A catalytic support material takes a leading role

July 25, 2018 by Jared Sagoff And Joe Harmon, Argonne National Laboratory
Argonne chemists have uncovered an important and unexpected reaction mechanism –called “redox behavior”–on the surface of catalyst support materials. These materials are promising catalytic materials in their own right. Credit: Argonne National Laboratory

Scientists at the U.S. Department of Energy's (DOE) Argonne National Laboratory, in collaboration with DOE's Ames Laboratory, have reported an important and unexpected reaction mechanism—called "redox behavior"—on the surface of catalyst support materials that have application in the chemical industry.

Most industrial catalysts are anchored to metal oxide supports such as silica, alumina or zirconia. Recently, sulfated metal oxides have emerged as a promising support material for carbon-containing metallic ("organometallic") catalytic complexes. They are also promising catalytic materials in their own right, with application to chemical processes in the petrochemical industry.

Using a combination of theoretical calculations and measurements with advanced analytical techniques, the research team investigated the interactions between an organometallic iridium catalyst and support materials composed of sulfated alumina and sulfated zirconia. These interactions took place during a catalytic reaction promoted by the organo-iridium species with the support .

Thanks to previous research, scientists had been aware of a catalysis pathway that involves the donation of protons from the sulfated metal oxides. The research team discovered a second pathway, a redox reaction involving the acceptance of electrons from the organometallic complex on the sulfated metal oxide surface. They also discovered that some sites on the sulfated metal surface that had been proton-donating could be transformed into electron-accepting sites, thereby changing the organometallic catalyst's chemical behavior.

Argonne chemist Max Delferro, an author of the study, commented that "in this redox mechanism, our material takes its usual chemical routine and turns it on its head—instead of giving up a proton, it gains an electron."

The appearance of the hydrogen isotope deuterium in the organometallic complex signaled the occurrence of a redox reaction that had not previously been reported. In addition, the researchers found that both surface hydration and sulfate loading in the support material play a key role in the redox process.

According to Delferro, the research provides insights to the catalysis community concerning the potential for similar mechanisms to form an important part of catalytic relationships, including those in which supporting surfaces act as their own catalyst. "This observation provides a proof of principle that an important set of reactions is happening and should not be ignored," said Argonne postdoctoral researcher David Kaphan, another author of the study.

The study, titled "Evidence for redox mechanisms in organometallic chemisorption and reactivity on sulfated oxides," appeared in the April 9 online issue of the Journal of the American Chemical Society.

Explore further: Scientists make vanadium into a useful catalyst for hydrogenation

More information: Rachel C. Klet et al. Evidence for Redox Mechanisms in Organometallic Chemisorption and Reactivity on Sulfated Metal Oxides, Journal of the American Chemical Society (2018). DOI: 10.1021/jacs.8b00995

Related Stories

Molecular wave of nanosized metal oxide catalyst

May 24, 2016

Metal oxides represent primary source of catalytic materials for a variety of industrial and research applications, either as an active phase or as a supporting phase. A mechanistic study has revealed the formation of catalytically ...

Oxygen takes elitist attitude to sharing electrons

November 23, 2016

Fuel cells, metal-air batteries, and other devices use electron-exchanging reactions involving gaseous oxygen. To improve these technologies, scientists need to know how the oxygen behaves when it encounters the catalyst, ...

Astonishing effect enables better palladium catalysts

May 15, 2018

In chemistry, atoms can usually only affect their immediate neighborhood. At TU Vienna, a novel effect with astonishing long-range action has been discovered, which can make automotive catalytic converters more effective.

What a mesh

March 30, 2018

A team of scientists from across the U.S. has found a new way to create molecular interconnections that can give a certain class of materials exciting new properties, including improving their ability to catalyze chemical ...

Recommended for you

Zapping a new approach to solar cells

August 13, 2018

A simple and fast microwave experiment with the common chemical element phosphorus at Flinders University has opened the prospect of more affordable and effective super-thin solar cells.

Hybrid catalyst with high enantiomer selectivity

August 9, 2018

A group of Japanese researchers has developed a technology to create a hybrid catalyst from simple-structured, commercially available rhodium and organic catalysts, which reduces chemical waste and produces molecules with ...

0 comments

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.