Tailoring the ORR selectivity for H2O2 electrogeneration by modification of Printex L6 carbon with 1,4-naphthoquinone: a theoretical, experimental and environmental application study

Abstract

The modification of carbon-based materials with electroactive organic compounds can improve the oxygen reduction reaction (ORR) efficiency toward H₂O₂ electrogeneration. The present work sought to evaluate the electrochemical properties of a Printex L6 carbon matrix modified with 1,4-naphthoquinone (NQE) and its application toward the removal of paracetamol in different advanced oxidation processes. The 1.0% NQE-modified material showed 93% selectivity for H₂O₂ electrogeneration compared to 85% for the unmodified carbon matrix. Density functional theory calculations helped confirm the NQE action as an H⁺ donor by improving the ΔG of the reaction from −277.11 kJ mol⁻¹ for PL6C to −986.1 kJ mol⁻¹ for the NQE-modified material. Applied at 75 mA cm⁻², the modified gas diffusion electrode presented a 30% increase in H₂O₂ electrogeneration compared to the unmodified electrode. Paracetamol removal followed pseudo-first-order reaction kinetics in the following order: anodic oxidation with H₂O₂ electrogeneration (AO-H₂O₂) < AO-H₂O₂/UVC < electro-Fenton (EF) < photoelectro-Fenton (PEF). The action of the NQE modifier helped enhance the ORR activity and selectivity for H₂O₂ electrogeneration, thus making the material suitable for environmental application in wastewater treatment.