Tailoring the ORR selectivity for H2O2 electrogeneration by modification of Printex L6 carbon with 1,4-Naphthoquinone: A theoretical, experimental and environmental application study
H2O2 is one of the most popular precursors used in the production of hydroxyl radical. The compound is employed in advanced oxidative processes (AOPs) for the removal of recalcitrant organic compounds. Amorphous carbon-based matrix is a good oxygen reduction reaction (ORR) catalyst for H2O2 electrogeneration and its modification with electroactive organic compounds can improve ORR efficiency and reduce the energy costs involved in the process. The present work sought to evaluate the electrochemical properties of amorphous carbon-based matrix modified with 1,4-Naphthoquinone (NQE) and its application toward the removal of paracetamol (PRM) in different AOPs. The 1.0 % NQE-modified carbon material showed high selectivity for H2O2 electrogeneration (with 92% of current efficiency), apart from presenting 60 mV displacement of onset potential compared to unmodified carbon matrix. Theoretical studies helped prove that the incorporation of a H+ donor molecule into the catalytic surface improved the ΔG reaction from -277.11 kJ mol-1 for PL6C to -1,222.07 kJ mol-1 for the NQE-modified carbon matrix. Applied at a current density of 75 mA cm-2, modified gas diffusion electrode (GDE) presented a 30% increase in H2O2 electrogeneration compared to unmodified GDE. The study of PRM degradation by the photelectro-Fenton (PEF) process presented the highest removal rate of PRM (~100%), the highest mineralization percentage (42,1%), and the lowest energy consumption (6.35 kWh gTOC-1) in 180 min of experiment. The results show that the technique involving the use of 1.0 % NQE modified carbon matrix for H2O2 electrosynthesis is promising for helps decrease energy consumption, thus contributing toward cost saving in water remediation technology.