In this work, ozone modification of expanded graphite (EG) was carried out by streaming ozone through a bed of EG. The results of the reaction were evaluated using structural (Brunauer. Emmet and Teller - BET) and surface chemical composition (X-ray photoelectron spectroscopy - XPS) analysis. Electrochemical activity of ozone-treated EG was studied in the model process of phenol electrooxidation in alkaline solutions using cyclic voltammetry (CV). It can be pointed out that the results of EG modification strongly depend on the temperature of the ozone treatment. Indeed, the process carried out at room temperature yielded C=O containing functional groups on the surface, whereas at higher temperatures C-O species were predominantly formed instead, with a simultaneous considerable increase in the specific surface area. Electrochemical studies revealed that phenol electrooxidation was promoted by the EG, ozone-modified at elevated temperatures. (C) 2011 Elsevier B.V. All rights reserved.