The behavior of supported alloyed and de-alloyed platinum-copper catalysts, which contained 14–27% wt. of Pt, was studied in the reactions of methanol electrooxidation (MOR) and oxygen electroreduction (ORR) in 0.1 M HClO₄ solutions. Alloyed PtCu_x/C catalysts were prepared by a multistage sequential deposition of copper and platinum onto a Vulcan XC72 dispersed carbon support. De-alloyed PtCu_x−y/C catalysts were prepared by PtCu_x/C materials pretreatment in acid solutions. The effects of the catalysts initial composition and the acid treatment condition on their composition, structure, and catalytic activity in MOR and ORR were studied. Functional characteristics of platinum-copper catalysts were compared with those of commercial Pt/C catalysts when tested, both in an electrochemical cell and in H₂/Air membrane-electrode assembly (MEA). It was shown that the acid pretreatment of platinum-copper catalysts practically does not have negative effect on their catalytic activity, but it reduces the amount of copper passing into the solution during the subsequent electrochemical study. The activity of platinum-copper catalysts in the MOR and the current-voltage characteristics of the H₂/Air proton-exchange membrane fuel cell MEAs measured in the process of their life tests were much higher than those of the Pt/C catalysts.

The stability of Nafion–carbon composites is important for the efficient functioning of fuel cells. The thermal decomposition of Nafion, nanostructured carbon materials, such as multi-walled carbon nanotubes, graphene-like materials, and their composites, have been studied using constant heating rate thermogravimetry in air. Materials were characterized by quantitative and qualitative analysis methods, such as thermogravimetry, X-ray photoelectron spectroscopy, scanning, and transmission electron microscopy with field emission. In Nafion–carbon composites, an increase in the thermal stability of the Nafion polymer is observed due to the formation of surface compounds at the Nafion–carbon interface. In this case, the degree of stabilization is affected by both the component composition of the composite and the structure of the nanocarbon material. The greatest effect was obtained in the case of using thermally expanded graphite (few-layer graphene). Nafion is distributed to a greater extent over the surface of the carbon material due to its high structural accessibility. The most thermally stable composite is Nafion–graphene in a mass ratio of components 1:4 with one stage Nafion degradation at 422 °C, whereas the degradation of pristine Nafion occurs in three stages at 341, 413, and 430 °C. The dependences of thermal stability and features of thermal degradation on the composition and structure of composites are discussed.

Compositional proton-conducting membranes based on perfluorinated Aquivion^®-type copolymers modified by detonation nanodiamonds (DND) with positively charged surfaces were prepared to improve the performance of hydrogen fuel cells. Small-angle neutron scattering (SANS) experiments demonstrated the fine structure in such membranes filled with DND (0–5 wt.%), where the conducting channels typical for Aquivion^® membranes are mostly preserved while DND particles (4–5 nm in size) decorated the polymer domains on a submicron scale, according to scanning electron microscopy (SEM) data. With the increase in DND content (0, 0.5, and 2.6 wt.%) the thermogravimetric analysis, potentiometry, potentiodynamic, and potentiotatic curves showed a stabilizing effect of the DNDs on the operational characteristics of the membranes. Membrane–electrode assemblies (MEA), working in the O₂/H₂ system with the membranes of different compositions, demonstrated improved functional properties of the modified membranes, such as larger operational stability, lower proton resistance, and higher current densities at elevated temperatures in the extended temperature range (22–120 °C) compared to pure membranes without additives.