(Invited) Template Assisted Synthesis of Porous Metal Oxide and Metal Nanostructures by ALD

Abstract

Atomic layer deposition (ALD) has been intensively used to coat porous templates and duplicate the morphology after template removal. Here, we present a systematic investigation on the synthesis of nanoporous Pt and metal oxides via ALD on a sacrificial carbonaceous template: multiwalled carbon nanotubes (MWCNTs).1-3 Pt, Al2O3, TiO2, ZnO and VOx were deposited on MWCNTs, and the samples were subsequently annealed in air to remove the MWCNTs. Scanning electron microscopy (SEM) and high resolution transmission electron microscopy (HRTEM) showed surprising morphological transitions at the nanoscale, while still maintaining the overall forest-type structure at the micro scale. Hollow Al2O3 nanotubes, chains of TiO2 nanoparticles and 3D networks of interconnected V2O5 and ZnO nanoparticles and Pt nanowires were observed after the removal of the MWCNTs templates (see Fig.1). The following photocatalytic test also revealed that the interconnected TiO2 nanoparticle chains showed high catalytic activity towards the degradation of acetaldehyde under UV light. The investigation in the morphological transition in the case of TiO2 nanoparticle chains showed that the crystallization temperature plays an important role in the formation of the final morphology. In the case of 3D network of Pt nanowires, it showed that a continuous coating of metal on the MWCNTs is not indispensable for achieving a self-supported porous structure after template removal. 1S. Deng et al., Nanoscale, 2014, 6, 6939. 2S. Deng et al., J. Mater. Chem. A., 2015, 3, 2642. 3S. Deng et al., RSC Advances, 2014, 4, 11648. Figure 1