High-Current Density Durability of Pt/C and PtCo/C Catalysts at Similar Particle Sizes in PEMFCs

The durability of carbon supported PtCo-alloy based nanoparticle catalysts play a key role in the longevity of proton-exchange membrane fuel cells (PEMFC) in electric vehicle applications. To improve its durability, it is important to understand and mitigate the various factors that cause PtCo-based cathode catalyst layers (CCL) to lose performance over time. These factors include i) electrochemical surface area (ECSA) loss, ii) specific activity loss, iii) H+/O-2-transport changes and iv) Co2+ contamination effects. We use a catalyst-specific accelerated stress test (AST) voltage cycling protocol to compare the durability of Pt and PtCo catalysts at similar average nanoparticle size and distribution. Our studies indicate that while Pt and PtCo nanoparticle catalysts suffer from similar magnitudes of electrochemical surface area (ECSA) losses, PtCo catalyst shows a significantly larger cell voltage loss at high current densities upon durability testing. The distinctive factor causing the large cell voltage loss of PtCo catalyst appears to be the secondary effects of the leached Co2+ cations that contaminate the electrode ionomer. A 1D performance model has been used to quantify the cell voltage losses arising from various factors causing degradation of the membrane electrode assembly (MEA).

Automated summary

The durability of carbon supported PtCo-alloy based nanoparticle catalysts is crucial for the longevity of proton-exchange membrane fuel cells in electric vehicle applications. Factors causing performance degradation of PtCo-based cathode catalyst layers over time include ECSA loss, specific activity loss, H+/O-2-transport changes, and Co2+ contamination effects. Accelerated stress test voltage cycling protocol compares the durability of Pt and PtCo catalysts, revealing that PtCo catalysts exhibit larger cell voltage loss at high current densities due to secondary effects of leached Co2+ cations contaminating the electrode ionomer. A 1D performance model quantifies cell voltage losses from various degradation factors of the membrane electrode assembly.