Events

Conversion of solar into chemical energy on plasmonic metal nanostructures

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.[4] 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.[4] 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 [5]

1. 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
2. Suljo Linic, Phillip Christopher and David B. Plasmonic-metal nanostructures for efficient conversion of solar to chemical energy, Nature Materials, 10, 911, 2011.
   
3. Ingram P. Christopher, H. Xin, S. Linic, Visible light enhanced catalytic oxidation reactions on plasmonic silver nanostructures, Nature Chemistry, 3, 467, 2011.
   
4. 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.
   
5. Andiappan Marimuthu, Science, accepted for publication.

Reception at 3:30 PM in 801 Mudd.