Pervasiveness of Surface Metal Oxide Phases In Mixed Oxide Catalysts
Israel E. Wachs
Lehigh University, Bethlehem, PA
Abstract – Mixed oxide catalytic materials possess two or more metal oxide components as found in bulk mixed metal oxides (stoichiometric oxides as well as solid solutions), polyoxo metalates (POMs), molecular sieves, zeolites, clays, hydrotalcites and supported metal oxides. Although it is now well established that two-dimensional surface metal oxide phases are present for supported metal oxides on traditional supports (e.g., Al2O3, TiO2, ZrO2, SiO2, etc.), it is not currently appreciated that such surface metal oxide species or phases are also present for other types of mixed oxides. For example, recent surface analyses have demonstrated that stoichiometric bulk mixed metal oxides also possess surface metal oxide phases that control their catalytic activity. For example, the catalytic active sites for methanol oxidation to formaldehyde over the bulk Fe2(MoO4)3 mixed oxide catalyst are surface MoOx species and not the bulk Fe2(MoO4)3 phase as previously thought in the catalysis literature. The nanometer sized clusters in POMs also possess surface species when a second metal oxide component is introduced (e.g., H3+xPW12-xMxO40). Deposition of metal oxides into molecular sieves, zeolites, clays and hydrotalcites also results in the metal oxide additive usually being present as surface metal oxide species that are the catalytic active sites for many redox and acid reactions. The formation of these surface metal oxide phases is driven by their low surface free energy and low Tammann temperature for many metal oxides of interest in catalysis (e.g., VOx, MoOx, CrOx, ReOx, WOx, etc.).
Supported Metal Catalysts — Issues and Opportunities
Stuart Soled, ExxonMobil
Sulfur-Resistant Pd– Alloy Membranes for H2 Purification
Jim Miller, Carnegie Mellon University
Nature of Catalytic Active Surface Sites on Semiconductor Photocatalysts for Splitting of Water
Somphonh Peter Phivilay, Lehigh University (Student Speaker)
John Kitchin, Carnegie Mellon
Meeting Program – April 2013
Department of Chemical Engineering,
Carnegie Mellon University
Abstract – Electrochemical water splitting may be in integral part of future energy storage strategies by enabling energy storage in chemical bonds. One of the primary sources of inefficiency in the water splitting reaction is the oxygen evolution reaction, which has high reaction barriers that require additional applied electric potential to drive the reactions at practical rates. The most active electrode materials in acid electrolytes include ruthenium and iridium oxides, which are expensive but necessary for stability. In alkaline environments, many base metal oxides become stable, although they are still less active than Ru and Ir oxides. It has been known that small amounts of Fe can promote the electrochemical activity of nickel oxides, making it almost as active as cobalt oxide. We have investigated the mechanisms behind the promotion using in situ Raman and synchrotron spectroscopies as well as ex situ characterization techniques. Interestingly, we found the electrode changes under oxygen evolution conditions, turning from an oxide to an oxyhydroxide phase. Furthermore, the composition of the electrolyte has a significant effect on the oxygen evolution activity. We will discuss these results and their implications in finding better oxygen evolution electrocatalysts.
Each year the Catalysis Club of Philadelphia recognizes an outstanding member of the catalysis community, who has made significant contributions to the advancement of Catalysis. Such advancement can be scientific, technological, or in organization leadership. The Award consists of a plaque and a $1000 cash prize.
We appreciate your help in submitting nominations. The entire nomination package, including a resume and recommendation letters, should not be more than 10 pages and should include a ½ page tentative award announcement. The deadline for the receipt of nominations is April 19, 2013. Prior nomination packages sent in 2011 or later will automatically be considered for the 2013 Award.
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Johnson Matthey ECT
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Catalysis – An Indispensable Tool
Sourav Sengupta, DuPont — 2015 CCP Award Winner
Prof. Matthew Neurock, University of Minnesota – Twin Cities
Jingguang Chen, Columbia University