Efficient hydroxylation of benzene to phenol by H2O2 using Ni-doped CuWO4 on carbon nitride as a catalyst under solar irradiation and its structure–activity correlation

Abstract

A series of environmentally benign and highly efficient Z-scheme Ni-doped CuWO₄ nanoparticles on graphitic carbon nitride (g-C₃N₄) were synthesized. The Ni-CuWO₄ nanoparticles were prepared via the substitution of Ni²⁺ on a wolframite CuWO₄ crystal. The photocatalytic activity of these nanocomposites was investigated for the hydroxylation of benzene to phenol, considering the importance of phenol and carcinogenicity of benzene. An excellent benzene conversion of 98.5%, with 82.7% selectivity and 81.5% yield of phenol, was achieved over 0.2% Ni-CuWO₄/g-C₃N₄ in 15 minutes under sunlight using H₂O₂ as an oxidant in water, which is higher than those of pristine g-C₃N₄ and Ni-CuWO₄. The high yield of phenol is mainly attributed to the narrow band gap of the semiconductor and enhanced visible light absorption capacity over a specific range of wavelength by the introduction of g-C₃N₄, which minimized the rapid recombination of photogenerated holes and electrons. The computational study related to this work also implied the high optical property and stability of the photocatalyst.