A facile one-pot hydrothermal synthesis of two-dimensional TiO2-based nanosheets loaded with surface-enriched NixOy nanoparticles for efficient visible-light-driven photocatalysis

Abstract

Two-dimensional (2D) TiO2-based nanosheets (TNSs) decorated with surface-enriched NixOy (Ni = Ni2+, Ni3+) nanoparticles (Ni-TNSs) were synthesized and found to exhibit a high visible light photocatalytic activity. The thickness and high specific surface area of the Ni-TNSs were measured to be ∼5 nm and 280–350 cm2/g, respectively. Properties, such as the crystal structure, crystallinity, surface area and visible light absorption of the TNSs, were closely associated with the distributed nanoparticles of NixOy (The particle size is less than 2 nm) on the surface. Surface photocurrent, fluorescence spectroscopy, linear sweep voltammetry and Tafel measurements revealed that the separation efficiency of the photogenerated charge carriers can be improved by optimizing the concentration of NixOy (the optimized ratio of Ni/Ti = 3.0 at.%). The photocatalytic degradation of organic pollutants (RhB and MB) under visible light was measured, and the efficiency also strongly depended on the amount of NixOy nanoparticles with an optimal percentage of 3.0 at.%. The photoreactivity of the sample was further studied by determining the formation of photoinduced hydroxyl radicals (OH) by applying coumarin (COU) as a probe material and by obtaining ESR spectra of the superoxide radical adducts (O2−) trapped by DMPO (5,5-dimethyl-1-pyrroline n-oxide). Ten cyclic tests were used to confirm the high stability. A feasible mechanism is described to interpret the enhanced photocatalysis.