Preparation and performance of novel MEA with multi catalyst layer structure for PEFC by magnetron sputter deposition technique

Sputter deposition is widely used for integrated circuit manufacturing and has been investigated for the preparation of more effective fuel cell electrodes for more than a decade. The main problem encountered in this technique is how to increase the contact area. Expanding the two-dimensional thin film structure of the sputter Pt catalyst layer to a three-dimensional reaction zone provides a feasible solution. This study proposes a novel catalyst layer structure composed of multi two-dimensional active layers. This structure is obtained by depositing a Pt layer by magnetron sputter deposition method on a Nafion–carbon ink layer alternatively in order to attain the required three-dimensional reaction zone. SEM, X-ray, EDS and EPMA analysis were used to characterize microstructures, chemical composition and distributions for the obtained electrocatalyst layers. The correlation of microstructures and operation parameters, such as operating pressure and sputtering time, relating to the electrode performance was investigated. The MEAs consist of a Nafion 117 membrane and a commercial electrocatalyst (20% Pt/C from E-TEK) on cathode side. Results show that three layers of Pt sputter-deposited on the gas diffusion layer provides better performance (324.4 mA/cm2 at 0.6 V) than sputtering one Pt layer in the same loading, with an activity of 3244 A/g at 0.6 V for ultra-low loading (0.10 mg/cm2). It demonstrates that the three-dimensional reaction zone causes the effective improvement of performance.