Non-Noble Metal Nickel-Based Catalysts Drive Atomic H*-Mediated Electro-Fenton Process for Highly Efficient Tetracycline Removal: A Breakthrough in Economy and Universality of H

Abstract

The H*-mediated electro-Fenton system, as a novel byproduct-free H2O2 activation technology, faces challenges in economic feasibility and universality. To address these bottlenecks, this study introduced a non-noble nickel-based catalyst as a substitute for the conventionally used precious metal palladium (Pd) and fabricated a sandwich NiO/OCB electrode (SE-NiO/OCB) enriched with three-phase interfaces (TPI) for efficient tetracycline (TC) removal. Through electron spin resonance, electrochemical characterization, and quenching experiments, the SE-NiO/OCB demonstrated efficient catalysis of atomic H* generation, achieving a significantly higher ·OH exposure of 19.18 × 10⁻¹² M·s compared to SE-OCB (5.37 × 10⁻¹² M·s). Additionally, the SE-NiO/OCB exhibited a remarkable TC removal efficiency of 96.7% within 90 minutes, far exceeding SE-OCB (55.9%). Notably, utilizing H+ or H2O as sources for H*, the SE-NiO/OCB maintained a TC removal rate of ≥83.4% across a broad pH range of 3~11, validating exceptional pH adaptability. Additionally, SE-NiO/OCB achieved a removal rate of ≥86.7% for various tetracycline antibiotics at neutral pH, underscoring its broad applicability. The cost of utilizing SE-NiO/OCB to drive the H*-mediated E-Fenton reaction for TC removal was merely 0.05 RMB/(mg TC), which is significantly lower than that of noble metal catalysts. Thus, this study not only provided a fresh insight and a practical approach to addressing the economic and universality concerns of the H*-mediated electro-Fenton system but also proposed an effective strategy for enhancing the treatment of antibiotic-containing wastewater.

Keywords: H*-mediated electro-Fenton, hydroxyl radicals, nickel-based catalyst, sandwich electrode, tetracycline