A Semi-Empirical Catalyst Degradation Model Based on Voltage Cycling under Automotive Operating Conditions in PEM Fuel Cells

Abstract

Catalyst degradation in membrane electrode assemblies was studied by voltage cycling in hydrogen/air atmosphere. The sensitivity of loss of electrochemically active surface area (ECSA) of the platinum catalyst during voltage cycling to various operating parameters relevant for automotive applications was measured. The investigated stressors were humidity, temperature, upper and lower potential limit and cycle duration. ECSA loss increased at high humidity, temperature and upper potential limit. The impact of the lower potential limit was less pronounced. ECSA loss per cycle increased for longer cycle durations suggesting that the number of cycles and the time spent at high potential in each cycle are of equal importance. A semi-empirical ECSA loss model based on the accelerated stress tests was derived and validated in order to predict platinum surface area loss after voltage cycling and the resulting current-voltage characteristics after degradation.