Synthesis of macroporous ZnO-graphene hybrid monoliths with potential for functional electrodes

The favorable optoelectronic and catalytic properties of zinc oxide, combined with the large specific surface area of graphene molded in 3D network, are able to offer a promising pathway towards the development of hybrid structures with improved electrical, optical, and catalytic properties, that are well suited as active elements for a wide range of applications, especially those related to energy storage and conversion. Using a template-assisted method we demonstrate the synthesis of 3D, porous network monoliths of hybrid ZnO-graphene thin-films in various controlled configurations. The thin-film composites are realized by thermal CVD growth of few-layers graphene on macroporous nickel foam, followed by an ALD coating process of the ZnO film. Notably, the graphene shell fully preserved its network structure after performing complete chemical etching of the nickel scaffold. The challenge of ZnO layer deposition directly on the graphene surface was solved by hydrophobicity adjustment using UV-ozone treatment prior to the atomic layer deposition process. Structural and morphological characterization revealed the formation of hexagonal crystalline zinc oxide films, conformally deposited on the few-layer graphene surface, while the electrical conduction analysis indicates excellent conductivity and interlayer electrical contact for these hybrids. Our results demonstrate that this controlled fabrication process is able to provide highly functional materials with great potential for various electrode applications.