Evaluation of Graphene Nanoplatelets as a Microporous Layer Material for PEMFC: Performance and Durability Analysis

In this paper, the effect of different carbonaceous phases in microporous layers (MPLs) for polymer electrolyte membrane fuel cells (PEMFCs) is reported. A conventional ink with carbon black (CB) powder and an innovative one featuring graphene nanoplatelets (GNPs) have been produced and used to coat carbon cloth gas diffusion layers (GDLs). Morphological and electrical properties of these samples have been assessed and then compared to determine which characteristics contribute to a possible enhancement of the fuel cell performance. Static contact angle measurements have revealed a similar hydrophobic character for both samples. Through-plane water permeability and porosity of the samples have been correlated to the optimal working temperature: GNPs-based MPLs provide the best performance in dry condition (T = 80 °C, RH = 60%), while CB-based samples work better in more humid conditions. Instead, the electrical conductivity of the samples have not displayed a strong influence on the polarization curve of the cell. In addition, an ex situ mechanical accelerated stress test (AST) has been performed on both samples to assess their durability and understand which factors could lengthen their lifetime. GNPs-based samples resisted better under the harsh conditions imposed during the AST and a possible optimization of this ink composition is proposed for future development