Herein, carbon fiber gas diffusion media are replaced by carbon black (CB) and polytetrafluoroethylene (PTFE) composite diffusion media. Uniformly thick monolithic layers are synthesized by a novel die-cast process. They are evaluated for electrical conductivity, contact resistance, hydrophobicity, porosity, and mechanical integrity. Monolithic layers possess combined properties of a microporous layer and gas diffusion layer with a mixed tri-modal pore structure. The monolithic layers are further improved by inducing pores with pore formers. These layers are characterized for use in proton exchange membrane fuel cells. Pore formers increase the porosity and pore volume, and their effects on performance are revealed. The effect of porous structure on catalyst utilization is assessed by cyclic voltammetry. The power density of monolithic layers is on par with standard layers, whereas the pore-induced monolithic layers achieve 27% higher power density compared with standard layers. The synthesized composite gas diffusion media are significantly insensitive to changes in humidity and represent an excellent alternative for use in fuel cells. © 2020 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim