Sulfur-doped NiCr₂O₄ nanocomposites (NCO@g-CNS) ferroelectric, optical and photocatalytic properties: Crystal violet dye degradation under solar light irradiation

Novel sulfur-doped graphitic carbon nitride (g-CNS) nanocomposites with NiCr₂O₄ (NCO@g-CNS) were prepared by coprecipitation and ultrasonication routes. The NCO, g-CNS and NCO@g-CNS1-4 nanocomposites were compared for ferroelectric, optical and photocatalytic properties. P-E loops showed higher charge transfer capabilities due to the incorporation of g-CNS in the NCO structure. SEM analysis confirmed interfacial contact and nanocomposite formation. The optical band gap of NCO (3.18 eV) and g-CNS (2.54 eV) was reduced to 2.68 eV in the case of NCO@g–CNS–4 nanocomposite, which makes the material efficient to carry out the photocatalytic activity under solar light irradiation. The CV dye removal was 92.45 % and 63.72 % for NCO@g–CNS–4 and NCO, with rate constants of 0.01672 min⁻¹ and 0.00922 min⁻¹ within 120 min of irradiation under solar light, respectively. The maximum dye degradation was achieved using a catalyst dose of 20 mg/L and a dye concentration of 15 mg/L at pH 9. Improved photocatalytic efficiency of composites was attributed to e⁻/h⁺ charge separation, which is confirmed by PL analysis. For the investigation of active species in the photocatalytic process, the scavenging experiment was conducted and the results showed that mainly ^•OH radical is responsible for CV dye degradation. The recycling analysis with an 8 % decrease in CV dye degradation after six cycles showed a promising recyclability of the NCO@g–CNS–4 photocatalyst. These findings showed that NCO@g–CNS–4 could have potential for the removal of dyes from the wastewater using solar light, which will make the process cost-effective for practical applications.