Solution factors affecting the photocatalytic and photoelectrocatalytic degradation of formic acid using supported TiO2 thin films

The solution factors, i.e. pH of the solution, initial concentration of formic acid (HCOOH),effect of silver ions (Ag(I)) in solution and the mass transfer of HCOOH, affecting the reaction efficiency of the photocatalytic (PC) and photoelectrocatalytic (PEG) degradation of HCOOH were investigated. The maximum PC and PEC (0.3 V vs. saturated calomel electrode (SCE)) degradation of HCOOH occurred at approximately pH 3.4 and no degradation reactions were detected above pH 6. The initial concentration of HCOOH did not affect the reaction rate above 3.8 X 10(-4) M for the PC reaction and above 7.6 X 10(-4) M for the PEC reaction (0.3 V vs. SCE). When Ag(I) was added, it was deposited on the surface of the TiO2 film as metallic silver (Ag(0)) during both reactions. In this case, the degradation rate of HCOOH in both PC and PEC (2 V vs. SCE) reactions decreased. Finally, the mass transfer of HCOOH was shown to be necessary to sustain the PC and PEC reactions.