Cerium and europium doped TiO2 thin films deposited by a sol-gel dip-coating process: characterization and photocatalytic activity toward dye degradation

Abstract

Cerium (Ce) and europium (Eu)-doped $TiO_2$ thin films were obtained by sol-gel dip-coating technique. SEM micrographs showed that the surfaces are covered by agglomerated particles due to the repeating coating process. XRD patterns showed the presence of $TiO_2$ anatase phase. Raman spectra revealed that the peaks recorded at $146 cm^{−1}(Eg )$ and 397 $cm^{−1}(B_{1g})$ were related to the anatase phase. EIS measurements proved that $Ce-TiO_2$ (1wt%) and $Eu-TiO_2$ (0.1wt%) photocatalysts possessed a lower electron transfer resistance than pure $TiO_2$ , which can lead to effective separation of electron/ hole pairs during the photoreactions. The photoactivity of Ce and Eu-doped TiO2 was investigated by the degradation of amido black10B dye (AB) under UV excitation and varying the initial pH and concentrations. It was found that $Eu-TiO_2$ (0.1wt%) exhibited higher photocatalytic activity, reaching a first-order reaction rate of $k_{app} $$(0.036min^{-1}), t_{1/2}$ was around 12 min and AB removal was 98.94%, under optimal pH of 3.5 and AB concentration of 10ppm compared to $(t_{1/2}= 45 min, t_{1/2}=30 min)$, $(k_{app}= 0.022 min^{-1}, k_{app}=0.026min^{-1})$ and AB removal (94.78%, 96.44%), respectively for pure $TiO_2$ and $Ce-TiO_2$ (1wt%). Further increase in Eu/Ce amount up to optimal concentration (1wt% Ce and 0.1wt% Eu) led to a decrease in the AB removal. The mineralization of AB using Eu-$TiO_2$photocatalyst was confirmed by HPLC analysis.