A bimetallic catalyst of Fe–Co nanocomposite encapsulated in N-doped carbon nanotubes for colorimetric monitoring and degradation of hydroquinone in rivers†

In this study, we developed an encapsulating bimetallic nanoparticle strategy to construct nanocomposites with Fe–Co dual sites inserted into nitrogen-doped carbon nanotubes. The structural composition and morphology of the Fe–Co bimetallic composites were investigated using several characterization methods. The colorimetric assay demonstrated that compared with other composite materials, such as Fe–N–C and Co–N–C, the as-prepared catalyst exhibited improved catalytic performance. DFT calculations of the Gibbs free energy showed that cobalt atoms could synergistically influence the positioning of iron atoms and serve as secondary reaction sites, thereby enhancing the catalytic performance of the composite material. Based on this, a new bimetallic catalyst was fabricated for the colorimetric detection and degradation of hydroquinone. Experimental results showed that the absorbance was linearly correlated with the concentration of HQ in the range of 0.5–30 μM, with a detection limit of 0.21 μM. Besides, the hydroxyl radicals (˙OH) and superoxide anions (O₂˙⁻) generated during the reaction could be utilized to degrade HQ, achieving a removal rate of 85.9% within two hours. Meanwhile, we validated the accuracy of the colorimetric detection of catechol using this catalyst and the HPLC method. In addition, the catalyst was applied to determine HQ in real river water samples, yielding satisfactory results. The work provides a feasible approach for developing low-cost, high-activity and chemically stable bimetallic catalysts for environmental monitoring and protection.