Synthesis and Photoelectrochemical Properties of Copper Titanate for Pollutant Removal

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Copper species are considered one of the materials capable of converting pollutants in add-products values. However, its stability is a challenge when applied in photoelectrocatalytic (PEC) processes. A promissory alternative is to couple copper species with other materials improving their chemical stability, such as TiO2, an p-type semiconductor with excellent charge transfer. The insertion of Cu atoms into the titanium crystal lattice can promote the formation of stable binary copper oxides and/or the production of ternary/quaternary oxides by sharing oxygen between the species1,2. In addition, the presence of TiO2 on CO2 conversion may lead to the reactions for methanol and ethanol formation due to its property to favor the generation of hydroxyl radicals (OH•) and H+ from the oxidation of water. Then, in the present work carried out the preparation of n-type ternary oxide semiconductor based in copper and titanium oxides. Cu–O–Ti was synthesized by a time-efficient, arc-melting method from TiO2 and Cu2O. The particulate product showed in its composition mixture between TiCu2O3 / TiCu3O5 and high crystalline phase. These ternary oxides presented a broad-band absorption in the UV−visible spectral region with absorbance coefficient located at 675 nm. Also, the material showed thermal stability up to ∼475 °C, and cathodic photoelectrochemical activity. Controlled thermal oxidation of copper from the Cu (I) to Cu (II) oxidation state showed that the crystal lattice could accommodate Cu2+ cations up to ∼475 °C, beyond which the compound was converted to CuO and TiCuO3. This process was monitored by powder X-ray diffraction and X-ray photoelectron spectroscopy. The mott-Schottky plots for this ternary oxide exhibited a decrease of capacitance indicating an increase of CO2 absorbing active sites. The efficiency of photocatalyst was evaluated by PEC experiments to CO2 conversion into alcohols. The experiments were carried out bubbling CO2 in 1.0 Mol L-1 NaHCaO3. The ternary oxide favored the ethanol and propane formation, as the final product, exhibiting high selectivity and concentration. Keywords: ternary copper oxide, copper titanate, arc synthesis, p-type semiconductor, photoelectrochemistry, CO2 conversion, C2 products formation.