Evaluation of Silver-coated Magnesium Bipolar Plate for Lightweight PEM Fuel Cell Stack

Abstract

A magnesium bipolar plate whose surface was protected by a thinly deposited silver layer was investigated as an alternative to the existing graphite bipolar plate of polymer electrolyte membrane(PEM) fuel cells. A thin silver layer was deposited on a magnesium alloy substrate by physical vapor deposition at 180℃. A number of tests were conducted on the fabricated magnesium-based bipolar plates to determine their suitability for use in PEM fuel cell stacks. A test on corrosion resistance under the same pH conditions as those in a PEM operation demonstrated that the silver layer protected the magnesium alloy substrate, while an unprotected substrate suffered from severe corrosion. The contact resistance of the fabricated bipolar plate was less than 20 mΩ-cm², which was superior to conventional bipolar plates. A single-cell was constructed using the fabricated bipolar plates and its power output was measured. Owing to the enhanced conductivity caused by low contact resistance, a slight increase was observed in the current density and output voltage. Based on the low density of the magnesium substrate and magnesium’s easy machinability, a weight reduction of 30- 40% is possible for the stack while producing the same power output.

Keywords:

• Polymer Electrolyte Membrane Fuel Cells
• Silver-coated Magnesium Bipolar Plate
• Corrosion Resistance
• Contact Resistance
• Sputtering

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ACKNOWLEDEMENT

This study was conducted with financial assistance from the Korea Government (Department of Education & Science &Technology, Grant No. R0A-2007-000-20065-0)