Fe₂O₃/NiO/C nanocomposite synthesis via the coprecipitation method for the photocatalytic degradation of methylene blue dye: synergetic effect

Abstract

• The Fe₂O₃/NiO/carbon nanocomposites were successfully synthesized via a coprecipitation method • The FESEM-EDS image showed a porous morphology and well-scattered elemental distribution. • The nanoscale size of the synthesised materials (10 – 60 nm) was confirmed from the TEM image. • The the development of Fe₂O₃/NiO composites was confirmed from the HRTEM d-spacing analysis. • The nanocomposites catalyst showed an enhanced photocatalysis potential on methylene blue dye. Wastewater generated from textile industries mostly consists of a persistent synthetic organic dye, which has adverse effects on human health and aquatic ecosystems. In this study, the Fe₂O₃/NiO/carbon nanocomposites were synthesized via a coprecipitation method. The source of carbon is from spent coffee grounds. Different molar ratios of precursor salts, Fe(NO₃)₃.9H₂O (0.2M, 0.1M, and 0.2M) and Ni(NO₃)₂.6H₂O (0.2M, 0.2M, and 0.1M), were used. These precursor salts were combined with a constant 0.2 g of carbon coded as (1:1)C, (1:2)C and (2:1)C ratios, respectively. From the XRD pattern analysis, the approximate average crystallite size was found to be 20, 13, and 16 nm for (1:1)C, (1:2)C, and (2:1)C composites, respectively. The porous morphology (BET surface area = 122.826 m²/g), well-scattered elemental distribution, and composition were confirmed from the FESEM-EDS elemental mapping analysis. The approximate particle size obtained from the TEM image is found to be in the range of 10–60 nm. The HRETM image confirmed the composites' formation with d-spacing values of 0.24 and 0.16 nm for Fe₂O₃ and NiO, respectively. The white spots and concentric rings on the SAED ring image confirm the crystalline nature of the materials. FTIR results showed that there was a bending vibration that had to do with the Fe-O and Ni-O bonds. From the PL result, the (1:2)C composite showed the lowest PL intensity compared to (1:1)C and (2:1)C, indicating the presence of greater electron-hole recombination hindrance within (1:2)C heterostructures. The (1:2)C composite also showed the highest methylene blue dye degradation efficiency of 93.35% (k = 0.101 min⁻¹) at the optimized conditions and 30 minutes irradiation time.