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Abstract: Here, we develop a facile electrochemical polymerization method for the synthesis of polypyrrole (PPy) nanowires on Pd modified Nafion® membranes. Interestingly, with altering the deposition potential and temperature, we can easily tune the PPy nanowires from disordered nanostructures to well ordered vertically aligned nanowires. The various PPy nanowires show similar electronic conductivity but diverse hydrophobicity/hydrophilicity. The ordered PPy nanowires can significantly facilitate the mass transport and enhance the catalyst utilization. These two factors together make an obvious performance improvement of fuel cells. [Copyright &y& Elsevier]

Abstract Catalyst poisoning from the impurities in the industrial grade methanol is a major challenge for the large-scale application of direct methanol fuel cells in low cost. In this work, we systematically investigate the impurities influencing on cell performance, and confirm that the adsorption of carbonyl containing intermediate species derived from the partial electro-oxidation of the impurities is a crucial factor leading to performance degradation. Hence, an on-line alleviation strategy by intermittently applying pulse potential (reduction potential on the anode or oxidation potential on the cathode) is proposed. The applied potential will bring a reductive condition on the anode, which releases the active sites via the reduction of carbonyl containing species adsorbed on platinum-ruthenium electro-catalysts. Based on this strategy, the adsorption of carbonyl containing intermediate species are effectively suppressed, and the decay rate declines by nearly two orders of magnitude than that of a single cell under traditional operation, which paves a way for the practical application of direct methanol fuel cells with industrial grade methanol feed. Graphical abstract Image 1 Highlights • Performance/durability of DMFCs with low-cost IG methanol worsen due to impurities. • The effects of impurities on cell performance is systematically investigated. • An electro-reduction route by pulse potential is proposed to recover performance. • Based on the strategy, the decay rate decreased by nearly two orders of magnitude. [ABSTRACT FROM AUTHOR]

Abstract: In this work, an integrated catalyst-coated membrane (CCM) is prepared by successively spray deposit Pt/C nano-suspension, Nafion solution and Pt–Ru/C nano-suspension on a cathode gas diffusion layer using electrohydrodynamic atomization (EHDA) Layer-by-Layer (LbL) deposition. Porous cathode and anode catalyst layers and dense Nafion membrane are deposited using the EHDA LbL deposition technique. It is also found that the EHDA LbL deposited CCM presents close packed structure. An 85 h life test shows that the EHDA LbL deposited cathode electrode side of the integrated CCM still presents well compact feature. Whereas, the delamination of the anode electrode side formed by direct pressing method is evident. The performance of the cell with different methanol concentrations is also examined. It is found that the 3 M methanol concentration gives the highest cell performance. Moreover, the polarization behaviour, methanol crossover and impedance response of the cell at different working temperatures are analysed. The cell performance demonstrates faster increase between 20 °C and 50 °C than between 50 °C and 70 °C. The methanol crossover test shows that the cell presents higher increase level of methanol crossover between 40 °C and 50 °C than other 10 °C temperature increase steps. [Copyright &y& Elsevier]