Influence of CeO2 loading on the structural, textural, optical and photocatalytic properties of single-pot sol-gel derived ultrafine CeO2/TiO2 nanocomposites for the efficient degradation of tetracycline under visible light irradiation

A single-pot surfactant-free sol-gel method is reported for the facile and bulk synthesis of ultrafine-nanospherical CeO2/TiO2 composites with different CeO2 loadings and their photocatalytic-activity for the degradation and mineralization of tetracycline (TC) under visible-light irradiation is investigated for the first time. The incorporation of CeO2 favored the controlled crystalline growth of TiO2 in its anatase phase, and their crystallinity and particle size were significantly decreased. The textural and optical properties of TiO2 were also improved with the incremental addition of CeO2 by increasing their specific surface-area and visible-light absorption respectively. The optical band gap of TiO2 decreased to 2.24 eV with the incorporation of 1% CeO2 and it further decreased to 2.21 eV with the incremental amount of CeO2. Due to the formation of heterojunction in the composite, the recombination rate of electron-hole pairs was significantly decreased. A highest TC removal efficiency of similar to 99% was observed for 4% CeO2/TiO2 composite for a period of 80 min of visible-light irradiation. Moreover, 88.2% TC mineralization efficiency was achieved for a period of 240 min of visible light irradiation. The enhanced catalytic-activity could be attributed to the synergy of high degree of adsorption followed by an enhanced photocatalysis at the heterointerface formed by the adjacent contact between TiO2 and CeO2. The synergistic effects of low-particle size, high surface-area, enhanced visible-light absorption, reduced band-gap, and increased life-time of the photogenerated charge-carriers through the formation of heterointerface contributed to its high photocatalytic activity. The hydroxyl and superoxide-anion radicals played a superior role in the photocatalytic process. Moreover, the composites retained its efficiency for seven-cycles of reaction without any significant-loss in its activity and structural and textural stability.