A Segmented Along the Channel PEM Electrolysis Cell for the Operation at High Current Densities

With the improvement of PEM water electrolysis components high performances even at current densities > 7 A/cm² can be reached. Already today it is possible to have cell efficiencies over 60% (referred to thermoneutral voltage) at those high currents with cell voltages < 2.4 V. In the future it is expected to decrease these voltages even more, e.g. by using thinner membranes. At such high current densities, the gas evolution is enormous which could block the access for water to get to the electrode and lead to mass transport limitations (MTL). Especially regarding industrial stack designs with large cell areas, the accumulation along the water-gas channels can course transport and heat management issues. To investigate these phenomena, an along the channel cell was designed. The cell has a width of 2 cm and a length of 30 cm with straight parallel channels. To be able to do locally resolved measurements along the channel the cell is separated into 10 segments without any current connection in between. Thus, electrochemical impedance spectroscopy (EIS) is possible for each segment and the whole cell in parallel. In addition to this, highly resolved measurements of current density and temperature distribution are feasible. The cell was successfully tested up to 10 A/cm² and a differential pressure of 5 bar including EIS during an unsegmented full cell measurement. Figure 1 shows the along-the-channel test cell (left), a polarization curve up to 10 A/cm² (middle) and full cell EIS at high current densities and differential pressure of 5 bar at the cathode and 1 bar at the anode. The future investigations will be to understand the behavior of MTL along the channel under different operation conditions and structural parameters of porous transport layers (PTL). Furthermore, unclear phenomena like the inductive behavior at low frequencies (see figure 1, right) will be investigated.