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Unprecedented Insulator-to-Metal Transition Dynamics by Heterogeneous Catalysis in Pd-Sensitized Single Vanadium Oxide Nanowires

  • Byon, Ji Won (School of Mechanical and Advanced Materials Engineering, KIST-UNIST-Ulsan Center for Convergent Materials, Ulsan National Institute of Science and Technology (UNIST), Ulsan 689-798, Korea) , Park, Joonmo (School of Mechanical and Advanced Materials Engineering, KIST-UNIST-Ulsan Center for Convergent Materials, Ulsan National Institute of Science and Technology (UNIST), Ulsan 689-798, Korea) , Kim, Sung Youb (School of Mechanical and Advanced Materials Engineering, KIST-UNIST-Ulsan Center for Convergent Materials, Ulsan National Institute of Science and Technology (UNIST), Ulsan 689-798, Korea) , Kim, Myung Hwa (김명화, Department of Chemistry and Nano Science, Ewha Womans University, Seoul 120-745, Korea) , Baik, Jeong Min (School of Mechanical and Advanced Materials Engineering, KIST-UNIST-Ulsan Center for Convergent Materials, Ulsan National Institute of Science and Technology (UNIST), Ulsan 689-798, Korea)
  • JOURNAL OF PHYSICAL CHEMISTRY C[1932-7447], 2013, v.117 no.42, 21864-21869

초록/요약

We report an unprecedented insulator-to-metal transition of the Pd-nanoparticle-decorated, single vanadium dioxide nanowires caused by the heterogeneous H-2-Pd catalytic reactions. Upon hydrogen gas exposure, the Pd-VO2 hetero-nanostructure shows a remarkably large current increase (similar to 1000-fold) at a temperature 10 degrees C lower than the insulator-to-metal transition temperature in the bulk. This current increase occurs slowly over the duration of several seconds to several tens of seconds, depending on the Pd coverage, temperature, and hydrogen concentration. After hydrogen flow is shut off, the conductance is not immediately returned to the original value and it takes several hours, indicating that the atomic hydrogens, produced by the dissociative chemisorption on Pd, are incorporated into VO2. From the electronic transport measurements and finite element analyses, we suggest that the slow transition is mainly due to the formation of alternating domains of metal and insulator regions of the VO2 crystal lattice, produced by the generated heat via the exothermic catalytic process. The current response toward hydrogen gas is also found to be reversible after the heating process. This novel finding thus has significant implications for the effective engineering of the physicochemical properties of vanadium dioxide by a heterogeneous catalytic process.

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