Architectural Processes and Physicochemical Properties of CoO/ZnO and Zn_1−xCo_xO/Co_1−yZn_yO Nanocomposites

In this work we synthesized two inverse kinds of cobalt and zinc oxide nanocomposites (CoO/ZnO and Zn 1− x Co x O/Co 1− y Zn y O) and compared methodologistic features observed from the syntheses. The binary oxide system chosen herein is because divalent cobalt and zinc have very similar ion radii, and they interdiffuse easily when forming doped structures. A “two-pot” process was devised for the CoO/ZnO composites, in which mesocrystalline cores of CoO were formed first, followed by introduction of an overlayer of ZnO nanoparticles to the core surfaces. In contrast, a “one-pot” process was developed for the Zn 1− x Co x O/Co 1− y Zn y O composites. In particular, hollow and/or multishelled Zn 1− x Co x O cores (in wurtzite phase) serve as a support for the nanospheres of Co 1− y Zn y O (in rock-salt phase) in this latter method. Our findings indicate that while “multi-pot” synthesis is a prevailing methodology for composite nanoparticles, simpler “one-pot” synthesis can be an effective approach for preparation of more complex nanocomposite materials, especially for interdoped metal oxides. As an example, our as-prepared binary oxide composites Zn 1− x Co x O/Co 1− y Zn y O have shown good catalytic activity for oxidation of carbon monoxide at relatively low reaction temperatures.