Size-optimized Prussian blue and oxygen-doped carbon nanotubes encapsulation: A catalyst in electro-Fenton for antibiotic degradation

The Electro-Fenton (EF) process has been identified as a potentially effective solution for the treatment of antibiotic wastewater. However, challenges related to catalyst activity and stability persist as significant obstacles. In this study, we developed a bifunctional catalyst that has demonstrated stability in practical applications. A systematic investigation was conducted into the influence of Prussian Blue (PB) particle size (350–950 nm) on Fe³⁺/Fe²⁺ conversion efficiency, and it was identified that 592 nm PB was optimal, achieving the highest conversion rate of 0.162 min⁻¹. To further enhance Fe³⁺/Fe²⁺ cycling, PB was encapsulated within oxidized carbon nanotubes (OCNT), forming an interconnected OCNT/PB catalyst that exhibited a remarkable 204.8 % synergistic enhancement. The superior performance of the catalyst can be attributed to three key factors: (i) The presence of dual active sites for the oxygen reduction reaction (ORR) and Fenton reaction, separated by an atomic-scale distance of 2.352 Å, facilitating both hydrogen peroxide (H₂O₂) generation and its subsequent activation into reactive radicals. (ii) OCNT functioning as an electron-transfer bridge between the cathode and PB, effectively overcoming PB's inherent low conductivity. (iii) Fe complexation on the PB surface with oxygen-containing functional groups, which significantly accelerates Fe³⁺/Fe²⁺ redox cycling. Quantitatively, the coupling of ORR and Fenton sites accounts for 46.6 % of the catalytic activity, the electron-transfer bridge contributes 21.8 %, and Fe complexation enhances activity by 31.5 %. This study offers novel insights into the design of high-performance EF catalysts and presents an innovative strategy for the efficient degradation of organic pollutants in water.