Suppressing methanol crossover with a deposited quaternary Pt-based catalyst on the Nafion surface

Abstract

A Pt49–Ru35–Ir6–Os10 alloy layer is deposited on the Nafion membrane surface using the impregnation-reduction (IR) method to mitigate methanol crossover. The methanol crossover in a membrane electrode assembly (MEA) with a deposited Pt–Ru–Ir–Os layer is compared with a MEA without any layer on the proton exchange membrane (PEM). The deposited Pt49–Ru35–Ir6–Os10 layer functions like a catalytically active layer, a methanol barrier, and an electrode all at the same time. This layer yields up to a 30% suppression of methanol crossover and a 15% improvement in fuel cell voltage performance (@170 mA cm−2) at 80 °C. The porous metal alloy layer with a high surface area of the Pt–Ru layer suppresses methanol crossover by the catalytic activity of the deposited layer. The presence of the solid Pt49–Ru35–Ir6–Os10 layer on the Nafion membrane surface reduces the proton conductivity of the PEM (from 10.75 to 4.22 mS cm−1), and degrades the output of the cell voltage performance (from 0.350 to 0.335 V at 90 mA cm−2 of current density) at 60 °C, even though methanol crossover is reduced (from 6928 ppm to 4415 ppm (CO2 concentration at cathode exhaust is proportional to methanol crossover)).