Insights into the optical and electrochemical features of CuAl2O4 nanoparticles and it use for methyl violet oxidation under sunlight exposure

Herein, the synthesis, optical, and electrochemical characteristics of the spinel CuAl2O4 synthesized by co-precipitation are the focus of this research. As per to the X-ray diffraction (XRD), the obtained sample crystallizes in a cubic symmetry (SG: fd-3m) with a lattice constant of 8.0790 Å. The TEM image revealed spherical nanoparticles with an average build of ∼9 nm and d-spacing of 0.248 nm of the reticular the planes (3 1 1), suggesting the formation of the CuAl2O4 crystalline structure. The optical and dielectric constants, including the extinction coefficient (k), refractive index n (λ), optical conductivity (σopt), dissipation factor (tan δ) and relaxation time (τ) were determined based on diffuse reflectance. The (C−2 - E) graph, plotted in Na2SO4 showed that CuAl2O4, is feature of n-type conduct with a flat band potential of 0.42 VRHE. The EIS spectroscopy displays a semicircle feature with the presence of a constant phase element (CPE) and a bulk resistance of 558 Ω cm2 that lowers to 462.7 Ω cm2 under visible irradiation. As application, the catalytic performance of CuAl2O4 was examined in the breakdown of Methyl violet dye (MV) under sunlight. Within 3 h, an abatement of 89% was obtained, and the oxidation of MV (10 mg/L) follows a first-order kinetic model with a half-life of 82 min. The catalyst can be reused without loss of activity for the first four cycles where •OH and •O2− are accountable of the MV oxidation. [Display omitted] •CuAl2O4 nanoparticles synthesized by co-precipitation and characterized physically and electrochemically.•The diffuse reflectance was used to determine the optical and dielectric constants.•Photo-degradation of Methyl Violet reached 89% within 3 h under solar light.•A mechanism of the photo-degradation has been proposed.