The supported nano-TiO2 electrode was prepared in laboratory, and the photoelectrocatalytic degradation of benzoic acid under UV irradiation was investigated detailedly. The micro-structure and photoelectrocatalytic property of TiO2-film were characterized by scanning electron microscopy, X-ray diffractometry and photo-current response. A value of pH 10.5 was chosen to detect more intermediates generated during the photoelectrocatalytic degradation of benzoic acid by GC/MS. The degradation kinetics, removal yield of total organic carbon, degraded intermediates and the formation of active radical species in different experimental conditions were examined by HPLC, TOC, GC/MS and spin-trap ESR spectrometry. According to above experimental results, the mechanism of benzoic acid photocatalytic degradation was deduced initially. Due to the combined effect of hydroxyl and active oxygen radicals, the hydroxylated benzoic acid, via cis,cis-muconic acid, was decomposed into low molecular weight acid and CO2.

Key words: TiO2 electrode, photoelectrocatalysis, benzoic acid, mineralization, mechanism