Effect of Potential-Step Cycling on Corrosion Behavior and Mechanism of Carbon Paper Used in the Gas Diffusion Layer

The durability of gas diffusion layer is critical to the lifetime of proton exchange membrane fuel cells, particularly for the carbon corrosion phenomenon at cathodes caused by the voltage variation during fuel cell operation. Herein, the voltage variation is simulated by a series of potential-step cycling modes to investigate the effect of voltage variation on carbon papers. Carbon paper suffers more severe corrosion with the treatment of potential-step cycling mode than constant potential mode. In addition to the detachment of carbonized resin, corrosion generates two types of oxygen functional groups on surface of carbon paper. More intense carbon corrosion is obtained as the lower potential of the potential-step cycling mode decreases. Physical and electrochemical investigations reveal that it is attributed to the reduction of C–O functional groups on the carbon surface, which passivate carbon surface to prevent corrosion. This work provides new insights into the modification of carbon papers for PEMFCs.