Advanced Fe-doped carbon xerogels as bifunctional electro-catalysts for targeted hydroxyl radical production and superior electro-Fenton pollutant removal in water

Abstract

Bifunctional catalysts for H2O2 production via oxygen reduction reaction (ORR) and OH• generation via Fenton reaction are fundamental for the development and optimization of Electro-Fenton technology. In this context, Fe- doped carbon xerogels have been synthesized by sol-gel polymerization under hydrothermal conditions, which allowed the efficient encapsulation of iron nanoparticles (Fe3C-type crystalline species) within the carbon matrix. This strategy enabled control over the selectivity of the materials towards a three-electron pathway, favoring the direct production of hydroxyl radicals (OH•). Moreover, a good balance between graphitization degree and micro-mesoporous structure resulted in high electrochemical performance in ORR, reaching a kinetic current density as high as 11.56 mA/cm2 at −0.45 V and 32.66 mA/cm2 at −0.80 V. This remarkable performance was reflected in Electro-Fenton experiments, achieving 94% degradation of tetracycline after 8 h, demonstrating the bifunctional effectiveness of the synthesized catalysts.