Mitigating methanol crossover with self-assembled Pt35–Ru65 catalyst on Nafion surface

Abstract

In this paper, 5 bi-layers of poly (allylamine hydrochloride) (PAH)/polystyrene sulfonic acid sodium salt (PSS) containing Pt35–Ru65 catalyst are self-assembled on the Nafion membrane surface through the layer-by-layer technique to mitigate methanol crossover. This composite Nafion membrane coated with Pt35–Ru65 catalyst with loading of 0.46 μg cm−2 and layer thickness of 87.5 nm on both surfaces suppresses the methanol crossover by 22% (on average), improves the power density by 48% (@0.30 V) and the potential by 22% (@62.5 mA cm−2) at 80 °C. The Pt35–Ru65 catalyst in the PAH/PSS bi-layers serves multiple roles at the same time – a catalytically active layer, a methanol barrier and an electrode. In addition, the PAH/PSS bi-layers also acts as a methanol barrier. These roles contribute to the suppression of methanol crossover and improvement of the output performance. Compared with Pt–Ru directly deposited on Nafion surface, the deposition of Pt35–Ru65 in this study has less negative impact on the cell performance because 1) lesser and thinner deposited Pt35–Ru65 is used, 2) the Pt35–Ru65 layer deposited on the additional PAH/PSS bi-layers does not reduce the proton conductivity of Nafion membrane.