Browsing by Author "Puello, Esneyder"

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    Photocatalytic degradation of methylene blue by the Anderson-type polyoxomolybdates/TiO2 thin films
    (2018) Diaz Uribe, Carlos E.; Rodríguez, Angie; Utria, Daniela; Vallejo, William; Puello, Esneyder; Zarate, Ximena; Schott Verdugo, Eduardo Enrique
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    Photocatalytic study of TiO2 thin films modified with Anderson-type polyoxometalates (Cr, Co and Ni): Experimental and DFT study
    (2023) Diaz-Uribe, Carlos; Duran, Freider; Vallejo, William; Puello, Esneyder; Zarate, Ximena; Schott, Eduardo
    In this work, three Anderson-type polyoxomolybdates (POMs) with general formula (NH4)6-n[XMo6O24H6]- 6+n where X = Co3+, Cr3+, and Ni2+ were deposited on TiO2 thin films Furthermore, the methylene blue (MB) dye adsorption capacity and photocatalytic degradation were studied. Morphological results show that the POMs/TiO2 films have a more heterogeneous surface in terms of particle size and distribution than bare TiO2 films. Optical characterization indicated that the CrMo6/TiO2 material had the lowest band gap energy with a value of 2.8 eV. The adsorption results show that the maximum percentage of MB adsorption was 37 % for NiMo6/TiO2 while bare TiO2 has only 9.2 %. The MB adsorption on POMs-TiO2 was modeled using and the Freundlich model showed the best fit in all studied films for MB removal. The MB photodegradation values shows this tendency 12 % for bare TiO2, 55 % for NiMo6/TiO2, 73 % for NiMo6/TiO2 and, 83 % for CrMo6/ TiO2. Finally, DFT calculations were performed to characterize the geometry and electronic structure of the all compounds studied in this work, with the aim to explain the observed experimental results.
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    Removal and photocatalytic degradation of methylene blue on ZrO2 thin films modified with Anderson-Polioxometalates (Cr3+, Co3+, Cu2+): An experimental and theoretical study
    (2024) Díaz-Uribe, Carlos; Florez, Jiress; Vallejo, William; Duran, Freider; Puello, Esneyder; Roa, Vanesa; Schott, Eduardo; Zarate, Ximena
    In this work, several ZrO2 thin films modified with Anderson-type polyoxomolybdates (POMs) with general formula (NH4)6-n[XMo6O24H6]-6+n where X = Co3+, Cr3+ and, Cu2+ were prepared. Thin films were characterized through SEM and EDX assay, UV–Vis diffuse reflectance and Fourier Transform Infrared (FTIR) assay. The optical bandgap of ZrO2 thin films was determined to be 3.25 eV, while the modified thin films showed a red shift in the optical activity compared with bare ZrO2 thin films. Methylene Blue (MB) adsorption studies showed that Freundlich isotherm describes properly the experimental data for modified-ZrO2 thin films. Besides, the kinetic results showed the MB adsorption of modified-ZrO2 thin films was superior to bare ZrO2 thin film. The adsorption rate values (K2) of the pseudo-second order model follow these trend ZrO2/CrPOM > ZrO2/CoPOM > ZrO2/CuPOM > ZrO2. The photocatalytic activity of the thin films for MB decomposition under UV and Visible irradiation was studied. Among all the catalysts, the ZrO2 thin films showed the lowest photocatalytic degradation rate kap value (kap = 1.5 × 10−3 min−1), while the best result was obtained for ZrO2/CrPOM thin films (kap = 5.7 × 10−3 min−1) under UV irradiation. Besides, this was the only catalyst efficiently active in MB degradation under visible irradiation, these materials reach 10.4 % after 100 min under visible irradiation. Finally, chemical calculations supported the observed results, by means of TDDFT, EDA analysis, Fukui function and periodic DFT calculations.