Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Catalysis: Ready for a close-up

30.08.2012
The latest advance in imaging technology helps optimize catalysts for use in onboard fuel processing. A*STAR researchers have identified the subtle, atomic-scale structural transformations that can activate and de-activate gold nanoparticle catalysts, a finding that may lead to longer-lasting hydrogen fuel cells.

The presence of carbon monoxide (CO) impurities in hydrogen gas (H2) can have a detrimental impact on the performance of fuel cells. Recent studies have shown that gold nanoparticles — particles less than five nanometers wide — can catalytically remove CO impurities from H2 under mild temperature and pressure conditions.

This breakthrough understanding has helped facilitate the development of fuel-cell vehicles that use ‘onboard’ fuel processing technology. Unfortunately, gold nanoparticles tend to lose their catalytic activity after a few hours of use — and scientists need to overcome this problem if gold nanoparticles are to be used.

Ziyi Zhong at the A*STAR Institute of Chemical and Engineering Sciences, Ming Lin at the A*STAR Institute of Materials Research and Engineering and co-workers have identified the subtle, atomic-scale structural transformations that can activate and de-activate gold nanoparticle catalysts, a finding that may lead to longer-lasting hydrogen fuel cells.

The researchers set out to design an improved catalyst for so-called preferential oxidation (PROX) reactions. This approach transforms CO impurities into carbon dioxide (CO2) on a ceramic support containing metal catalysts. Previously, the team found that silica-based supports, called SBA-15, could boost CO removal by selectively absorbing the CO2 by-product. The researchers took advantage of another SBA-15 characteristic — a mesoporous framework decorated by terminal amine groups — to engineer a novel PROX catalyst.

First, the team used amine modification to disperse a mixture of gold and copper(II) oxide (CuO) precursors evenly over the SBA-15 support. They then used heating treatment to generate gold and CuO nanoparticles on the SBA-15 support. The numerous pores in SBA-15 and the CuO particles work together to hinder agglomeration of gold nanoparticles — a major cause of catalyst de-activation.

The team then achieved a near-unprecedented chemical feat: localized structural characterization of their catalyst at atomic scale, using high-resolution transmission electron microscopy (HR-TEM) and three-dimensional electron tomography (see movie below). These imaging techniques revealed that the active catalyst sites — gold or gold–copper alloy nanoparticles in the immediate vicinity of amorphous and crystalline CuO — remained stable for up to 13 hours. However, the reducing atmosphere eventually transforms CuO into copper(I) oxide and free copper; the latter of which then alloys with the gold nanoparticles and deactivates them. Fortunately, heating to >300°C reversed the alloying process and restored the catalyst’s activity.

“People working in catalysis are always curious about the ‘local structures’ of their materials,” says Zhong. “Because the Au-CuO/SBA-15 catalyst is active at room temperature, advanced characterization in our state-of-the-art facilities is possible — though it takes great patience and requires multidisciplinary collaboration.”
The A*STAR-affiliated researchers contributing to this research are from the Institute of Chemical and Engineering Sciences and the Institute of Materials Research and Engineering

References:

Li, X., Fang, S. S. S., Teo, J., Foo, Y. L., Borgna, A. et al. Activation and deactivation of Au–Cu/SBA-15 catalyst for preferential oxidation of CO in H2-rich gas. ACS Catalysis 2, 360–369 (2012).

A*STAR Research | Research asia research news
Further information:
http://www.research.a-star.edu.sg
http://www.researchsea.com

More articles from Life Sciences:

nachricht Polymers Based on Boron?
18.01.2018 | Julius-Maximilians-Universität Würzburg

nachricht Bioengineered soft microfibers improve T-cell production
18.01.2018 | Columbia University School of Engineering and Applied Science

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Scientists decipher key principle behind reaction of metalloenzymes

So-called pre-distorted states accelerate photochemical reactions too

What enables electrons to be transferred swiftly, for example during photosynthesis? An interdisciplinary team of researchers has worked out the details of how...

Im Focus: The first precise measurement of a single molecule's effective charge

For the first time, scientists have precisely measured the effective electrical charge of a single molecule in solution. This fundamental insight of an SNSF Professor could also pave the way for future medical diagnostics.

Electrical charge is one of the key properties that allows molecules to interact. Life itself depends on this phenomenon: many biological processes involve...

Im Focus: Paradigm shift in Paris: Encouraging an holistic view of laser machining

At the JEC World Composite Show in Paris in March 2018, the Fraunhofer Institute for Laser Technology ILT will be focusing on the latest trends and innovations in laser machining of composites. Among other things, researchers at the booth shared with the Aachen Center for Integrative Lightweight Production (AZL) will demonstrate how lasers can be used for joining, structuring, cutting and drilling composite materials.

No other industry has attracted as much public attention to composite materials as the automotive industry, which along with the aerospace industry is a driver...

Im Focus: Room-temperature multiferroic thin films and their properties

Scientists at Tokyo Institute of Technology (Tokyo Tech) and Tohoku University have developed high-quality GFO epitaxial films and systematically investigated their ferroelectric and ferromagnetic properties. They also demonstrated the room-temperature magnetocapacitance effects of these GFO thin films.

Multiferroic materials show magnetically driven ferroelectricity. They are attracting increasing attention because of their fascinating properties such as...

Im Focus: A thermometer for the oceans

Measurement of noble gases in Antarctic ice cores

The oceans are the largest global heat reservoir. As a result of man-made global warming, the temperature in the global climate system increases; around 90% of...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

10th International Symposium: “Advanced Battery Power – Kraftwerk Batterie” Münster, 10-11 April 2018

08.01.2018 | Event News

See, understand and experience the work of the future

11.12.2017 | Event News

Innovative strategies to tackle parasitic worms

08.12.2017 | Event News

 
Latest News

Polymers Based on Boron?

18.01.2018 | Life Sciences

Bioengineered soft microfibers improve T-cell production

18.01.2018 | Life Sciences

World’s oldest known oxygen oasis discovered

18.01.2018 | Earth Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>