Hierarchical yolk-shell WO3 microspheres with highly enhanced photoactivity for selective alcohol oxidations

- Hierarchical WO3 microspheres with yolk-shell structure.
- Enhanced light-harvesting ability via multiple reflections in yolk-shell chambers.
- Photocatalytic selective oxidation of aromatic alcohols in aqueous medium.
- Remarkable photocatalytic reactivity attributed to synergistic promoting effect.

Hierarchical WO3 microspheres with controllable interior structures from solid, yolk-shell, to hollow were synthesized through sonochemical precipitation and hydrogen ion-exchange routes followed by thermal treatment. During the photocatalytic selective oxidation of aromatic alcohols to their corresponding aldehydes in aqueous medium under light irradiation with full wavelengths, the yolk-shell WO3 microspheres exhibited much higher photocatalytic activity than those WO3 microspheres with solid and hollow structures, respectively. This superior activity of the yolk-shell WO3 microspheres can be attributed to the synergistic promoting effect of the following factors: firstly, the porous structure constructed by self-assembly of the interconnected nanosheets together with high surface area promoted the light harvesting and also facilitated the adsorption and diffusion of reactant molecules; secondly, the small crystallite size favored the rapid transfer of photoelectrons, which diminished the transfer distance of photoelectrons and thus inhibited their recombination with holes; thirdly, the yolk-shell structure enhanced light harvesting via multiple reflections in the yolk-shell chambers. Meanwhile, all the WO3 photocatalysts displayed excellent durability against structural collapse due to the robust hierarchical structures. This work identifies the important role of yolk-shell structure played in photocatalytic selective oxidation of aromatic alcohols.

Hierarchical yolk-shell WO3 microspheres were synthesized by hydrothermal method combining hydrogen ion-exchange route, which exhibited remarkable photoactivity in selective alcohol oxidations in aqueous medium owning to the synergistic promoting effect via the porous structure together with high surface area, the small crystallite size, and the enhanced light harvesting via multiple reflections in the yolk-shell chambers.150