Study of hydrogen peroxide electrosynthesis in electrochemical reactors using amorphous carbon and benzophenone gas diffusion electrode

Author(s)

Taynara Oliveira Silva

• Document type: Doctoral Thesis
• Press: São Carlos.
• Institution: Universidade de São Paulo (USP). Instituto de Química de São Carlos (IQSC/BT)
• Defense date: 2023-09-11

Examining board members

Marcos Roberto de Vasconcelos Lanza; Carla Regina Costa; José Joaquín Linares León; Manuel Andrés Rodrigo Rodrigo; Fernanda de Lourdes Souza

• Advisor: Marcos Roberto de Vasconcelos Lanza

Abstract

The search for new technologies and more efficient catalysts for the electrosynthesis of hydrogen peroxide (H2O2) from the oxygen reduction reaction (ORR) via 2-electron transfer has aroused the interest of numerous researchers, due to the wide range of industrial applications of H2O2. Difficulties in the production of H2O2 from ORR are related to the creation of an effective and low-cost catalyst as well as an electrochemical reactor that optimizes the production of H2O2 on a large scale. The Chapter 1 explored the material of amorphous Printex L6 carbon (PL6C) modified with benzophenone-3,3\',4,4\'-tetracarboxylic dianhydride (BTDA) to be used as cathode matrix for ORR via H2O2 synthesis, electrochemical analyses showed that the modified material reached a satisfactory selectivity value of 97.7%, due to the increase of active sites of the material due to the addition of oxygenated groups in its structure. The modified material PL6C/BTDA 2% was used in the fabrication of gas diffusion electrode (GDE), to employ for the in situ generation of H2O2 and its performance was examined in the Chapter 2, when employing it for the in situ generation of H2O2 values of 275 mg L-1 at 25 mA cm-2 were achieved, when applying this condition for the removal of the endocrine interferent Ciprofloxacin via electrochemical advanced oxidative processes (EOAP), the objective was reached in 20 min with complete degradation of the pollutant. Chapter 3 the optimization of the process and the electrochemical cell used was studied, suggesting a reactor with a new design for the H2O2 generation and also its increase in scale, the arrangement of divided cell collaborated for a greater H2O2 generation; the new proposal of reactor with divided cell reached values of Faradaic efficiency of ~ 90% with EDG PL6C and very satisfactory values of 99.99% with EDG PL6C/BTDA 2%. Chapter 4 presents a possibility, hitherto unexplored, where the in situ H2O2 generated was accumulated in the first 10 min, reaching values of ~112 mg L-1 at 25 mA cm-2, which was sufficient to subsequently, be activated with UVC and used in the degradation of the compound Norfloxacin via EOAP, which took place completely in 10 min.. The achievements discussed in this thesis regarding the electrosynthesis of H2O2 using materials catalysts are likely to contribute to the development of even more efficient H2O2 production systems for degradation of pollutants. (AU)

• FAPESP's process: 19/08701-4 - Hydrogen peroxide electrosynthesis recharging gas thickness electrodes (EDG) modified with combined nanostructured metal oxides
• Grantee: Taynara Oliveira Silva
• Support Opportunities: Scholarships in Brazil - Doctorate (Direct)