Cold Startup of a PEFC Studied by Operando Visualization of Ice and Oxygen Partial Pressure

During operation of a polymer electrolyte fuel cell (PEFC) at a subzero temperature, the water generated by the oxygen reduction reaction at the cathode tends to be frozen. During the cold startup test at  −10 °C of a PEFC with five straight channels, the visualization of pO2 on the surface of gas diffusion layer was carried out using an oxygen sensitive dye. During the cooling down of the cell filled with dry nitrogen from 40.5 to −10 °C, the cell resistance increased. The dried mixture gas (N2/O2) supplied at −10 °C increased the cell resistance. During the cold startup, the current density was increased from 2 to 30 mA cm−2. Before the voltage drop, oxygen was found to be consumed near the inlet. The central three channels generated more power than the side two channels.