Synergistic interface engineering in ZnO@CNT catalysts: electronic modulation for switching peroxydisulfate activation toward a 1O2-dominated non-radical pathway

Abstract

Currently, during peroxydisulfate (PDS) activation through Fenton-like reactions, transition metal catalysts face the problem of leaching, whereas carbonaceous materials pose challenges such as difficult recovery, insufficient stability, and less-than-ideal catalytic performance in peroxydisulfate systems. In response to these challenges, the novel composite catalyst (ZnO@CNT) was synthesized through a straightforward one-pot pyrolysis approach. This innovative material exhibits both superior catalytic activity and minimal cytotoxicity, enabling effective activation of peroxodisulfate (PDS) for the degradation of antibiotic sulfamethoxazole (93.56% removal within 30 min kinetic constant: 0.089 min⁻¹). Characterization and density functional theory (DFT) calculations confirmed that the synergistic coupling between ZnO nanoparticles and carbon nanotubes creates abundant active interfaces, thereby enhancing electron transfer and reactive oxygen species generation. Unlike traditional radical-based oxidation systems, mechanistic studies combining electron paramagnetic resonance (EPR) and quenching experiments have identified singlet oxygen (¹O₂) as the primary reactive species, which confers exceptional resistance to complex water matrices containing various interfering substances. Electrochemical analyses provide fundamental insights into the enhanced PDS activation mechanism, demonstrating that ZnO incorporation modulates the electronic structure of CNTs to favor ¹O₂ generation. ZnO@CNT exhibits outstanding cycling stability and environmental safety, as verified by toxicity assessment of transformation products. This work not only develops an efficient metal–carbon hybrid catalyst, but also advances the fundamental understanding of non-radical oxidation pathways for sustainable water purification applications.