Why this paper? As a Senior Research Scientist, I traveled to Japan to work on nancomposites, such as Pt/TiO2 and Au/TiO2. I and my Japanese, Korean, and Chinese collaborators accomplished alot in a 3 month period. When I returned, I brought some of the insight from that research back to Battelle-PNNL. At EMSL, we worked to refine what we had done and push our understanding of rutile and anatase forms of TiO2 into practical forms. The research represented by this paper from Korea, represents yet another great advance and affirmation of our previous work. Which makes us happy, of course. We have always looked for solutions to end fossil-fuel energy systems. This is one of those successful attempts.
Chyan Kyung Song
School of Chemical and Biological Engineering
The Graduate School, Seoul National University
“In order to solve the environmental pollution occurring around the world, it is essential to develop a catalytic system based on readily available energy sources. Photocatalystic systems have received a lot of attention, since those do not require additional waste of energy for the use of catalysts and can be used wherever light is present. In this study, noble metal supported titanium dioxide (TiO2) systems were synthesized based on the concept that noble metal nanoparticles like Au and Pt can utilize visible light in photocatalysis. TiO2 is a generally used semiconductor material due to chemical stablility, nontoxicity and economically availability, although having the inferior property of hardly absorbing light in the visible light region. However, TiO2 is a strong candidate as photocatalytic material by supporting metal nanoparticles which assists to utilize visible light. Methodologies were suggested for enhancing photocatalytic performance focusing on the metal-TiO2 systems.
“The phase and morphology of TiO2 were optimized to enhance a photocatalytic performance under visible light region. It was identified that rutile phase TiO2 of three dimensional structure is the most probable photocatalytic system among Au/TiO2. Local surface plamonic resonance (LSPR) life time of gold nanoparticles prolonged and efficient plasmonic interaction occurred due to the three dimensional morphology of TiO2, and photocatalytic performance was observed to be increased. Furthermore, hot electrons generated from LSPR more efficiently transfer to rutile TiO2 than anantase TiO2. Hot electrons can favorably transfer from Au to rutile TiO2 due to the overlapping DOS of Au and rutile TiO2 conduction band, and the electron transfer of opposite direction could be blocked by larger band bending of rutile TiO2…
“…It was once considered that the CB minimum in anatase TiO2 is ~0.2 eV higher than rutile TiO2. However, an opposite view has arisen to be fact in the recent studies, which supports the conclusion that the CB minimum in rutile TiO2 is ~0.2 eV higher than anatase TiO2 [66,67]. Hence, both ϕSB and VBB would be expected to be higher in the Au/rutile TiO2 system. Furthermore, due to the higher band shift in Au/rutile TiO2 observed in DFT calculations, VBB becomes higher which delays electron-hole recombination. Therefore, it can be concluded that more electrons are transferred from Au to rutile TiO2 and less electrons are transferred from rutile TiO2 to Au than in case of anatase TiO2…”
 G. Xiong, R. Shao, T. C. Droubay, A. G. Joly, K. M. Beck, S. A. Chambers, W. P. Hess, Adv. Funct. Mater. 2007, 17, 2133-2138.
“…The findings revealed that due to the stronger bond between Au and rutile TiO2 and
the overlapping of Au DOS in the rutile TiO2 CB, Au/rutile TiO2 is more advantageous in both hot electron transfer and the quantity of electrons. Furthermore, the reverse transfer path is obstructed in Au/rutile TiO2, due to
the larger band bending induced by thermodynamic energy level of rutile TiO2
CB, which delays the recombination between electrons and holes in Au. An effective charge-separation pathway was proposed in the M-S junctioned photocatalytic system via a synergetic electron and hole-transfer mechanism…”
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