The detection and control of free radical antioxidant diphenylamine cations (DPAH + ), a typical organic industrial waste water byproduct, is important for environmental safety and protection. Diphenylamine (DPA) causes severe blood cell damage when it is in contact with living organisms. In this study, we have developed a highly sensitive electrochemical sensor with carbon interlaced nanoflake-assembled Mg x Ni 9−x S 8 microspheres for the detection of diphenylamine. This hybrid electrocatalyst Mg x Ni 9−x S 8 @C material was prepared using a solvothermal co-precipitation method. The microstructural features and elemental composition of the carbon supported Mg x Ni 9−x S 8 microspheres were examined by powder X-ray diffraction (PXRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy dispersive X-ray spectral mapping analysis, and X-ray photoelectron spectroscopy (XPS). The electrochemical performance of the carbon supported Mg x Ni 9−x S 8 microspheres was investigated by cyclic voltammetry (CV) and difference pulse voltammetry (DPV). The carbon supported Mg x Ni 9−x S 8 microspheres exhibit good selectivity, a low detection limit of 16 nM, and wide linear range from 0.1 to 76 μM. This study offers the best platform upon which to explore metal sulfide-carbon matrix microstructures in industrial waste-water treatment as a potential sensing protocol for the detection of DPAH + .