In the present work, direct hydroxylation of benzene to phenol by using in situ generated H2O2 with electricity cogeneration was carried out in a proton exchange membrane fuel cell (PEMFC) reactor. Phenol was produced only when there was current through the external circuit. No other organic products were detected during this electrochemical process. A rotating ring-disc electrode (RRDE) technique was used to quantitatively detect the intermediate H2O2 in an acid electrolyte solution at different potentials and temperatures. The RRDE studies showed that the in situ generated H2O2 may play a crucial role during the formation of phenol. The formation rate of phenol could be controlled by adjusting the current or cell potential. (c) 2005 Elsevier B.V. All rights reserved.