Galvanic-like cells produced by negative charge nonuniformity of lattice oxygen on d-TiCuAl–SiO2 nanospheres for enhancement of Fenton-catalytic efficiency

Abstract

An efficient Fenton-type nano-catalyst consisting of Cu, Ti and Al lattice-doped dandelion-like silica nanospheres (d-TiCuAl–SiO₂ Ns) was successfully prepared via a hydrothermal process for the first time. The lattice substitution of Cu, Ti and Al for Si initiated a higher and a lower electron density of the lattice O²⁻ around the lattice Cu and near the lattice Ti & Al, respectively, through the higher electronegativity of Cu on the basis of extended X-ray absorption fine structure, X-ray photoelectron spectroscopy, Fourier-transform infrared spectroscopy, cyclic voltammetry and electron paramagnetic resonance measurement. Thus, countless surface galvanic-like cells formed between the electron-rich Cu center (cathode) and the electron-deficient Ti and Al region (anode) on the nanospheres, enhancing the selective adsorption of H₂O₂ on d-TiCuAl–SiO₂ Ns. This kind of surface structure facilitated the reduction of H₂O₂ to ˙OH at the cathode and induced the oxidation of organic radical intermediates (˙R) on the anode through the delivery of the electron of ˙R to the cathode during the Fenton reaction, which resulted in almost all of the energy of H₂O₂ being applied to the degradation of pollutants. Therefore, d-TiCuAl–SiO₂ Ns were highly effective and stable for persistent contaminant degradation at neutral pH values, which was ∼10 times higher than that of the conventional Fenton catalysts. Moreover, the utilization efficiency of H₂O₂ has been maintained at a very high level throughout the Fenton reaction. Our findings indicated that the special surface design of nanoparticles could be applied toward the improvement of Fenton reaction efficiency and utilization of H₂O₂.