Electrochemical detection and catalytic reduction of nitrobenzene using a bimetallic NiS2/Fe3S4 magnetic heterostructure: an innovative approach for environmental remediation

Nitrobenzene (NB) is a hazardous aromatic compound known for its high environmental persistence and potential toxicity to both human health and ecological systems. The World Health Organization classified NB as a Group 2B carcinogen in 2017. Regular monitoring of NB in water systems remains the primary preventive measure to mitigate the risk of long-term harm to human and animal health. Herein, we report the synthesis of magnetically active NiS2/Fe3S4 nanoflakes for highly selective electrochemical detection and catalytic reduction of nitrobenzene. The NiS2/Fe3S4 nanocomposite was characterised using various techniques such as X-ray diffraction, X-ray photoelectron spectroscopy, scanning electron microscopy, transmission electron microscopy with energy-dispersive spectrometry and elemental mapping, and the NiS2/Fe3S4-modified electrode shows an enhanced electrochemical performance compared to other electrodes. Interestingly, the NiS2 nanospheres are anchored on Fe3S4 nanoflakes, which provides a sufficient pathway for rapid electron/ion transportation. The proposed sensor offers a wide detection range from 0.01 to 100 μM with a correlation coefficient of 0.998 and a very low detection limit of 7.0 nm. Moreover, nitrobenzene is catalytically reduced to the least toxic aniline in the presence of sodium borohydride as a mild reducing agent in just 10 min of contact time. The magnetically separable catalyst offers good recovery, higher stability, selectivity, reproducibility, and real-time monitoring of the contaminants. This work introduces a novel catalyst and a unique approach that combines electrochemical detection and catalytic reduction to efficiently monitor nitrobenzene and to remediate the environment.