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Goddeti, Kalyan C.,Lee, Hyosun,Jeon, Beomjoon,Park, Jeong Young The Royal Society of Chemistry 2018 Chemical communications Vol.54 No.65
<P>A novel three-dimensional catalytic nanodiode composed of a Pt thin film on TiO2 nanotubes was designed for the efficient detection of the flux of hot electrons, or chemicurrent, under hydrogen oxidation. We verify a significant increase in the chemicurrent from the fast transport of electrons across the ordered supporting oxide layer. This study demonstrates the direct detection of hot electrons on well-ordered TiO2 nanotubes during the catalytic reaction.</P>
Photon-Induced Hot Electron Effect on the Catalytic Activity of Ceria-Supported Gold Nanoparticles
Kim, Sun Mi,Lee, Hyosun,Goddeti, Kalyan C.,Kim, Sang Hoon,Park, Jeong Young American Chemical Society 2015 The Journal of Physical Chemistry Part C Vol.119 No.28
<P>The role of charge transfer at the metal–oxide interface is a long-standing issue in surface chemistry and heterogeneous catalysis. Previous studies have shown that the flow of hot electrons crossing metal–oxide interfaces correlates with catalytic activity. In this study, we employed ceria-supported gold nanoparticles to identify a correlation between the catalytic activity of CO oxidation and hot electrons generated via light irradiation. We tuned the size of the Au nanoparticles by changing the discharge voltages used in the arc plasma deposition process, thus allowing us to investigate the influence of Au nanoparticle size on changes in catalytic activity. CO oxidation over the Au/CeO<SUB>X</SUB> catalysts was carried out, and we found that the activity of the Au nanoparticles increased as the size of the nanoparticles decreased, which is associated with the cationic character of the Au nanoparticles, as demonstrated by X-ray photoelectron spectroscopy analysis. We also show that the activity of the Au nanoparticles decreases under light irradiation and that smaller nanoparticles show a higher change of turnover frequency compared with larger ones, presumably due to the mean free path of the hot electrons. From these results, we conclude that the cationic property of the gold species, induced by interaction with the CeO<SUB>2</SUB> support, and the flow of hot electrons generated on the interface during light irradiation are mainly responsible for the change in catalytic activity on the Au nanoparticles.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/jpccck/2015/jpccck.2015.119.issue-28/acs.jpcc.5b03287/production/images/medium/jp-2015-03287g_0007.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/jp5b03287'>ACS Electronic Supporting Info</A></P>
Hot plasmonic electron-driven catalytic reactions on patterned metal-insulator-metal nanostructures
Kim, Sun Mi,Lee, Changhwan,Goddeti, Kalyan C.,Park, Jeong Young Royal Society of Chemistry 2017 Nanoscale Vol.9 No.32
<P>The smart design of plasmonic nanostructures offers a unique capability for the efficient conversion of solar energy into chemical energy by strong interactions with resonant photons through the excitation of surface plasmon resonance, which increases the prospect of using sunlight in environmental and energy applications. Here, we show that the catalytic activity of CO oxidation can be tuned by using new model systems: two-dimensional (2D) arrays of metal-insulator-metal (MIM) plasmonic nanoislands designed to efficiently shuttle hot plasmonic electrons. Hot plasmonic electrons are generated upon the absorption of photons on noble metals, followed by the injection of these hot electrons into the Pt nanoparticles through tunneling or Schottky emission mechanisms, depending on the energy of the hot electrons. We found that these MIM nanostructures exhibit higher catalytic activity (<I>i.e.</I>by 40-110%) under light irradiation, revealing a significant impact on the catalytic activity for CO oxidation. The thickness dependence of the enhancement of catalytic activity on the oxide layers is consistent with the tunneling mechanism of hot electron flows. The results imply that surface plasmon-induced hot electron flows by light absorption significantly influence the catalytic activity of CO oxidation.</P>
Charge transport-driven selective oxidation of graphene
Lee, Y.,Choi, H.,Lee, C.,Lee, H.,Goddeti, K.,Moon, S.,Doh, W.,Baik, J.,Kim, J. S.,Choi, J. Royal Society of Chemistry 2016 Nanoscale Vol.8 No.22
<P>Due to the tunability of the physical, electrical, and optical characteristics of graphene, precisely controlling graphene oxidation is of great importance for potential applications of graphene-based electronics. Here, we demonstrate a facile and precise way for graphene oxidation controlled by photoexcited charge transfer depending on the substrate and bias voltage. It is observed that graphene on TiO2 is easily oxidized under UV-ozone treatment, while graphene on SiO2 remains unchanged. The mechanism for the selective oxidation of graphene on TiO2 is associated with charge transfer from the TiO2 to the graphene. Raman spectra were used to investigate the graphene following applied bias voltages on the graphene/TiO2 diode under UV-ozone exposure. We found that under a reverse bias of 0.6 V on the graphene/TiO2 diode, graphene oxidation was accelerated under UV-ozone exposure, thus confirming the role of charge transfer between the graphene and the TiO2 that results in the selective oxidation of the graphene. The selective oxidation of graphene can be utilized for the precise, nanoscale patterning of the graphene oxide and locally patterned chemical doping, finally leading to the feasibility and expansion of a variety of graphene-based applications.</P>
Cheon, Jae Yeong,Kim, Jong Hun,Kim, Jae Hyung,Goddeti, Kalyan C.,Park, Jeong Young,Joo, Sang Hoon American Chemical Society 2014 JOURNAL OF THE AMERICAN CHEMICAL SOCIETY - Vol.136 No.25
<P>Nanostructured carbon materials doped with a variety of heteroatoms have shown promising electrocatalytic activity in the oxygen reduction reaction (ORR). However, understanding of the working principles that underpin the superior ORR activity observed with doped nanocarbons is still limited to predictions based on theoretical calculations. Herein, we demonstrate, for the first time, that the enhanced ORR activity in doped nanocarbons can be correlated with the variation in their nanoscale work function. A series of doped ordered mesoporous carbons (OMCs) were prepared using N, S, and O as dopants; the triple-doped, N,S,O-OMC displayed superior ORR activity and four-electron selectivity compared to the dual-doped (N,O-OMC and S,O-OMC) and the monodoped (O-OMC) OMCs. Significantly, the work functions of these heteroatom-doped OMCs, measured by Kelvin probe force microscopy, display a strong correlation with the activity and reaction kinetics for the ORR. This unprecedented experimental insight can be used to provide an explanation for the enhanced ORR activity of heteroatom-doped carbon materials.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/jacsat/2014/jacsat.2014.136.issue-25/ja503557x/production/images/medium/ja-2014-03557x_0005.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/ja503557x'>ACS Electronic Supporting Info</A></P>