Redox behavior and electrocatalytic activities of the Ti/nano-TiO2 electrode were investigated by cyclic voltammetry(CV) and bulk electrolysis. The results indicate that there are two pairs of well-defined redox peaks for Ti/nano-TiO2 film electrode in the 1 mol/L H2SO4 and 1 mol/L NaOH at 0.1 V/s corresponding to TiO2/Ti2O3 and T2O3/Ti(OH)(3) reversible electrode process. In 1 mol/L NaOH medium the peak potential evidently shift to the negative value with E-1/2 being -1.38 and -1.72 V (vs. SCE), and the heterogeneous electrocatalytic reduction activities of TiO2/Ti2O3 redox for p-nitrobenzoic acid (PNA) is very high. The indirect electroreduction of PNA to p-aminobenzoic acid (PAA) by Ti-N/Ti-N redox system on nanocrystalline TiO2 film surface was found, and the electrode reaction mechanism is called electrocatalytic(EC) mechanism. In the preparative electrolysis, the current efficiency was over 90%
