nano-particle size, and the Pt nano-particles located in the pores inside the carbon particles can be protected from the poisoning of ionomer. Therefore, Pt catalysts supported on the carbon supports of KB series exhibit excellent performance for the ORR kinetics occurring in liquid-phase.

Key words: support characteristic, Pt/C catalyst, ionomer coverage, oxygen reduction reaction, proton exchange membrane fuel cell

中图分类号:

TQ426

李薛茹, 马哲杰, 郭宇杰, 李平. 载体特性对Pt/C催化剂上离聚物覆盖度及氧还原性能的影响[J]. 无机材料学报, DOI: 10.15541/jim20250004.

LI Xueru, MA Zhejie, GUO Yujie, LI Ping. Influence of Support Characteristics on the Coverage of Ionomer and Oxygen Reduction Performance on Pt/C Catalysts[J]. Journal of Inorganic Materials, DOI: 10.15541/jim20250004.

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