The precursor Ti(OEt)_4 was prepared by anodic dissolution of metallic titanium in absolute ethanol and direct hydrolysis to prepare nanocrystalline TiO_2 film on titanium electrode (Ti/nano-TiO_2) by a sol-gel process. SEM and XRD were used to characterize the structure of nanocrystalline TiO2 film (anatase, 25 nm) . Redox behavior and electrocatalytic activities of the Ti/nano-TiO_2 electrode were investigated by cyclic voltainmetry (CV) and cyclic osteryoung square wave voltammetry ( COV) and bulk electrolysis. The results indicate that there are two pairs of well-defined redox peaks for Ti/nano-TiO_2 film electrode in 1 mol/L H_2SO_4 with E_(1/2)~r of - 0.53 V and - 0. 92 V (vs. SCE) at 0.05 V·s~(-1) in correspondence with TiO_2/Ti_2O_3 and TiO_2/Ti(OH)_3 reversible electrode process and the heterogeneous electrocatalytic reduction activities of TiO_2/Ti_2O_3 redox in the electrode for maleic acid. It is found that the indirect electroreduction of maleic acid to butane diacid was achieved by Ti~ (IV)/Ti~(III) redox system on the nanocrystalline TiO2 film surface, the electrode reaction mechanism is the called catalytic (EC) mechanism.

Key words: NANOPHASE MATERIALS, TITANIUM DIOXIDE, ELECTRO-CATALYSIS, CYCLOVOLTAMGRAPH, maleic acid, butane diacid, SEM, XRD