Impact of clamping pressure and stress relaxation on the performance of different polymer electrolyte membrane water electrolysis cell designs

One promising option for storing surplus electricity from renewable energy sources is the conversion of electricity to hydrogen by polymer electrolyte membrane (PEM) electrolysis and the subsequent storage of the hydrogen produced. In order to obtain good contact, the components of an electrolysis cell are compressed at a certain clamping pressure. However, too high of a pressure can have a negative effect on cell performance. This work discusses how clamping pressure affects the cell performance of different PEM electrolysis cell designs. A special test cell is designed that makes it possible to apply pressure directly onto the active area of the cell. Polarization curves are measured at different clamping pressures, while electrochemical impedance spectroscopy (EIS) is used to show the effect of pressure on performance losses. Above a critical clamping pressure of 2.5 MPa ohmic losses are found to rise. In addition, it is tested as to whether the clamping pressure remains constant over time. The results show that stress relaxation of the catalyst coated membrane (CCM) leads to a pressure loss and thus to a decline in performance. Therefore, not only is it shown that pressure is crucial for cell performance but also, for the first time, a mechanical effect is described as an element of the cell's degradation. (C) 2019 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.