Rapid Crystal Structural, Optical and Morphological Studies of Transition Metal Oxide Nanoparticles and their Photocatalytic Activity

In the present work, we report a green synthesis of cobalt oxide (Co₃O₄), bismuth oxide (Bi₂O₃) and cobalt-doped bismuth oxide (Co-doped BiO) nanoparticles using Bambusa seed extract. The green synthesized nanoparticles are characterized using various techniques such as X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), UV–visible spectroscopy and field emission scanning electron microscopy (FESEM). The phase purity of the synthesized nanoparticles is confirmed with the aid of XRD analysis, and the crystallite sizes are found to be 10.42 nm, 18.85 nm and 61.23 nm for Co₃O_4, Bi₂O₃ and Co-doped BiO nanoparticles, respectively. Bond length calculations and functional group analysis are done by FTIR technique. The UV–visible analysis depicts higher optical absorption and band gaps varying from 1.81, 2.65 and 1.87 eV for Co₃O_4, Bi₂O₃ and Co-doped BiO nanoparticles, respectively. Changes in the surface morphology are observed from FESEM analysis. In addition, the samples' catalytic efficiency in the breakdown of methylene blue (MB) dye was studied and the effects of various process parameters on the extent of dye removals such as photocatalyst amount, irradiation period, the concentration of dye and pH of the solution were also studied. The pseudo-first-order MB photocatalytic decomposition kinetic model has a high correlation coefficient value (R² > 0.95). The findings support the use of a Co-doped BiO in the field of photocatalytic applications under natural sunlight.