Electrospun catalyst layers using short-side-chain ionomer for low platinum and high performance PEMFCs

Abstract

Proton exchange membrane fuel cells (PEMFCs) should further reduce the platinum consumption to lower their manufacturing costs and life-cycle carbon emissions. However, the performance of the catalyst layers with low-Pt loading needs to be improved. Short-side-chain (SSC) ionomers have been proven to enhance the catalytic activity of conventional catalyst layers. In this work, the SSC ionomer was applied to the electrospun catalyst layer, and achieved a remarkable improvement in the performance. With the use of commercially available catalyst, the membrane electrode assemblies (MEAs) prepared in this work exhibited a low total-Pt-consumption of 0.064 g kW⁻¹ (stoichiometric ratios of 1.5/2.5 for H₂/air, 80°C, 100 kPa) and achieved the 2025 target proposed by the US Department of Energy. Separating activation, ohmic, and concentration overpotentials, the performance enhancement of the electrospun catalyst layer mainly came from the decrease of ohmic overpotential and concentration overpotential. The electrospun ionomer membrane without catalyst was used as a research model to explore the proton transport properties inside the electrospun catalyst layer. The results showed that in the range of PEMFC operating temperature, the proton conductivity of the electrospun catalyst layer could be higher, but meanwhile the proton-conduction activation energy was also elevated. Compared with the conventional catalyst layer, the electrospun catalyst layer showed obviously better performance before and after accelerated stress test, thus verifying the practicality of the electrospun catalyst layers. This work provided a reference for the development of low platinum and high performance catalyst layers.