In this paper, 5 bi-layers of poly (allylamine hydrochloride) (PAH)/polystyrene sulfonic acid sodium salt (PSS) containing Pt-35-Ru-65 catalyst are self-assembled on the Nation membrane surface through the layer-by-layer technique to mitigate methanol crossover. This composite Nation membrane coated with Pt35-Ru65 catalyst with loading of 0.46 mu g 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 degrees C. The Pt-35-Ru-65 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 Nation surface, the deposition of Pt-35-Ru-65 in this study has less negative impact on the cell performance because 1) lesser and thinner deposited Pt-35-Ru-65 is used, 2) the Pt-35-Ru-65 layer deposited on the additional PAH/PSS bi-layers does not reduce the proton conductivity of Nafion membrane. (C) 2012 Elsevier B.V. All rights reserved.