Activity and stability tests in phosphotungstic acid electrolyte fuel cell

A 40 cm2 cell based on phosphotungstic acid (PWA) electrolyte has been constructed and tested at the Institute CNR-TAE, Messina. The cell works at room temperature, fed with hydrogen and oxygen as reactant gases. A through-flow design has been used in order to avoid excessive dilution of the electrolytewith water produced in electrochemical reaction. The influence of hydrophobic-hydrophilic characteristics of different electrodes on the activity and stabilityof the cell has been investigated. Pairs of gas diffusion electrodes (cathode and anode), each having the same composition of diffusional and catalytic layer, with 0.50 mgPtcm-2 have been prepared. The pairs differed among themselves for the PTFE loading in the catalyst layer. Each pair of electrodes was tested in the monocell for at least 70 hours under cycling conditions and at current density of 400 mA cm-2. The monocell were conducted with the reagent gases at atmospheric pressure and without external heating. The results of experiments demonstrate that under these conditions the highest monocell activity and stability was obtained with electrodes having 40% of PTFE in the catalyst layer. The activity of the cell having lower PTFE content decreased with time , while the activity of the cell with electrodes having higher PTFE contents increased with time, but did not reach the level of activity of the cell with electrodes having 40% PTFE in catalyst layer.