A catalytic composite material containing highly conductive Super P carbon black and platinum nanoparticles has been prepared by the liquid-phase synthesis method and studied. An increase in electroactivity of Pt nanoparticles in the presence of highly conductive carbon black has been revealed in comparison with the reference sample, platinized carbon black E-teK, where the carbon material was Vulcan XC-72 carbon black. The nature of the carbon material has been shown to affect the catalytic activity of platinum nanoparticles. The value of the electrochemically active surface area of the developed catalytic material and the catalytic material based on the Etek catalyst has been determined by cyclic voltammetry to be 54 and 20 m 2 /g, respectively.