Investigation of the visible-light-driven catalytic activity of nickel oxide-doped carbon nanotubes/polyvinylpyrrolidone nanocomposites towards methylene blue dye

Abstract

In this study, multi-wall carbon nanotubes (MWCNTs) were wrapped with polyvinylpyrrolidone (PVP) followed by decoration with nickel oxide (NiO) nanoparticles. The composite ofMWCNTs/PVP exhibited an improved capacity for absorbing visible light in comparison to both pristine PVP and MWCNTs alone. Significantly, the ternary nanocomposite of NiO-doped MWCNTs/PVP demonstrated exceptional light absorption in the visible range (400–650 nm). Regarding XRD results, in the PVP pattern, a broad peak at 2θ = 20° implies its semi-crystalline structure. NiO displays diffraction peaks corresponding to the (111), (200), and (220) planes, verifying its crystallinity. Pure MWCNTs exhibit a strong peak at 2θ = 25.62° for the (002) plane, consistent with graphene structure. The MWCNTs/PVP/NiO sample was confirmed by the existence of characteristic peaks for all three components, which indicates successful formation of the triple nanocomposite. The morphological study by FESEM showed that MWCNTs possess diverse nanotube lengths and diameters with concentric graphene layers. In addition, NiO nanoparticles exhibited a uniform, spherical shape with a nanoscale diameter. Finally, the MWCNTs/PVP/NiO sample showed shorter MWCNTs dispersed in a PVP matrix with incorporated NiO nanoparticles. The photodegradation test revealed that pristine MWCNTs show limited photocatalytic performance, while MWCNTs/PVP and MWCNTs/PVP/NiO notably improve dye degradation. The inclusion of NiO nanoparticles, known for their high surface area and light absorption capacity, led to superior methylene blue degradation, underlining their efficacy as photocatalysts.