Performing cyclic voltammetry in a proton exchange membrane fuel cell stack: accessing local electrode properties using current density mapping

Proton exchange membrane fuel cell (PEMFC) electrodes have been extensively studied at multiple levels. As the operation of such system is heterogeneous, several strategies have risen to get insights in local current density. Segmented current collecting plates for single cells or local post mortem analysis for large cells and stacks have been the preferred ways so far to study the local evolution of the electrodes during or after aging studies. Following a previous study on the best practices to carry out cyclic voltammetry (CV) on an individual cell at the stack level, this work introduces a novel use of commercial S++® measurement card, already integrated in stacks to measure local current density in nominal operation (≈ 1–3 A cm−2), for the measurement of local catalyst roughness factors during cyclic voltammograms (≈ 10 mA cm−2). The results show that, independently of the connection configuration used, the S++® card gives global CV measurement overlapping with the one of the potentiostat. However, one shall be careful since the local current density distribution appears to be very dependant of the connection configuration. Single cell polarisation did not enable proper local distribution as it suffered from current redistribution within the bipolar plate facing the S++®. The authors thus introduced and validated here the overlap configuration to obtain trustworthy local current measurements by shifting current collection one cell away from the studied cell. Reliable local CV could therefore be measured by polarising the smallest number of cells as possible (3 cells) instead of the whole stack.