In Situ Flame-Synthesized Carbon Nanotubes on Carbon Paper as a Microporous Layer for Proton Exchange Membrane Fuel Cells

Microporous layer (MPL) is an important component of the gas diffusion layer (GDL), which can improve the mass transfer rate to enhance the performance of the proton exchange membrane fuel cell (PEMFC). Although the carbon nanotube (CNT) is a promising material for MPL, the preparation and usage of CNT in MPL have many problems, such as macropore blocking, complex and time-consuming preparation, and expensive equipment. In this paper, a simple and cost-effective flame synthesis method to prepare CNT as MPL for PEMFC is proposed. It only takes 30 s to form a three-dimensional porous structure by growing CNT on carbon paper, which changes the pore size distribution of the gas diffusion layer (GDL) and is beneficial for enhancing the mass transfer rate. The density of CNT grown inside the carbon paper is hierarchical. The catalyst of the CNT and the burning time significantly influenced the density of CNT and the properties of the GDL. The maximum power density reached 1184 mW cm –2 for the GDL prepared by this flame method, which indicates an increase by 24.2% compared to the commercial GDL. Furthermore, the analysis by electrochemical impedance spectroscopy (EIS) indicated that the mass transfer resistance of the GDL prepared by the flame method was smaller than that of the commercial GDL. These findings provide a promising approach for the preparation of MPL with CNT.