Effect of Oxygen-Free Graphene Sheets on the Rate of Surface Exchange Processes in the Composites Based on Transition Metal Oxides

Currently, nanocomposites based on graphene and transition metal oxides are considered as promising materials for energy accumulation and storage due to their widespread occurrence in nature, low toxicity, and the ability of the metals to change the oxidation state. The rate of surface exchange electrons processes plays an important role in the formation of the electrophysical properties of materials. It is studied an effect of oxygen-free graphene sheets on the activity of nanostructured ceria and zirconia in oxidation–reduction processes, where the rate of surface exchange electron interactions plays a key role. The reaction of CO oxidation is chosen as a model. It is shown that the introduction of oxygen-free graphene sheets up to 3 nm thick into ceria or zirconia nanopowders leads to a decrease in the CO oxidation temperature. Apparently, this effect is caused by the formation of highly active centers with elongated terminal MO bonds in the presence of the sp²-electron system of graphene. It is found that graphene increases the ability of metals to reversible oxygen exchange. The introduction of oxygen-free graphene into the Mn_xO_y/CeO₂ system leads to acceleration of surface exchange processes due to the facilitation of electron transfer in the system as a whole.