| AVS 54th International Symposium | |
| Surface Science | Monday Sessions |
| Session SS1-MoM |
| Session: | Catalysis on Clusters and Nanoparticles |
| Presenter: | J.Y. Park, Lawrence Berkeley National Laboratory and University of California, Berkeley |
| Authors: | J.Y. Park, Lawrence Berkeley National Laboratory and University of California, Berkeley J.R. Renzas, Lawrence Berkeley National Laboratory and University of California, Berkeley B. Hsu, Lawrence Berkeley National Laboratory and University of California, Berkeley Y. Zhang, Lawrence Berkeley National Laboratory and University of California, Berkeley H. Lee., Lawrence Berkeley National Laboratory and University of California, Berkeley P. Yang, Lawrence Berkeley National Laboratory and University of California, Berkeley G.A. Somorjai, Lawrence Berkeley National Laboratory and University of California, Berkeley |
| Correspondent: | Click to Email |
Atomic or molecular processes in metals can generate flows of hot electrons with kinetic energy of 1-3 eV, and mean free path of about 10 nm. The electron flow is detected as a chemicurrent if the excess electron kinetic energy generated by the exothermic reaction is larger than the effective Schottky barrier formed at the metal-semiconductor interface. Detection of hot electron flows could allow us to understand the role of electronic energy dissipation and charge transport through the metal-semiconductor interface in exothermic metal catalyzed reactions. We fabricated nanoparticle-nanodiode hybrid systems composed of metal (Pt and Rh) nanoparticles (size 3-13 nm), an Au thin film (2 nm thick), and TiO2. The interface between Au and TiO2 forms a Schottky barrier with an energy barrier of 1.0 eV. Hot electrons are generated on the surface of the metal nanoparticles, scatter into the Au thin film, and go over the energy barrier between Au and TiO2. The overall thickness of the metal assembly (nanoparticles and Au thin film) is comparable to the electron mean free path, resulting in the ballistic transport of hot electrons through the metal and into the semiconductor. The chemicurrent and chemical reactivity we measured using nanoparticles with sizes of 3-14 nm, and with various capping agents (citrate (trisodium citrate), PVP (polyvinylpyrrolidone), Ctab (tetradecyltrimethylammonium bromide), hexadecylamine, and hexadecylthiol) during catalytic CO oxidation (at pressures of 100 Torr of O2 and 40 Torr of CO at 373 ~513 K). We found that chemicurrent and chemical reactivity depend significantly on the choice of capping layer. While nanoparticles with the citrate capping agent exhibit the highest chemical reactivity and chemicurrent, hexadecylamine, and hexadecylthiol capped nanoparticles shows low reactivity and chemicurrent. We will discuss the size dependence of nanoparticles on the chemicurrent yield. The influence of charging of capping layers on the hot electron transport during the catalytic reaction will be also discussed.