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Abstract: In this paper, we use cyclic voltammetry to investigate the effect of protons on the conductivity and reactivity of TiO2 nanotube array (NTA) electrodes in an aqueous redox system. The H+ ion can change the TiO2 nanotube (anatase phase) surface states for electrons transfer. It can also act as an intermediate state for electron transfer to the acceptor species in the electrolyte surrounding the TiO2. The higher the concentration of H+ ions in the aqueous electrolyte, the easier it is for the electrons transfer from the TiO2 to the electrolyte oxidized species. The reduction is facile, with a similar reduction potential for various acceptor species, but re-oxidation is not possible. It is apparently an electrochemical reduction involving a single-proton transfer and single-electron transfer. Based on this conclusion, an electrode (PB/Au/TiO2 NTAs) was fabricated by means of electrodeposition. The electrode used to detect hydrogen peroxide. The sensitivity of the detector is high, and its the detection limit can be as low as 100nM. [Copyright &y& Elsevier]