Microstructure of Electrospray Deposited Catalyst Layers for PEMFC Electrodes

Catalyst layers composed of Pt/C catalyst and NafionR ionomer have been prepared by electrospray deposition and characterized. It is shown that electrospray deposition gives rise to particular properties of the layers, regarding porosity and morphology. A dendritic morphology growth gives rise to enhanced porosity in the meso and macroporous range. The porosity study by means of N2 adsorption isotherm and mercury porosimetry reflects that the ionomer film is better accommodated within the microporous structure of the Pt/C catalyst on electrospray deposited layers, compared with layers deposited by airbrushing. Supporting analysis by thermogravimetry coupled with mass spectrometry appears to show a specific interaction between the ionomer film and the Pt/C catalyst surface. These properties may be responsible for the lower resistivity and enhanced platinum utilization that we have encountered in catalyst layers working in the cathode of PEMFC.