Compact dynamic hydrogen electrode unit as a reference electrode for PEMFCs

A compact and easy-handling design for the dynamic hydrogen electrode (DHE) was proposed. Before mounting in the cell, a unitized set was made by the hot-pressing of two 2 turn x 5 mm. ionomer membranes, between which two PTFE-coated platinum wires were sandwiched. Before the hot-pressing, a small amount of paste composed of platinum black powder and an ionomer solution was dropped at the end of each wires. Prior to use in a PEMFC, a proper current value for the operation was found in an aqueous acid solution. Mounting of the DHE on a membrane electrode assembly (MEA) was done by local hot-pressing. The space for the mounting was only 2 turn in width between the gasket and edge of the gas diffusion electrode. The potential of the DHE fluctuated, but it was in the range of about 5 mV. A PEMFC with both the DHE and conventional RHE was operated, and the I-V performance of the PEMFC was measured. The potential difference between the conventional RHE and DHE was about 5 mV, which is due to the overpotential of the hydrogen evolution reaction at the DHE. Considering this difference, this DHE is available to monitor single electrode potentials. (c) 2005 Elsevier B.V. All rights reserved.