Stability of type 310S stainless steel bipolar plates tested at various current densities in proton exchange membrane fuel cells

Type 310S stainless steel bipolar plate is investigated by means of single cell operated at several current densities for 500 h. During the cell operations, the voltage decay is drastic at a lower current density (139 mV at 0 A cm−2), while the fluctuation is mitigated at a higher current density (21 mV at 0.5 A cm−2). The operation results are highly related to the surface conditions of bipolar plates, in particular, the cathode part. At the lower current density, the thickened layer mainly composed of iron oxide layers appears. Meanwhile, the outermost surface is enriched with thin chromium oxide layers when the higher current is applied. It is likely that the thick passive layer on the type 310S stainless steel increases the interfacial contact resistance between the gas diffusion layer and the bipolar plates of the cathode, thereby resulting in progressive voltage decay during the operation. Interestingly, general corrosion is not involved throughout the cell operation, confirming the superiority of type 310S stainless steel under the cell operation environment.