Photoelectrocatalytic systems based on electrodes of Ti/TiO2-CuO, NtTiO2-NsCuO, NtTiO2-ZrO2 and GDL-Cu2O applied in a isolated and combined way in the water splitting, dissolved CO2 reduction and, oxidation of organic compounds of petroleum produced water

Author(s)

Juliana Ferreira de Brito

• Document type: Doctoral Thesis
• Press: Araraquara. 2018-08-23.
• Institution: Universidade Estadual Paulista (Unesp). Instituto de Química. Araraquara
• Defense date: 2018-08-10
• Advisor: Maria Valnice Boldrin; Maria Valnice Boldrin

Abstract

The present work investigated semiconductor materials applied in photocatalytic, electrocatalytic and photoelectrocatalytic system with the target to produces CO 2 reduction, water oxidation , oxidation of organic compounds present s in petroleum wastewater and CO 2 reduction concomitant to a n oxidation of organic compounds. In the first part of this work was evaluated the performance of the heterojunction electrodes t itanium dioxide and copper oxide II, in the non - nanostructured form, Ti/TiO 2 - CuO and, in the nanostructured configuration, NtTiO 2 - NsCuO, to promote the photoelectrocatalytic reduction of CO 2 intending methanol and ethanol formation. Employing the Ti/ TiO 2 - CuO in low temperature was possible to obtain 91% of selectivity to methanol , reaching 0 . 30 mmol L - 1 after 2h of reaction. Under room temperature was possible to reach the formation of 0 . 10 mol L - 1 , the same value obtained for the completely nanostructure d NtTiO 2 - CuO. The study with trapper s of the holes photogenerated (efficien t oxidants ) show that the nanostructured system compete s with the concomitant oxidation of the methanol formed, been necessary to separate the holes in this system. In the second part of this work was studied the hybrid reacto ph otoele ctrochemistry/electrochemistry employing electrodes of gas diffusion layer decorated with copper oxide I (GDL - Cu 2 O) and TiO 2 nanotubes decorated with copper oxi de II (NtTiO 2 - CuO) for electrochemistry reduction of CO 2 and water oxidation, respectively. The arrangement of this reactor allowed to perform both reactions simultaneously in compartments separated by protons exchange membrane , obtain 0 . 027 mmol L - 1 of formate , 0 . 020 mmol L - 1 of acetat e and 0 . 050 μmol min - 1 of hydrogen after 24 h of reaction. 98% of faradaic efficiency was obtained for the system irradiated with UV - Vis light, showing be possible to promote the oxidation of organic compounds concomitant t o CO 2 reduction. In third part of the work investigated the efficiency of TiO 2 nanotubes electrodes in systems of photocatalysis , ozonation, photoelectrocatalysis and ozonation coupled to photoelectrocatalysis , when applied in the oxidation of petroleum wastewater. The comparison between the technics showed that the photoelectrocatalytic ozonation reached reduction of 97.6% in color , 99 . 9% in turbid ity , 99 . 2% in in organic carbon , 73 . 5% in C O D , 35 . 3% in the conc entra tion of chlo ride and 96 .0 % in the concentra tion of fluor ide after 2h of reaction . The rema ining compounds in the process were benzaldehyde, benzyl al cohol, octadecane and hexadecane acid detected by GC - MS. In the fourth 18 stage of this work was studied the photoelectrocatalytic system compound by photoanodes of NtTiO 2 - ZrO 2 and the cathode GDL - Cu 2 O to promote the oxidation of benzyl alcohol in the anodic compartment, showed as model molecule , once it was one of the compounds more resistant to the photoelectrocatalytic oxidation of the petroleum wastewater , concomitant to the CO 2 reduction in the cathodic compartment. After 3h of reaction the oxidation of benzyl alcohol reach 68.0% concomitant to the simultane ous generation of 3.75 mmol L - 1 of metha nol and 0.96 mmol L - 1 of ethanol. These results are pioneers and bring a new perspective to the study of oxidation of pollutants concomitant to the reduction of CO 2 in systems with complex samples by photocatalysis or photoelectrocatalysis. (AU)

• FAPESP's process: 13/25343-8 - Simultaneous Oxidation of Organic Compounds in Wastewater Petroleum and Reduction of Dissolved CO2 by Photoelectrocatalysis
• Grantee: Juliana Ferreira de Brito
• Support Opportunities: Scholarships in Brazil - Doctorate