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| Author(s): |
Paulo Jorge Marques Cordeiro Junior
Total Authors: 1
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| Document type: | Doctoral Thesis |
| Press: | São Carlos. |
| Institution: | Universidade de São Paulo (USP). Instituto de Química de São Carlos (IQSC/BT) |
| Defense date: | 2022-08-04 |
| Examining board members: |
Marcos Roberto de Vasconcelos Lanza;
Joelma Perez;
Manuel Andrés Rodrigo Rodrigo;
Mauro Coelho dos Santos;
Elton Fabiano Sitta
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| Advisor: | Marcos Roberto de Vasconcelos Lanza |
| Abstract | |
The electrosynthesis of hydrogen peroxide (H2O2) from the oxygen reduction reaction (ORR) via 2 electron transfer has been a topic of great interest, mainly in searching for new technologies and efficient catalysts. The present work aims to develop new catalysts based on carbonaceous materials modified with porphyrin compounds and their use in the composition of gas diffusion electrodes (GDE) aiming at the application in the removal of the endocrine disruptor, bisphenol-S. In addition, new GDE-based technology and flow-by electrochemical reactors were developed to produce H2O2 at high concentrations. Different commercial carbonaceous materials to be applied as a cathodic matrix for ORR via production of H2O2 were investigated through hydrodynamic electrochemical assays, and how their chemical and physicochemical properties contribute to the selectivity and catalytic activity. Printex L6 (CP- L6) and Printex XE2B carbons showed the highest selectivity and catalytic activities for the electrosynthesis of H2O2, whose high surface area and the presence of carboxyl-type oxygenated functional groups were the main intrinsic properties responsible for the high performance. Among the different porphyrin compounds studied (Mn, Co, Ni, Cu, and Zn) as modified of CP-L6, the incorporation of 5.0% of Co-Porphyrin in CP-L6 (Co-Porfirina/CP-L6) showed the best results, in which it was possible to maintain the high selectivity of the CP-L6 matrix at 90.0% and improve the RRO activity by 72.6%. This better performance was mainly attributed to the π-π electronic interactions between the cobalt metallic center and the active sites present in the CP-L6 matrix, which cause an electrocatalytic effect on the electrosynthesis of H2O2. The GDE modified with Co-Porphyrin/CP-L6 led to an electrogeneration of H2O2 of 333 mg L-1 at the potential of -1.50 V vs Ag/AgCl and allowed a mineralization of BPS by 80% with an energy consumption of 6.3 kWh kg-1 in 360 min via photo electro-Fenton (FEF) process. The remaining organic matter was identified as short-chain carboxylic acids, proving the high efficiency of the FEF process in removing bisphenol-S. Finally, the technology based on CP-L6TC/GDE developed and applied in flow-by electrochemical reactors, allowed obtaining an H2O2 production of 4.6 g L-1 in 12 hours at a current density of 75 mA cm- 2, when operated at the optimum conditions of temperature, O2 gas flow (50 mL min-1) and PTFE percentage (20%). It is expected that the advances described in this thesis, regarding the electrosynthesis of H2O2 from ORR using efficient catalysts based on modified carbonaceous materials, will contribute to the development of H2O2 production systems or even more efficient catalysts. (AU) | |
| FAPESP's process: | 16/19612-4 - Degradation of endocrine disruptors carbofuran, methylparaben and propylparaben via electrogenerated H2O2 and associated processes (electrogenerated H2O2/UV, electro-Fenton e photoelectro-Fenton) |
| Grantee: | Paulo Jorge Marques Cordeiro Junior |
| Support Opportunities: | Scholarships in Brazil - Doctorate (Direct) |