In the world of catalysis, gold nanoparticles have been hailed as one of the most effective catalysts for chemical reactions, particularly oxidation reactions. However, their performance can be limited when mounted on irreducible oxides like silica. This is where a team of researchers from Tokyo Metropolitan University has found a solution – adding single nanosheets of mixed metal oxide (MMO) as a topcoat to enhance their catalytic activity.
Their findings, published in the journal ACS Applied Materials & Interfaces, demonstrate the potential for developing high-performance catalysts that could revolutionize various industries.
The Power of Nanoscale Topcoats
The research team led by Associate Professor Tamao Ishida has developed a method to deposit single nanosheets of mixed metal oxides using layered double hydroxides (LDHs). These LDHs consist of metal hydroxide nanosheets with some metal ions substituted by ions with a higher charge, giving them a net positive charge. The sheets are then bound together by negative ions and can be exfoliated and used separately.
In this study, the team coated gold nanoparticles supported on silica with positively-charged LDH nanosheets consisting of aluminum and other metals. This structure was then exposed to high temperatures (calcination) to form an ultra-thin layer of MMO on top of the gold nanoparticles.
Using transmission electron microscopy, the team observed that the nanoparticles were coated with a layer less than one nanometer in thickness. To test their performance, they used them to convert carbon monoxide to carbon dioxide and found that their new catalyst showed a conversion rate of 50% at only 50°C, a significant improvement over existing methods which require temperatures of over 300°C. It was also found to outperform popular impregnation methods for MMO coating.
Interestingly, the team found that thicker MMO layers led to worse performance. The key to achieving high performance lies in having a sub-nanometer coating. Further analysis of a cobalt aluminum MMO layer revealed an abundance of oxygen defects, highlighting the importance of this ultra-thin layer in enhancing catalytic activity.
The Future of High-Performance Catalysts
The potential applications for this new catalyst are vast. Converting harmful carbon monoxide into carbon dioxide is just one example; it could also be used in other oxidation reactions and potentially revolutionize industries such as fuel cells and chemical production.
Our method provides an efficient way to add catalytically active sites on metal oxide-supported gold nanoparticles. We hope our findings will pave the way for developing new high-performance catalysts with enhanced catalytic activity.
Associate Professor Ishida
This groundbreaking research has opened up new possibilities for enhancing catalytic performance by utilizing nanoscale topcoats. The team’s findings have been published in the journal ACS Applied Materials & Interfaces and can be accessed at https://phys.org/news/2024-03-nanoscale-topcoat-turbocharge-gold-nanoparticle.html.
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