Synthesis of ZnWO4/CdWO4 core–shell structured nanorods formed by an oriented attachment mechanism with enhanced photocatalytic performances

Abstract

ZnWO₄/CdWO₄ core–shell structured nanorods have been synthesized using a simple refluxing method under mild conditions in which the crystallization event of ZnWO₄ happened on the backbone of CdWO₄ single crystalline nanorods in a ligand-free system. A CdWO₄ nanorod-directed oriented attachment mechanism was clearly observed for the formation of the ZnWO₄/CdWO₄ core–shell structured nanorods. The size of the ZnWO₄ could be tuned by changing the molar ratio of the Zn source and the Cd source. The photocatalytic activity of the ZnWO₄/CdWO₄ core–shell structured nanorods was much better than for CdWO₄. The enhancement in photocatalytic performance was demonstrated to be due to the match in lattice and energy levels between the ZnWO₄ and CdWO₄. This match facilitated the separation and transfer of photogenerated e⁻/h⁺ pairs at the heterojunction interfaces and might be important for other heterostructured materials. Kinetic studies using radical scavenger technologies suggested that photogenerated holes were the dominant photooxidants.