The performance and durability of high-temperature proton exchange membrane fuel cells enhanced by single-layer graphene

Single-layer graphene (SLG) obtained by chemical vapor deposition is applied between membrane and electrodes by a wet chemical transfer method to study its effect on the performance and durability of polybenzimidazole membranes in high-temperature proton exchange membrane fuel cells (HT-PEMFCs). After accelerated stress testing (AST), the membrane electrode assembly (MEA) loaded with SLG at different positions exhibits higher peak power density, lower electrode resistances, and larger electrochemical active surface area than pure polybenzimidazole membranes with high phosphoric acid doping level. The peak power density of the MEAs with both cathode and anode loaded with SLG is 480 mW cm^-2 after AST, while those based on pure membranes is 249 mW cm^-2. Lab-based X-ray micro-computed tomography combined with Raman spectroscopic mapping was applied for the first time to study the effect of SLG on controlling phosphoric acid leaching. In addition, samples containing SLG on an ultra-thin membrane (7.5 µm) were also tested to explore its influence on hydrogen crossover. After 100 h of galvanostatic discharging, the hydrogen crossover of samples loaded with single-layer graphene on the anode does not exceed 1.75 × 10⁻⁴ mol s^-1, which is much lower than that of MEAs made using pure ultra-thin membranes (8.16 ×10⁻⁴ mol s^-1).