A generalized Perry-Newman-Cairns model for performance of a generic catalyst layer (CL) with the Butler-Volmer conversion function is considered. The CL polarization curve, the rate of electrochemical conversion S(x) and the thickness of the conversion domain!, are derived for the cases of ideal transport of ions or feed molecules. In both cases, the CL may work in the low- or high-current regime. In the low-current regime with poor ionic transport, l(*) is given by the Newman's current-independent reaction penetration depth. In the high-current regime, l(*) is inversely proportional to the cell current, regardless of the origin of transport loss. The position and width of the transition region between the low- and high-current branches of the polarization curve are calculated. Based on these results, the features of catalyst layer performance in PEMFC, HT-PEMFC, DMFC and SOFC are discussed. (C) 2010 Elsevier Ltd. All rights reserved.