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Fundamental Studies of Water Splitting on Model TiO2, RuO2 and Mixed TiO2-RuO2 Catalysts


EMSL Project ID
47406

Abstract

The objective of this project is to provide fundamental insights into the roles of co-catalysts in heterogeneous photocatalytic water splitting over model TiO2 and related semiconducting oxide materials. There is an obvious need for new fundamental insights into photocatalytic water splitting particularly how to design catalyst systems that extend the catalytic and photocatalytic functionalities of simple materials (like TiO2) through the use of co-catalysts, dopants (to increase photoabsorptivity), promoters (to increase chemical activity) and tandem systems.
RuO2 has been widely used as a co-catalysis supported on TiO2 to promote both water photoreduction and photooxidation. However, the fundamental science of how RuO2 functions as a co-catalyst in these water splitting reactions is not well-understood. It is generally believed that RuO2 does not promote optical absorption or extend the absorptivity of the photocatalyst into previously inaccessible spectral regions, but instead that RuO2 as co-catalyst promotes thermal reactions that do not readily occur on the photocatalyst itself. Nevertheless, the role of RuO2 as a co-catalyst in charge separation and trapping has not been well explored.
We propose examining the thermal and photochemical properties of RuO2, both as a stand-alone catalyst and as co-catalyst with TiO2, for water splitting (to H2 and/or O2), as well as the importance or RuO2 as a co-catalyst in H2 (and O2) utilization reactions. Like the thermodynamically most stable form of TiO2, RuO2 readily adopts the rutile structure. Pure RuO2 films and clusters with the rutile (110) orientation can be grown directly on TiO2(110) or on Ru(0001) by oxidation. Similarly, rutile TiO2(110) films and clusters can be grown on RuO2(110) or mixed films of these oxides (i.e., TixRu1-xO2(110)) can also be prepared. We will employ a variety of state-of-the-art surface science approaches (e.g., STM, TPD, vibrational spectroscopies, electron spectroscopies, etc.) to examine the mechanisms, energetics and surface site dependences for water splitting. The role of RuO2 as a photocatalyst and co-photocatalyst will also be explored using the probe reactions (e.g., O2 photodesorption and photodissociation, trimethyl acetate photodecomposition and methyl radical evolving processes). This research effort will provide deeper insight into not only chemistry and photochemistry of water splitting but also into relationships between catalysts and co-catalysts.

Project Details

Project type
Large-Scale EMSL Research
Start Date
2012-10-01
End Date
2014-09-30
Status
Closed

Team

Principal Investigator

Michael Henderson
Institution
Pacific Northwest National Laboratory

Co-Investigator(s)

Nathaniel Deskins
Institution
Worcester Polytechnic Institute

Team Members

Kumarasegaran Subramaniyam
Institution
Pacific Northwest National Laboratory

Gustavo Martinez
Institution
University of Texas at El Paso

Igor Lyubinetsky
Institution
Pacific Northwest National Laboratory

Gregory Herman
Institution
Oregon State University

Gregory Kimmel
Institution
Pacific Northwest National Laboratory

Mark Engelhard
Institution
Environmental Molecular Sciences Laboratory

Zdenek Dohnalek
Institution
Pacific Northwest National Laboratory

David Dixon
Institution
University of Alabama

Related Publications

Chen L, Z Li, RS Smith, BD Kay, and Z Dohnalek. 2014. "Molecular Hydrogen Formation from Proximal Glycol Pairs on TiO2(110)." Journal of the American Chemical Society 136(15):5559-5562. doi:10.1021/ja500992b
Flynn BT, KHL Zhang, V Shutthanandan, T Varga, RJ Colby, RP Oleksak, S Manandhar, MH Engelhard, SA Chambers, MA Henderson, GS Herman, and S Thevuthasan. "Growth and Surface Modification of LaFeO3 Thin Films Induced By Reductive Annealing." Applied Surface Science. doi:10.1016/j.apsusc.2015.01.028
Henderson MA. 2013. "Photooxidation and Photodesorption in the Photochemistry of Isobutene on TiO2(110)." Journal of Physical Chemistry C 117(27):14113-14124. doi:10.1021/jp404625c
Henderson MA, M Shen, Z Wang, and I Lyubinetsky. 2013. "Characterization of the Active Surface Species Responsible for UV-Induced Desorption of O2 from the Rutile TiO2(110) Surface." PNNL-SA-93363, Pacific Northwest National Laboratory, Richland, WA. [Unpublished]
Petrik NG, and GA Kimmel. 2013. "Multiple Non-Thermal Reaction Steps for the Photooxidation CO to CO2 on Reduced TiO2(110)." The Journal of Physical Chemistry Letters 4(3):344-349. doi:10.1021/jz302012j
Shen M, and MA Henderson. 2012. "Role of Water in Methanol Photochemistry on Rutile TiO2(110)." Journal of Physical Chemistry C 116(35):18788–18795. doi:10.1021/jp3046774
X. Lin, Z. Li, Z.-T. Wang, I. Lyubinetsky, B.D. Kay, and Z. Dohnalek, Interaction of CO2 with Oxygen Adatoms on Rutile TiO2(110), Phys. Chem. Chem. Phys. 15 (2013), 6190-5 (featured on journal cover).
Yoon Y, Y Du, JC Garcia, Z Zhu, Z Wang, NG Petrik, GA Kimmel, Z Dohnalek, MA Henderson, RJ Rousseau, NA Deskins, and I Lyubinetsky. 2015. "Anticorrelation between Surface and Subsurface Point Defects and the Impact on the Redox Chemistry of TiO2(110)." Chemphyschem 16(2):313-321. doi:10.1002/cphc.201402599