ChemE Colloquia- SULJO LINIC, University of Michigan
Conversion of solar into chemical energy on plasmonic metal nanostructuresProf. Suljo Linic University of Michigan Department of Chemical Engineering
I will show that composite photo-catalysts combing plasmonic metallic nano-particles of noble metals (Au or Ag) and semiconductor nanostructures (for example TiO2) exhibit an improved photo-chemical activity compared to conventional photo-catalytic materials.[1,2] The critical feature of these composite photo-catalyst is that they couple excellent optical properties of shaped metallic nanostructures (Au or Ag), manifested in the excitation of localized surface plasmons in response to a UV-vis photon flux, and photo-catalytic potential of semiconductors, therefore enabling more efficient conversion of solar flux into electron/hole pairs. The advantage of the composite photo-catalysts will be discussed in the context of photo-catalytic conversion of solar energy into chemical energy of solar fuels by photo-electro-chemical splitting of water to form H2 and O2.
I will also show that plasmonic silver nanoparticles, optically excited with low intensity (order of Solar intensity) visible light, exhibit direct photo-catalytic activity. I will show that the underlying mechanisms governing bond making (breaking) on optically excited plasmonic metals are fundamentally different than on semiconductors and those related to classical thermo-catalytic processes.[2,3] Consequently, plasmonic metals exhibit profoundly different behavior. We have developed a molecular model based on first-principles calculations that describes photo-chemical transformations on plasmonic metals. We show that the model captures the unique, experimentally observed features of the photo-catalytic processes on plasmonic metals. These unique characteristics of plasmonic metallic nanostructures suggest that this new family of photo-catalysts could prove useful for many heterogeneous catalytic processes that cannot be activated using conventional thermal processes on metals or photo-catalytic processes on semiconductors. I will show an example of such a process 
- D. B. Ingram, S. Linic, "Water splitting on composite plasmonic-metal/semiconductor photo-electrodes: Evidence for selective plasmon induced formation of charge carriers near the semiconductor surface", Journal of the American Chemical Society, 133, 5202, 2011
- Suljo Linic, Phillip Christopher and David B. Plasmonic-metal nanostructures for efficient conversion of solar to chemical energy, Nature Materials, 10, 911, 2011.
- Ingram P. Christopher, H. Xin, S. Linic, Visible light enhanced catalytic oxidation reactions on plasmonic silver nanostructures, Nature Chemistry, 3, 467, 2011.
- P. Christopher, H. Xin, M. Andiappan, S. Linic, Singular Characteristics and Unique Chemical Bond Activation Mechanisms of Photocatalytic Reactions on Plasmonic Nanostructures, Nature Materials, 11, 1044, 2012.
- Andiappan Marimuthu, Science, accepted for publication.
Reception at 3:30 PM in 801 Mudd.