Proton exchange membrane (PEM) technology is considered as very promising for the development of reversible electrochemical cells operating alternatively in water electrolysis and fuel cell modes. Results reported in this communication are related to the development of bi-functional electrocatalytic layers and gas diffusion layers/current collectors for application in reversible PEM cells. In particular, electrodes which do not change their redox function when the mode of operation of the cell is switched (Fig. 1) are more specifically considered.
In order to optimize the composition and structure of the anodic electrocatalytic layer, different bi-functional catalytic mixtures based on nanostructured Pt, Ir and RuxIrySn1-x-yO2 were tested as well as coating processes. Cathodic electrocatalytic layers based on Pt/C and WC were optimized. Special attention was also paid to the design of the gas diffusion electrodes based on bi-porous carbon materials and porous titanium.
The electrochemical performances (current-voltage polarisation curves) of the optimized reversible cells were found to be close to those measured on individual fuel and electrolysis cells with similar membranes and catalyst loadings. For instance, at a current density of 1 A/cm2, typical cell voltages of ca. 1.7 V and 0.7 V were respectively obtained during water electrolysis and H2/O2 fuel cell operation, using Nafion-115 as PEM and noble metal loadings < 1 mg/cm2.
This work has been supported by the Commission of the European Communities (6th Framework Programme, STREP program GenHyPEM n° 019802) and by the “Global Energy” award (research grant for young scientists in the frame of 4th (2007) Russian competition).