Visualization of the oxygen partial pressure in a proton exchange membrane fuel cell during cell operation with low oxygen concentrations

Abstract

The oxygen starvation was investigated in a single-serpentine proton exchange membrane fuel cell (PEMFC) at low oxygen concentrations of 3, 5, and 10% in air. At the voltage lower than 0.6 V, the cell performance abruptly decreased at all oxygen concentrations, but most significantly at 3%. To investigate the processes of the oxygen starvation, the oxygen partial pressure (p(O2)) on the gas diffusion layer (GDL) at low oxygen concentrations (Φ(O2)) of 3, 5, and 10% in air was visualized at the cathode in a running single-serpentine PEMFC by using an oxygen-sensitive dye coated on the GDL. p(O2) continuously lowered in the operating fuel cell along the gas flow channel. At Φ(O2) = 3 and 5% and at oxygen utilizations higher than 90%, p(O2) on the GDL became 0 kPa and susceptible to degradation. The evolution of hydrogen at the cathode was proposed, which might have chemically consumed oxygen near the outlet. Also in a stack, the influence of this hydrogen evolution prior to the hydrogen pumping must be considered.