Enhanced photocatalytic efficiency of rGO/NiO nanostructures synthesized using averrhoa bilimbi green extract

The present work aims at an environmentally benign, economically viable, and novel approach for the synthesis of nickel oxide (NiO) nanoparticles (NPs), reduced graphene oxide (rGO), and rGO/NiO nanocomposite (NC) using Averrhoa Bilimbi (A. Bilimbi) fruit extract as a reducing agent. The X-ray diffraction studies (XRD) confirmed the formation of NiO NPs with a face-centered cubic crystalline structure. The average crystallite size of NiO NPs and rGO/NiO NC were estimated to be 26.97 nm and 26.55 nm, respectively. The XRD spectra confirmed the formation of rGO from GO, as evidenced by the appearance of a new peak at 23.33°. Morphology analysis of rGO/NiO NC using a field emission scanning electron microscopy (FESEM) showed the formation of relatively agglomerated, spherically shaped NiO NPs anchored on rGO with an average particle size of 52.72 nm. From UV–Vis-diffuse reflectance spectroscopy (DRS) analysis, the optical energy band gap of rGO/NiO NC was found to be 3.36 eV, which suggested that it can be used as a photocatalyst under UV light irradiation. The photocatalytic study revealed that 30 mg rGO/NiO NC showed excellent photocatalytic activity, completely degrading 5 ppm of methylene blue (MB) dye in 90 min under a UV light source (λ = 254 nm) with an intensity of 9.9975 W/m². Furthermore, the test showcased excellent reusability, making rGO/NiO NC an efficient and stable photocatalyst.