Abstract: The electrocatalytic activity of Ti/PbO2 anode for degradation of p-nitrophenol was studied with linear sweeping voltammetry and galvanostatic electrolysis. The electrocatalytic degradation pathway of p-nitrophenol was explored by HPLC analysis of the reaction mixture in the anodic oxidation and cathodic reduction processes. The results indicate that Ti/PbO2 electrode can electrocatalyze the degradation of p-nitrophenol effectively. The conversion of the 1.0 mmol/L p-nitrophenol achieved 98.6% when the electrolysis was carried out for 240 min with a constant current of 40×10-3 A/cm2 at 35 ℃. The pathway of the electrocatalytic oxidation degradation of p-nitrophenol is p-nitrophenol → hydroquinone and pyocatechol → benzoquinone → maleic acid → oxalic acid → CO2 and H2O. The main product of the first step is hydroquinone. The conversions of benzoquinone to maleic acid and maleic acid to oxalic acid are the rate determining steps of anodic oxidation process. The p-nitrophenol can be reduced at the cathode. The reduction products include p-aminophenol. In an electrolytic cell without diaphragm, the cathodic reduction product, p-aminophenol, can be oxidated easily at the anode. The synergsic effect of the cathode and anode speeds up the degradation of p-nitrophenol in an undivided electrolytic cell compared to an electrolytic cell with diaphragm.

Key words: p-nitrophenol, electrocatalysis, degradation, synergsic effect, reaction pathway