Anodic electrocatalytic behavior of graphite supported TiO2 towards the generation of hydroxyl radicals

• TiO2/C anode is used as the electrocatalyst for anodic oxidation. • •OH generation undergoes indirect and direct reaction paths at different potentials. • H2O2 as the intermediate decomposed to •OH indirectly from 1.0 V to 1.2 V. • H2O is oxidized to •OH directly from 1.4 V to 2.0 V. • The direct decomposition of H2O can be inhibited by H2O2 of high concentration. The electrocatalytic mechanism of TiO 2 towards anodic oxidation is mostly described as the electron-hole theory which seems limited and incomplete for its electrocatalytic application. This study focused on the anodic oxidation behavior of graphite supported TiO 2 (TiO 2 /C). The results reveal that the TiO 2 /C anode generates H 2 O 2 as the intermediate which decomposed to •OH indirectly from 1.0 V to 1.2 V. At higher potentials (1.4 V ∼ 2.0 V), the •OH generation is mainly attributed to H 2 O decomposition directly but inhibited by H 2 O 2 in high concentration. The EPR analysis on oxygen defects establishes the relationship between the oxygen defect and the •OH generation experimentally. Together with the in-situ Raman experiments, the mechanisms for the •OH generation on TiO 2 /C anode are further correlated with oxygen vacancy and Ti-OH structure. This study provides a fundamental insight into the electrocatalytic behavior of TiO 2 towards anodic oxidation, which is vital to its application in EAOPs.