A Comprehensive Model for Carbon Corrosion during Fuel Cell Start-Up

A transient 1+1 D model has been developed for carbon corrosion during fuel cell start-up. The model considers the species transport in the anode channel and catalyst layer, the double-layer and pseudo capacitances, and the multiple species coverage on carbon and Pt which influences reaction kinetics. Model simulations and analysis have been performed focusing on the reaction kinetics including carbon corrosion rate, the contributions from double-layer and pseudo capacitances, and the effects of initial Pt state at anode and cathode, temperature, and anode O 2 diffusivity. It has been found that the remaining O 2 amount in the anode catalyst layer, rather than the H 2 front, is the key factor for cathode carbon corrosion rate. There exists a charge balance in anode oxygen reduction reaction (ORR) which is the driver for cathode carbon corrosion, cathode oxygen evolution reaction (OER), cathode carbon corrosion reaction (COR), and multiple capacitive currents. Among all capacitive currents, cathode pseudo capacitance contributes most to the protons for anode ORR. Enhancing cathode OER is preferred over cathode pseudo capacitance to reduce COR since the latter approach can increase cathode PtO coverage and Pt dissolution. Higher cathode initial bare Pt surface leads to less cathode carbon corrosion, whereas higher anode initial bare Pt surface enhances anode ORR rate as well as cathode carbon corrosion in the beginning but reduces both afterwards due to faster consumption of the remaining O 2 . Both reduced temperature and anode O 2 diffusivity are shown to decrease the cathode carbon corrosion during start-up, the former being highly effective.