Nanoscale transport characteristics and catalyst utilization of vertically aligned carbon nanotube (VACNT) catalyst layers (CLs) are evaluated using a fully statistical modeling approach based on the inherent random nature of the catalyst layer structures for fuel cell applications. Composite morphological structures of the catalyst layers are stochastically modeled with a 95% confidence level, and transport phenomena inside the catalyst layers are simulated using the D3Q19 lattice Boltzmann method (LBM). The effective diffusion coefficient of VACNT catalyst layers is predicted to be higher than that of the conventional catalyst layer, despite a relatively small pore diameter and a low-Knudsen diffusion coefficient. Consequently, the VACNT catalyst layers exhibit improved catalyst utilization compared to the conventional catalyst layers. These statistical results obtained from a series of numerical experiments confirm that the PEFC catalyst layers containing the VACNT catalyst supports can provide more efficient reactant transport, resulting in enhanced catalyst utilization for electrochemical reactions. (C) 2019 Elsevier Inc. All rights reserved.