Measurement and simulation of voltage differences under ribs and channels and temperature variations within channels in PEMEC

The internal voltage inhomogeneity in a proton exchange membrane electrolyzer cell (PEMEC) is experimentally investigated by using customized gaskets. Three miniature thermocouples are strategically placed inside the channels, specifically in the inlet region, middle region, and outlet region, to monitor temperature variations along the channels. Local voltage measurements are conducted in 13 regions corresponding to the flow channels and 12 regions corresponding to the ribs, under various operating conditions. Additionally, a three-dimensional simulation is performed to analyze the underlying causes of non-uniform voltage distribution and temperature variation. The results reveal contrasting trends in temperature changes along the flow direction, attributable to the varying magnitudes of heat loss and electrochemical heat at different current densities. At low current densities, temperatures increase from the inlet to the outlet along the channels, while at high current densities, temperatures decrease in the same direction. Furthermore, the local voltages of the flow channels (Vchan) and the ribs (Vrib) exhibit different increases along the flow direction at various current densities with the Vchan consistently smaller than Vrib. The inhomogeneity of Vchan is found to be greater than that of Vrib due to bubble disturbances in the channels. The proposed measurement principle for local voltage distribution in PEMECs provides insights into the performance discrepancies between the channel and rib scales in the flow field, thereby enhancing our understanding of electrical property inhomogeneity within the cell.