Influence of anion in sodium salts on photoelectrocatalytic activity of suspended TiO2

Photoelectrocatalytic (PEC) degradation and electrodegradation (ED) of methyl orange were investigated in aqueous NaCl, NaHCO₃ and Na₂SO₄ solutions. The effects of electrolytes concentration and applied potential were studied in the above two processes. Photocatalytic oxidation (PCO) was also performed in TiO₂(P25) suspension under UV-irradiation for comparison. Enhanced decolorization performance could be achieved at higher concentrations of electrolyte solutions and applied potentials for both ED and PEC. There is synergetic effect between electrolysis and photocatalysis treatments. Photocatalytic degradation process alone could result in 51.3% decolorization of methyl orange solution after 60 minutes of irradiation while the degradation rate were 55.1% in 0.5 mol/l NaHCO₃ solution, 68.7% in 0.5 mol/l NaCl solution, and 82.4% in 0.5 mol/l NaH₂PO₄ solution when 2 V bias was applied in photoelectrocatalytic degradation processes.