Effect of a polybenzimidazole coating on carbon supports for ionomer content optimization in polymer electrolyte membrane fuel cells

Optimizing the ionomer/carbon (I/C) ratio in the catalyst layer (CL) of polymer electrolyte membrane fuel cells (PEMFCs) is vital for maximizing PEMFC efficiency. In this study, the effect of the I/C ratio for a platinum (Pt) catalyst loaded on a polybenzimidazole (PBI)-coated Vulcan (Vulcan/PBI/Pt) is compared with a conventional Pt catalyst on Vulcan (Vulcan/Pt). Furthermore, this study determines that a CL comprising Vulcan/PBI/Pt with an I/C = 0.2 exhibits the highest maximum power density (750 mW cm−2), while that of a CL having Vulcan/Pt is calculated to be 610 mWcm−2 at I/C = 0.6. Effective interactions between ionomer and the PBI-coated Vulcan enables stable ionomer coating and high proton conductivity, even at very low I/C ratios. At such low I/C ratios, the O2 diffusion coefficient of Vulcan/PBI/Pt CL is improved by 51% when compared to Vulcan/Pt CL with an I/C = 0.6. Cross-sectional scanning electron microscopy images further reveal that Vulcan/PBI/Pt CLs possess better pore connectivity than those of Vulcan/Pt. Hence, it concludes that the proposed PBI coating approach is advantageous and significant breakthrough to fabricate highly efficient CLs by improving both proton conduction and O2 diffusion simultaneously with lower ionomer contents. •The polymer (PBI) coating induces an effective interaction with Nafion.•PBI-coating improved homogeneous Nafion coating even at a low ionomer content.•A sufficient proton conduction is achieved with a lower I/C ratio of 0.2•Lowering ionomer content improves oxygen diffusion coefficient by 51%.•PBI-coating enhances power density by 23% compared to conventional system.