Electro-generation of hydrogen peroxide using a graphite cathode from exhausted batteries: study of influential parameters on electro-Fenton process

ABSTRACT

In this work, the study of hydrogen peroxide (H₂O₂) electro-generation using graphite from exhausted batteries (Gr-Bat) was conducted. Linear sweep voltammetry and electrolysis experiments were carried out in a single compartment electrochemical cell. Study of the possibility to use this electrode revealed that it presents, as vitreous carbon (VC) electrode, a reduction of oxygen with two successive waves (bi-electronic reduction). The first wave corresponds to the reduction of O₂ to H₂O₂, while the second one corresponds to the reduction of H₂O₂ to H₂O. The cathodic potentials for electro-generation of H₂O₂ appeared at −600 and –700 mV vs. Ag/AgCl for Gr-Bat and VC electrodes, respectively. Subsequently, electrolysis experiments were conducted by imposing the potentials required for H₂O₂ formation. The effect of several operating parameters on H₂O₂ production, such as the nature and concentration of the electrolyte, the pH, the presence of ferrous ions and O₂ injection were studied using Gr-Bat and VC electrodes, respectively. For both electrodes, the acidic medium was more favorable for H₂O₂ electro-generation. The oxygen injection in solution promoted an increase of H₂O₂ concentration, but its effect was more pronounced in the case of VC electrode. Application for crystal violet degradation by electro-Fenton revealed that Gr-Bat had the best purification performance. A removal rate of 73.18% was obtained with Gr-Bat electrode against 62.27% with VC electrode for an electrolysis time of 120 min. This study has demonstrated the possibility of recycling Gr-Bat by using them as cathode materials in the electro-Fenton process.

GRAPHICAL ABSTRACT

KEYWORDS:

• Exhausted batteries
• hydrogen peroxide
• electro-Fenton
• electro-reduction of O₂
• crystal violet

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

This work was supported by the laboratory of electrochemistry and membrane processes of the polytechnic graduate school of Dakar University, Cheikh Anta Diop.