Engineering asymmetric PEM for stable fuel cells at various RHs.

In this study, we tackle the complex and unresolved challenge of optimizing the performance of membrane electrode assemblies (MEAs) in varying relative humidity environments, which is crucial for practical fuel cell technologies. To address this challenge, we developed an innovative approach by fabricating an asymmetric membrane that integrates an ultrathin layer of hydrophilic carbon nanotubes (HCNTs) on the cathode side of the proton exchange membrane (PEM). The primary objective was to enhance the dimensional stability of the membrane by reducing water flooding-induced swelling on the cathode side. Additionally, the inclusion of the carbon nanotube layer improved the interfacial affinity with the cathode electrode. As a result, the MEA constructed using the asymmetric PEM coated with 0.065 mg cm−2 HCNTs demonstrated impressive current densities of 800 mA cm−2 and 1300 mA cm−2 at 0.7 V and 0.6 V, respectively, while achieving a maximum power density of 818 mW cm−2 under 100% relative humidity (RH). Remarkably, even when the RH was reduced to 0%, the MEA maintained a current density of 1100 mA cm−2 at 0.6 V and a maximum power density of 788 mW cm−2. Furthermore, the inclusion of the HCNTs layer significantly enhanced the stability of the MEA under low RH conditions, representing a crucial advancement in extending the lifespan of fuel cells in harsh environments. The novel structure of the MEA presented in this work offers a practical and effective strategy for enhancing the performance and stability of proton exchange membrane fuel cells (PEMFCs) insensitive to changing relative humidities. • A three-dimensional interface structure is achieved by coating HCNTs onto PEM for enhanced electrochemical performance. • The MEA performance improves in low or zero humidity with an HCNTs layer on the PEM's cathode side. • The HCNTs layer enhances water management by promoting water back diffusion from the cathode to the anode. [ABSTRACT FROM AUTHOR]