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

Sr-doped CuBi 2 O 4 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 CuBi 2 O 4 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 CuBi 2 O 4 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 CuBi 2 O 4 (3.13 %) and about 2.3 times superior than that catalyzed by the untreated Sr–doped CuBi 2 O 4 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 CuBi 2 O 4 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 (O 2 •– ) were the main oxidative species responsible for the photocatalytic degradation of CR dye solution.