Vibrational relaxation dynamics of catalysts on TiO_2 Rutile (110) single crystal surfaces and anatase nanoporous thin films

摘要

Time-resolved vibrational sum frequency generation (VSFG) spectroscopy has been used to investigate the vibrational relaxation dynamics of the rhenium bipyridyl CO_2-reduction catalyst Re(CO)_3Cl(dcbpy) [dcbpy = 4,4'-dicarboxy-2,2'-bipyridine] adsorbed onto the (110) surface of a Rutile TiO_2 single crystal. IR pump-VSFG probe spectra of the a'(1) CO stretching mode indicate a ultrafast population equilibration between three CO stretching modes followed by their population relaxation via intramolecular vibra- tional energy transfer. Similar vibational relaxation dynamics was also observed for the same complex on anatase TiO_2 nanocrystalline thin films measured by IR pump-IR probe transient absorption spectroscopy. The relaxation dynamics of ReCOA on TiO_2, in DMF solution, and immobilized on Au through alkane thiol linkers were compared to examine possible effects of adsorbate-TiO_2 interaction.