Nano-silica layered composite membranes prepared by PECVD for direct methanol fuel cells

Plasma enhanced chemical vapor deposition (PECVD) technique has been employed to deposit nano-scale films of silica (10, 32, 68 nm) on Nation membrane. Ion conductivity, methanol permeability and single cell performance of the resultant nano-silica/Nafion composite membranes were measured to ascertain its suitability as a candidate membrane for direct methanol fuel cell (DMFC) applications. Experimental results revealed that ion conductivity of the composite membrane containing silica film with 10 nm thickness was similar to the unmodified Nafion membrane, but its methanol permeability was reduced to an extent of 40%. Cell performance of the composite membrane with 10 nm silica was higher than that of the bare Nafion(R) membrane by about 20%. The open circuit voltage (OCV) was increased and the cell temperature at OCV was decreased with an increase in the thickness of the silica film. Physical and electrochemical analyses were conducted to investigate the properties of silica-layered membrane and the DMFC employing the membrane. (C) 2004 Elsevier B.V. All rights reserved.