Effects of pressure modulation on porous gas electrodes

We explore experimentally the coupling between cell voltages at constant current and pressure differentials applied at the gas/electrolyte compartments of a reversible alkaline fuel cell and an electrolyzer system. In the fuel cell mode, higher pressure on the gas side improves the efficiency until gas bubbles evolve into the electrolyte; instead, above a well defined value of overpressure on the electrolyte, the fuel cell voltage drops to zero, as expected. In the electrolyzer mode, an overpressure on the electrolyte decreases the power requirements, mostly due a drop in the overpotential of the H2 electrode. The response of anode and cathode voltages to pressure step consists of a "fast" component and slow "training" or relaxation effects. © The Electrochemical Society.