Evaluation for sintering of electrocatalysts and its effect on voltage drops in high-temperature proton exchange membrane fuel cells (HT-PEMFC)

Durability performance such as sintering and voltage drops of HT-PEMFC was theoretically evaluated under non-humid conditions at 150 °C, 170 °C and 190 °C. The quantum chemical molecular dynamics showed that the affinity of the platinum (Pt) electrocatalysts with carbon support decreased with increasing temperature. The degree of agglomeration of electrocatalysts over time simulated by three-dimensional kinetic Monte Carlo method was compared and quantitatively agreed with experimentally measured Transmission Electron Microscopy (TEM) results. Agglomeration of electrocatalysts due to the sintering caused losses of electrochemically active surface area, and found to be occurred more severe as temperature increased. Decreased rate of the proton conductivity due to the evaporation of phosphoric acid affected voltage drops as temperature increased. A theoretical breakdown of the voltage drops indicated that the voltage drops that occurred during the first several hundreds of hours and those occurring for the latter stage were due to different effects.

► Affinity of the electrocatalyst with the support decreased with rising temperature.
► Simulated sintering degree of electrocatalysts became significant as temperature increased.
► Simulated sintered size of electrocatalysts quantitatively agreed with TEM measurements.
► Simulated proton conductivity was found decreased severely with rising temperature.
► Voltage drops over time considering acid loss and sintering agreed with experiments.