Controllable synthesis of transition metal ion-doped CeO2 micro/nanostructures for improving photocatalytic performance

Ceria (CeO2) micro/nanostructures with various sizes and shapes were successfully synthesized by doping with a series of transition metal ions without any surfactant or template. The crystal structure, morphology, and photocatalytic performance of CeO2 and Co-, Zr-, Cu-doped CeO2 were characterised. The lattice parameters, which indicate the crystal structure distortion and change of Ce4+, were changed by incorporating a transition metal into the CeO2. Doping with transition metal ion could broaden the absorption range from ultraviolet to visible region and enhance the concentration of oxygen vacancies, which exhibited a significantly lower optical band than pure CeO2. The photocatalytic studies revealed that CeO2 with a spate of oxygen vacancies displayed a higher photocatalytic activity than pure CeO2 in degrading the organic pollutant rhodamine B (RhB). Furthermore, the O2− and OH radicals formed during photocatalysis process were revealed by means of nitrotetrazolium blue chloride (NBT) reduction method and a terephthalic acid (TA) fluorescence probe method, respectively, which discovers that radicals were crucial for the degradation of RhB. The H2-TPR confirmed that a small amount of transition metal ions significantly affected the oxidation state of the surface cations and oxygen vacancies. This study clearly reveals the effects of different transition metal ion dopants on the morphologies and photocatalytic performance of transition metal ion-doped CeO2 micro/nanostructures.