The structural and electrical characteristics of composite electrodes structurally modified due to the introduction of carbon nanofibers with high porosity and a fraction of transport pores and the formation of the Nafion proton-conducting polymer mainly in island form are studied. The analysis of energy losses for various compositions and optimization of the cathode composition are carried out. The efficiency of the cathode process was increased and the cathode characteristics were improved, the following characteristics of the membrane-electrode assemblies were achieved: at an electrical efficiency of ~ 0.5, the specific loading of platinum was 0.1 g / kW, and the maximum power density was 1 W / cm2.