Low Pt Thin Cathode Layer Catalyst Layer by Reactive Spray Deposition Technology

Abstract

National Research Council Canada's Institute for Fuel Cell Innovation, NRC-IFCI, has been developing the Reactive Spray Deposition Technology (RSDT) process to optimize composite electrode layer formation and develop novel electrocatalysts and catalyst layers. The RSDT process provides the means necessary to develop the next generation of thin, low platinum or alloy catalyst layers for PEM MEA's. In order to best manage water distribution, mass transport and conductivity, the structure should be a gradient with controlled porosity and controlled distribution of both platinum and ionomer across the catalyst layer. The RSDT process allows good control of the platinum particle size as they are created directly from metal vapors, which prevents agglomeration in the catalyst layer. Additionally, it has the flexibility to build a gradient layer structure across a very thin film catalyst layer (<1 um). In our design, a platinum sub-layer (100 nm) was deposited directly on a Nafion® 117 membrane as a columnar structure. After the sub-layer, the platinum loading was reduced in a co-deposited layer of Pt-Nafion (ionomer)-carbon with the lowest loading closest to the GDL. The combined loading of both layers was <0.05mg/cm2 Pt with this approach. The manufactured catalyst layer has a performance of 0.65V at 1 A/cm2 with 0.05mg/cm2 Pt loading using pure oxygen .