Structure Formation Model in the Pt/C-CNT-Nafion System

Based on the data of electron scanning and transmission microscopy, X-ray energy-dispersive spectroscopy (EDS), voltammetry, and electrochemical impedance spectroscopy the structures of composite electrode materials are modeled. Materials with a mixed (electron and proton) conductivity, which contain platinum nanoparticles on carbon black (Pt/C, electron conductor), the proton-conducting polymer Nafion (fluorocarbon polymer containing sulfo groups), and two types of additives of nanostructured carbon materials (carbon nanotubes (CNTs) and thermally expanded graphite (TEG)) are investigated. Concentration profiles of elements (EDS data) obtained by scanning sample surfaces and features of the dependences of the electrochemically active platinum surface area and concentration dependences of the electron and proton resistance on the Nafion concentration in the material are analyzed. It is shown that the structure of the material, in particular, the proton-conducting polymer Nafion, depends on the type of the additive. Structural models of the materials studied are proposed.