Co-doped V2O5 nanozyme with excellent peroxidase- and oxidase-like activities for efficient degradation of oxytetracycline without an activator

Abstract

Metal oxide nanozymes have shown great promise in degradation of organic pollutants because of their good structural stability, functional versatility and low cost. However, their relatively low catalytic activity restricts their wide applications. This study reports a pathway for synthesis of a Co-doped V₂O₅ nanozyme by introducing histidine and serine-functionalized and boron-doped graphene quantum dots (RSB-GQDs). V⁵⁺ and Co²⁺ were converted into a water-soluble V/Co-RSB-GQD complex via coordination and subsequently annealed to form RSB-GQD@V₂O₅-Co. The introduction of RSB-GQD leads to the formation of small V₂O₅ nanocrystals and rich oxygen vacancies as well as graphene surface modification. Co doping leads to the production of more oxygen vacancies. The integration of RSB-GQDs and Co doping significantly improves electrical conductivity, functional versatility, structural stability and affinity towards oxytetracycline. The V₂O₅-Co in RSB-GQD@V₂O₅-Co exhibits ultra-high oxidase-like activity, showing a specific activity of 125.95 U mg⁻¹ and ultra-high peroxidase-like activity, indicating a specific activity of 893.35 U mg⁻¹. These activities are better than those of choline oxidase and horseradish peroxidase. In the absence of an activator, the degradation efficiency of oxytetracycline reached 97.41% in 5 min, which is more than 3-fold that of only V₂O₅. Such an excellent catalytic behavior can be attributed to the production of multiple active species, including ¹O₂, O₂⁻, ˙OH, and electron holes induced by RSB-GQD@V₂O₅-Co. This study also paves a way for design and synthesis of metal oxide nanozymes with a desirable catalytic performance.