Zhenxing Liang

Pd and Pd-Cu alloy deposited nafion membranes for reduction of methanol crossover in direct methanol fuel cells

Department of Mechanical Engineering, The Hong Kong University of Science and Technology,Clear Water Bay, Kowloon, Hong Kong, ChinaTo reduce methanol crossover in direct methanol fuel cells ~DMFCs!, Nafion 115 membrane was modified by sputtering a thinlayer of Pd or a thin layer of Pd-Cu~60:40! alloy. The sputtered membranes were characterized by using a scanning electronmicroscope, an energy-dispersive X-ray spectrometer, and X-ray diffraction analysis. At room temperature, the modified mem-branes showed significant improvements in both the open-circuit voltage~OCV! and cell performance as compared with the bareNafion 115 membrane; and Pd-sputtered membrane performed better than the Pd-Cu-sputtered membrane in OCV and cellperformance. The methanol permeation rate studied by the voltammetric method in a DMFC configuration under the open-circuitcondition indicated that the improvements in the cell performance occurred because the methanol crossover was lower with themodified membranes than with the bare membrane. At a higher cell operating temperature~70°C!, the Pd-sputtered membraneshowed higher OCV and higher performance only at low current densities, but the performance was found to decline at highcurrent densities. It was also found that at this higher temperature operation, the Pd-Cu-sputtered membrane at high currentdensities exhibited a better performance than the bare Nafion 115 membrane did.© 2005 The Electrochemical Society. @DOI: 10.1149/1.1926671# All rights reserved.Manuscript submitted August 26, 2004; revised manuscript received January 24, 2005. Available electronically June 10, 2005.

FUEL CELLS – DIRECT ALCOHOL FUEL CELLS | Overview

Direct alcohol fuel cells (DAFCs) are a type of electrochemical energy conversion device that directly convert the chemical energy stored in a liquid alcohol fuel, commonly methanol but also ethanol, ethylene glycol, or n-propanol, to electricity. Because of their simplicity, high energy density, instantaneous recharging, and presumably long life, DAFCs have been identified as the most promising candidate to replace batteries in micropower applications. This article presents an overview of DAFC technology, including its working principle, features, challenges, and application opportunities.