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 mm × 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 mm 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.