Formation of CdMoO₄ porous hollow nanospheres via a self-assembly accompanied with Ostwald ripening process and their photocatalytic performance

A simple direct precipitation process in an aqueous solution at room temperature has been developed for the synthesis of monodispersed CdMoO ₄ porous hollow nanospheres (PHNs). The obtained CdMoO₄ PHNs have an average diameter of ∼500 nm and the shell is constructed from nanoparticles with an average diameter of ∼40 nm. The effects of the concentrations of the reaction reagents, pH value and reaction duration have been systematically studied. The formation mechanism of the CdMoO₄ PHNs is related to a self-assembly process accompanied with an Ostwald ripening process, during which the CdMoO₄ solid nanospheres are first formed through the self-assembly of CdMoO₄ nanoparticles and then gradually developed into porous nanospheres with hollow interiors by an Ostwald ripening process. An optical adsorption investigation shows that the CdMoO₄ PHNs exhibit a strong absorption peak in the wavelength of 230-365 nm, centered at 256 nm. The photocatalytic activities of the CdMoO₄ samples for the degradation of Rhodamine B (RhB) under UV light were studied. The CdMoO ₄ PHNs calcined at 300 °C for 2 h exhibit excellent photocatalytic efficiency for the degradation of RhB under UV light, which is up to 97% within 40 minutes. The high photocatalytic performance of the CdMoO ₄ PHNs is associated with the well-crystallized structure and plenty of nanopores which exist in the spheres, serving as transport paths for small molecules.