Solar-driven photocatalysis of water splitting (to yield hydrogen) and reduction of carbon dioxide (to yield fuels such as CH₄ and CH₃OH) are potentially two of the highest payoff pathways to carbon-neutral fuels. The critical variables limiting the performance of heterogeneous photocatalysis are the inefficient absorption of incident light—especially through the visible region of the solar spectrum—and short lifetimes of photogenerated, reactive electron hole pairs. We have demonstrated that nanostructured titania aerogels with incorporated gold nanoparticles (3D Au–TiO₂) feature (1) Au surface plasmon resonance (SPR)-sensitized photocatalytic activity that spans a broad portion of the visible spectrum, and (2) enhanced electron–hole lifetimes courtesy of the 3D interconnected oxide network. The Au guest is entrained within the 3D network of covalently bonded oxide nanoparticles: configuring Au||TiO₂ interfaces in 3D doubles the rate of visible-light driven photocatalytic water splitting over those produced when Au of the same size and shape is deposited on pre-formed TiO₂ aerogels. Fully exploiting these porous nanostructured materials for photocatalysis requires detailed analysis of the plasmonic sensitization mechanism, identification of nanoscale design parameters that control plasmonic-sensitization efficiency, and understanding the effect of the networked oxide on charge tranport and excited state lifetimes.

In this project, we will exploit the design flexibility of composite aerogels to (1) elucidate the multiple visible-light SPR sensitization mechanisms of TiO₂ by Au that drive solar fuel-producing photocatalysis; (2) use insights derived from (1) to modify the nanoscale design of 3D Au–TiO₂; (3) use 3D networked nanoscale oxides to enhance electron–hole lifetimes; and (4) incorporate the appropriate metal nanoparticles that efficiently catalyze H₂O splitting and CO₂ reduction, separately or in tandem.

References

Panayotov DA, et al: Journal of Physical Chemistry C 117: 15035, 2013

DeSario PA, et al: Nanoscale 5: 8073, 2013