Does location matter? Hot-electron driven selective photosynthesis of catalytic nanoparticles

It is well known that plasmonic gold nanostructures feature extraordinary capability of absorbing visible light and concentrating the excitation energy in subwavelength volumes. Recently, they have also been proposed as... [ view full abstract ]

It is well known that plasmonic gold nanostructures feature extraordinary capability of absorbing visible light and concentrating the excitation energy in subwavelength volumes. Recently, they have also been proposed as promising candidates for the production of chemical fuels from sunlight. Upon excitation of these nanostructures, the energy is transferred to single electrons that for a brief period of time become highly energetic. Recent scientific advances demonstrate that these highly energetic, “hot” electrons can be extracted and used to drive chemical reactions, such as the conversion of protons to molecular hydrogen. However, to greatly improve the production rate, expensive and rare cocatalysts such as platinum are required.

In order to make effective use of as little catalyst material as possible, it is therefore important to localize the cocatalyst at the places where it is best coupled to the photogenerated hot electrons. To this end, we use the hot electrons themselves to deposit the cocatalyst and to construct photocatalytically active nanostructures. Briefly, a photocathode consisting of ITO-gold nanoislands-TiO₂ was illuminated with red light in presence of PtCl₆, which resulted in the local deposition of platinum nanoparticles on the gold nanoislands. We furthermore compare the photocatalytic performance of these photocathodes, where the platinum nanoparticles were selectively deposited, with those that were fabricated by random-deposition techniques such as electrodeposition and e-beam evaporation.

Overall, these results demonstrate that plasmonic hot electron chemistry can be used for fabricating photocatalytic nanostructures with sub-wavelength control over localization. This careful design of photoelectrodes with nanoscale precision, could open up a new way for higher photocatalytic efficiencies as well as lower fabrication costs.