Title: Hot-Carrier Generation in Quantum-Sized Pt Nanocrystals
Speaker: Dr. Sun Yugang, Temple University
Time: 14:30-15:30p.m., May 23rd, 2017
Venue: Room 105, Shaw Engineering Building, Wushan Campus
Abstract:
Platinum (Pt) nanocrystals are commonly used in chemical reactions because of their unusual catalytic activity, for example, photocatalytic water splitting of water. In a typical design, Pt nanocrystals can accept photo-excited electrons from light absorbers such as semiconductor quantum dots (QDs) to catalyze hydrogen evolution reaction (HER). Charge transfer from QDs to Pt nanocrystals is very inefficient, and shuttle molecules (e.g., methyl viologen) or other shuttle species are necessary to facilitate the charge transfer. In addition to receiving energetic electrons from semiconductor QDs, Pt nanocrystal can also absorb visible light to generate energetic electrons (or hot electrons), which can directly reduce reactive species or migrate across a metal/semiconductor Schottky barrier to the conduction band of a semiconductor. Different from the widely studied plasmonic metal nanocrystals (e.g., Au, Ag), the efficiency of generating hot electrons in the weakly absorbing Pt nanocrystals is very low. We found that depositing Pt nanocrystals on spherical glass beads (i.e., SiO2 particles) could significantly enhance the visible absorption coefficient of the Pt nanocrystals. For example, in SiO2@Pt nanocrystals@TiO2 core-shell nanostructures, the enhancement in visible absorption enables the efficient generation of energetic electrons in photoexcited Pt nanocrystals, which can easily transfer to the TiO2 surface layer to drive HER and many other chemical reactions.
