Facile one-pot synthesis of nickel-incorporated titanium dioxide/graphene oxide composites: Enhancement of photodegradation under visible-irradiation

Highlights: • Ni-incorporated TiO₂/graphene oxide materials were prepared by facile one-pot method. • Raman spectra identified a small fraction of NiTiO₃ at high Ni containing materials. • Graphene oxide acted as adsorption sites and inhibited the agglomeration of Ni particles. • The formation of NiTiO₃ at high Ni content improved photoactivity under visible light. - Abstract: Nickel (Ni)—incorporated titanium dioxide (TiO₂)/graphene oxide composite photocatalysts were prepared by anchoring the TiO₂ and Ni onto the surface of graphene oxide (GO) sheets by a straightforward microwave-assisted, one-pot method for the first time. The as-prepared composite photocatalysts with high Ni content (40–50 wt%) showed good adsorption capacity in the dark and high reaction rate constants under visible illumination while the composite photocatalysts with low Ni content (5–10 wt%) exhibited weak activity. An anatase phase, a small amount of rutile phase and Ni metal were detected using X-ray diffraction (XRD) and transmission electron microscopy (TEM). Raman measurements identified a small fraction of NiTiO₃ only at high Ni content. The formation of NiTiO₃ and the increase in the specific surface area (SSA) for 40 and 50 wt% Ni-loaded catalysts improved the adsorption capacity and photocatalytic activity upon exposure to visible light, resulting in very effective removal of dye contaminants under visible light irradiation. Increasing the Ni content up to 40 and 50 wt% induced not only a structural change affording high porosity but also a narrowing of the band gap to 2.51 eV. Meanwhile, the presence of GO in the composite photocatalysts inhibited the agglomeration of Ni particles even at high Ni content, resulting in similar Ni particle sizes regardless of the Ni content. At the same time, Ni metal accelerated the reduction of the GO sheets, as evidenced by the Raman data.