LAUSR

Abstract An economic low-temperature self-ignition solution combustion method was used to synthesize 1-11 mol% chromium ion (Cr3+) doped MgAl2O4 nanoparticles (NPs). The structural, morphological and energy gap variations due to the influence of Cr3+ on the host matrix was evidenced by powder X-ray diffraction (PXRD), Fourier transformed infrared spectroscopy (FTIR), diffuse reflectance spectroscopy (DRS) and transmission electron microscopy (TEM). Under visible light irradiation, the as-prepared NPs showed excellent photocatalytic activities (PCA) for the industrial dye Acid Red-88 (AR-88) and pyrocatechol (PY) - an emerging pollutant (EP). The experiments were carried out at room temperature in an aqueous solution at a concentration of 20 ppm. Among others, MgAl2O4:Cr3+(5 mol%) showed 91.38% degradation in just 150 min exhibiting a zero-order kinetics and 82% degradation in 6 h displaying the first order kinetics for AR-88 dye and PY EP, respectively. In this, a greater number of hydroxyl (OH.) radicles dominate over other reactive oxygen species (ROS), such as holes and singlet oxygens (1O2) under different pH conditions. Electrochemical studies have yielded the proton diffusion co-efficient (D) value as large as 2.145 × 10-4 cm2s-1 for the optimized NP electrode, substantially greater than 1.0935×10-5 cm2s-1 for the pure MgAl2O4 one owing to intercalated anions and structurally disordered density of the electrode material. This superior electrochemical behaviour suggests potential application of optimized NP material as an anodic electrode for supercapacitors.