Mechanistic insight into the accelerated decay of fuel cells from catalyst-layer structural failure

Abstract

The nonlinear, accelerated decline of fuel cells is a major cause of diminished service life, which is difficult to be detected in early warning. Through in situ electrochemical diagnosis, we found that the accelerated decline of fuel cell could not be directly predicted by the crossover current or the electrochemically active surface area. Surface analysis of catalyst layer showed that the inverse flow of the cathode and anode may lead to dry-wet cyclic stress and corrosion of the catalyst layer in the cathode inlet area (anode outlet area). This leads to cracking in the catalyst layer and corrosion of the carbon support. What’s more, the uncorroded electrolyte will then fill in the original microporous structure, resulting in a decrease in the porosity of the catalyst layer and a corresponding accelerated decline its mass-transfer performance. According to a semi-quantitative model, a 50% corrosion of the catalyst layer leads to a decrease of up to 80% in the equivalent diffusion coefficient, the key mechanism inducing the local performance decline, which leads to accelerated decline of the overall fuel cell performance. This is particularly important for vehicle fuel cells where the local deterioration caused by the uneven distribution of hydrothermal states induces accelerated decline.