High-temperature PEM fuel cell catalysts and catalyst layers

Abstract

High-temperature PEMFCs (i.e., ≥ 90 °C) have several advantages over lowtemperature PEMFCs (i.e., ≤ 90 °C) in terms of reaction kinetics, contaminant tolerance, water management, and heat rejection. However, at high-temperature operation, material degradation is the main challenge. Therefore, development of materials, including catalysts, that are suitable for high-temperature operation is the main task for those working on HT-PEMFCs. To date, the major focus has been upon the degradation of materials in lowtemperature PEMFCs. Research has identified that catalyst degradation occurs primarily in two ways: catalyst sintering/agglomeration and catalyst support oxidation. Catalyst sintering/agglomeration is caused by Pt dissolution/ redeposition, resulting in the growth of Pt particles, and by Pt migration, leading to Pt deposition in membranes and redistribution in the catalyst layer. Carbon support oxidation can result in the detachment of the catalyst particles from the support, reducing Pt utilization. Both catalyst sintering/agglomeration and carbon support oxidation are temperature dependent, and therefore high-temperature operation would lead to more severe catalyst degradation. Little attention has been paid to high-temperature catalyst layer development. Due to the unique characteristics of HT-PEMFCs and the different properties of HT materials, the HT-PEMFC catalyst layer is expected to be more variable in composition than its low-temperature counterpart. The development of high-temperature catalysts/catalyst layers is still in its early stages. This area requires more attention and effort in order to achieve a breakthrough in PEMFC technology and commercialization. © 2008 Springer-Verlag.