Mitigating methanol crossover using Pt-Ru catalyst coated on commercial membrane of ethanesulfonyl fluoride through layer-by-layer technique

In this study, 10 bilayers of poly (allylamine hydrochloride) (PAH)/polystyrene sulfonic acid sodium salt (PSS) with Pt-47-Ru-53 catalyst are self-assembled on both sides of the commercial membrane of ethanesulfonyl fluoride via layer-by-layer technique to mitigate methanol crossover. The Pt-47-Ru-53 alloy catalyst is dispersed in the PAH/PSS bi-layers through the reduction of the Pt and Ru ions in the PSS. Experimental results show that the Pt-47-Ru-53 catalyst with an average particle size of 5 nm and a layer thickness of 1.31 mu m, which is similar to the thickness of 10 PAH/PSS bi-layers, is coated onto both sides of the commercial membrane of ethanesulfonyl fluoride. Compared to untreated commercial membrane of ethanesulfonyl fluoride at 60 degrees C, this composite membrane, with Pt-47-Ru-53 loading of 16.5 mu g cm(-2), suppresses methanol crossover by 12% (on average) and improves output voltage and power density by 18% and 46% (@ 79 mA cm(-2)), respectively. The Pt-47-Ru-53 catalyst in the PAH/PSS bi-layers oxidizes the crossed-over methanol and produces extra current. It also reduces the mixed potential effect in the cathode. The 10 PAH/PSS bi-layers with low methanol permeability function like a methanol barrier, blocking the crossed-over methanol. Combining these effects, the self-assembly of the PAH/PSS containing Pt-47-Ru-53 alloy onto the commercial membrane of ethanesulfonyl fluoride can effectively improve output voltage and power density and can suppress methanol crossover. (C) 2013 Elsevier B.V. All rights reserved.