Cathodic catalyst layers for proton exchange membrane fuel cells (PEMFCs) are prepared according to a spraying technique and the optimal composition of the catalyst layer is investigated by applying a mixture design approach where the power density of the PEMFC is used as the response of the model Based on the conventional experimental design the optimal Nation content of the electrocatalytic layers of a PEMFC is 35% and a maximum power density (P-max) of 239 5 mW cm(-2) is attained Polytetrafluoroethylene (PTFE) is added to the cathodic catalyst layer to manage water and the relationship between the P-max of the PEMFC (y) and the cathodic pseudo-compositions (Y-1 (Pt/C) Y-2 (Nation) and Y-3 (PTFE)) is obtained y = 204 40Y(1) + 198 60Y(2) + 188 44Y(3) 167 46Y(1) Y-2 (R-2 = 0 9908) Based on the constant power density contours of the cathodic compositions the optimal weight fractions of Pt/C Nation and PTFE are 068 0 29 and 003 respectively and the corresponding P-max is 266 5 mW cm(-2) (C) 2010 Elsevier B V All rights reserved