Oxygen reduction reaction (ORR)at metal oxide surface is crucially relevant to energy conversion and many aerobic oxidationprocesses.We found that modification of TiO₂ electrode by phosphate or directly immersing the electrode in the phosphate-containing electrolyte speeded up electrochemical reduction of oxygen with enhanced reduction current and decreased overpotential. As a model reaction, during the photocatalytic hydroxylation of aromatics, the O atoms from oxygen became difficult to be introduced into the OH groups of the hydroxyl aromatics in the presence of PO₄^3-, indicating a remarkable change in ORR processes. Through the measurement of H₂O₂ concentration and rotating disc electrode (RDE) test, it wasconfirmed that a four-electron ORR path was induced by phosphate-modification. By the similar eletrochemisty measurements, it was confirmed that other surface-bound proton relays such as L-glumatic acid and malonic acid would have the similar effects to phosphate. However, acetic acid, which could not provide extra acid-base sites after adsorbed on TiO₂ surface, enhanced the ORR current but did not suppressed the formation of H₂O₂. The results have been accepted by Angew. Chem. Int. Ed.(2013, 52, 9686 –9690).