Atomically thin CVD graphene-integrated proton exchange membrane electrode assemblies: fabrication parameter space and hydrogen crossover mitigation

Abstract

Proton selective, atomically thin two-dimensional (2D) materials interfaced with state-of-the-art proton exchange membranes (PEMs) enable overcoming the inherent trade-off between proton conductance and gas crossover. Monolayer graphene-integrated PEMs show significantly reduced gas crossover with negligible impact on proton conductance. However, the influence of fabrication methods on membrane–electrode assemblies (MEAs) using PEMs interfaced with monolayer graphene (synthesized via chemical vapor deposition (CVD)) via an ultra-thin (∼700 nm) ionomer carrier layer remains elusive. Here, we systematically investigate three MEA fabrication processes: gas diffusion electrode (GDE), directly sprayed catalyst-coated membrane (DS-CCM), and decal transfer catalyst-coated membrane (DT-CCM) using monolayer CVD graphene-integrated with perfluorosulfonic acid (PFSA) PEMs (∼12–25 μm thick). Although the GDE process minimizes processing or impact on PEM properties, the rough surface of the GDE could damage CVD graphene coated with the ∼700 nm ionomer carrier layer, limiting the suppression of H₂ crossover. The DS-CCM approach exposes the PEM to solvents, resulting in degradation and diminished performance. DT-CCM emerges as the most effective route, with minimal graphene damage, yielding a pronounced reduction (∼25–44%) in H₂ crossover without impacting proton conductance. Notably, the decal approach remains effective even for thinner (∼12 μm thick) PEMs with inherently higher proton conductance, where reduced crossover can enable enhanced membrane durability and fuel cell efficiency. These findings establish fabrication-sensitive design rules for integrating 2D materials into MEAs and highlight the advantages of the decal-transfer approach for next-generation PEMs.