Layers composed of catalyst particles of platinum supported on carbon (Pt/C) and ionomer phase (Nafion) have been prepared by electrospray deposition. Some properties are studied, such as morphology; porosity; surface area; thermal decomposition; electroactive area; and single cell testing, relevant to their performance as catalyst layer for proton exchange membrane fuel cell (PEMFC) electrodes. A dendritic morphology is obtained by electrospray deposition, with enhanced meso-and macroporosity. Thermogravimetry analysis shows a specific interaction between Pt/C particles and the ionomer phase involving sulfonic acid groups. The electrochemical active area of Pt/C + Nafion electrosprayed films is larger, till about 30% with the optimized ionomer concentration, compared with films deposited by other common techniques or commercial electrodes. The deposited layers are studied as a cathode in single PEMFC under normalized conditions, showing improved performance due to a lower electric resistance and higher electrochemical active area. These results are explained as a consequence of the optimal mesoporous structure, improved distribution, and interaction of the ionomer film with Pt/C catalyst aggregates. The electrospray deposition may be used to prepare PEMFC catalyst layers with a reduced amount of platinum. (C) 2010 The Electrochemical Society. [DOI: 10.1149/1.3425740] All rights reserved.