Influence of Support Characteristics on the Coverage of Ionomer and Oxygen Reduction Performance on Pt/C Catalysts

doi:10.15541/jim20250004

Abstract

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

CLC Number:

TQ426

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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