Surface Coating with Porous Zirconia Layers Prepared By Atomic Layer Deposition for Stabilizing Fuel Cell Catalysts

Abstract

Many automakers have recently developed and commercialized electric vehicles that operate on polymer electrolyte membrane fuel cells (PEMFCs). The most important component in PEMFCs is the platinum catalyst. Fuel cell electric vehicles are expected to be particularly useful for heavy-duty cars including buses and trucks that operate at relatively high power for a relatively long-term per charge. Under these operating conditions, it is important to minimize aggregation of platinum (Pt) catalysts that tend to agglomerate in long-term high current (or high power) conditions. In this study, we propose the surface coating of zirconia (ZrO2) using atomic layer deposition (ALD) to prevent the aggregation of fuel cell catalysts. ALD is the most advanced technology for thin film deposition because it can control thickness and composition at the atomic scale. Another advantage of ALD is conformal coating along the surface of complex 3D features. With these unique properties, ALD has successfully demonstrated uniform surface coatings on nanoparticles. One cycle of ALD is generally less than 0.1 nm in many cases, which can in principle form a porous film. We selected ZrO2 as a coating material because of its high thermal and phase stability. As a result, we have succeeded in uniformly depositing ALD ZrO2 as a porous film on the surface of the nano-size metal catalyst, and confirmed that it is truly effective in preventing agglomeration of catalysts in a long-term fuel cell operation.