Synergetic effects of Sr-doped CuBi2O4 catalyst with enhanced photoactivity under UVA- light irradiation.

Sr-doped CuBi2O4 micro-particles were successively synthesized via a solid-state technique and were analyzed by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDX), and UV-vis diffuse reflectance spectroscopy (UV-vis-DRS) techniques. Results show that Sr-doped CuBi2O4 was crystallized with a spinel-type structure and tetragonal crystal system, and the band gap energy was about 1.35 eV. The as-prepared Sr-doped CuBi2O4 treated at 573 °C for 12 h exhibited the highest efficiency, as a result of 97.22 % of CR degradation within 220 min, which is approximately 31 times greater than CR photodegradation when catalyzed by CuBi2O4 (3.13 %) and about 2.3 times superior than that catalyzed by the untreated Sr-doped CuBi2O4 sample (42.08 %). Pseudo-first-order kinetic model gave the best fit, with highest correlation coefficients (R (2) = 0.94-0.97). The Sr-doping and extending reaction time up to 12 h could be effective in producing Sr-doped CuBi2O4 materials that delay electron-hole recombination, thereby increasing the lifetime of the electron electron-hole separation and support the charge carrier transfer to the catalyst surface. On the basis of the calculated energy band positions, superoxide radical anions (O2 (•-)) were the main oxidative species responsible for the photocatalytic degradation of CR dye solution.