Carbon nanotubes grown in situ on carbon paper as a microporous layer for proton exchange membrane fuel cells

•The GDL with in-situ grown CNTs on the fibrous carbon paper is fabricated.•A CNT/GDL with proper hydrophobicity and pore structure is obtained.•PEMFC with CNT/GDL shows better performance than the one with CB/GDL.

The performance of proton exchange membrane fuel cell (PEMFC) is greatly influenced by the characteristics of gas diffusion layer (GDL). Herein, in situ grown carbon nanotubes (CNTs) on carbon paper as a gas diffusion layer (GDL) were fabricated by a plasma-enhanced chemical vapor deposition (PECVD) process. Fuel cells using CNT-based GDLs with nickel (II) nitrate loading of 1.6 mg cm−2 show better performance compared with the GDLs which employ Vulcan XC-72 as the MPL. The pore size distribution and the gas permeability results revealed that the increasing density of CNT layer had two main effects on the pore structure of GDL: firstly, the increasing density of CNT layer decreased the macro pore volume and the open through pore volume of CNT-based GDL; secondly, the increasing density of CNT layer decreased the micro pore diameter of CNT-based GDL. The data obtained from the vapor permeability and the fuel cell performance tests indicated that the water flooding can be reduced by applying CNT-based GDLs. The electrochemical impedance spectroscopy (EIS) confirmed that the CNT-based GDL can effectively promote the mass transfer in the FCs which was attributed to its suitable hydrophobicity and proper structure.