AsianScientist (Mar. 22, 2016) – Korean researchers have created a catalytic nanodiode that allows them to observe in real time the flow of ‘hot’ electrons generated by chemical reactions. Their findings, published in Nano Letters, could help design catalytic and energy materials with improved performance and lower costs.
From converting vehicle exhaust fumes into less harmful gases to refining petroleum, most commercial chemical applications require nanocatalysts. Activity and selectivity largely depends on the catalyst’s physical properties as well as the electronic characteristics—the dynamics of ‘hot’ (high energy) electrons on the surface and interface of catalysts.
Hot electrons, which are an indicator of catalytic activity, are created when excess energy from the surface of a chemical reaction is permitted to dissipate. However, because they dissipate in a matter of femtoseconds, directly detecting hot electrons remains challenging.
In this study, researchers from the Institute for Basic Science, working under the Center for Nanomaterials and Chemical Reactions’ group leader, Professor Park Jeong Young, extracted ‘hot carriers’ from a metal catalyst using a graphene-semiconductor junction.
Instead of the gold used in previous experiments, the team used a single layer of graphene grown on a copper film and transported to a layer of titanium film. Graphene was used for its unique electronic and chemical properties.
When integrated with platinum nanoparticles, the graphene-based catalyst showed tremendous improvement in conductivity performance. This then allowed the researchers to measure the catalytic activity and amount of hot electrons. They found that the catalytic activity and the generation of hot electrons were well-matched.
“Graphene-based nanostructures, such as ours are promising detectors for the study of hot electron dynamics on metal nanoparticles during the course of catalytic reactions,” the team wrote in the paper.
The team’s work highlights the lowered contact resistance at the nanoparticle/graphene interface as the main characteristic leading to efficient hot electron detection on the nanocatalysts in the graphene-based catalytic nanodiode.
By utilizing a single layer of graphene for electrical connection of the platinum nanoparticles it allowed for easier observation of hot electrons because of both the atomically thin nature of graphene and the reduced height of the potential barrier existing at the nanoparticle/graphene interface.
First author and PhD student Ms. Lee Hyosun said, “Even though there is still the potential for improving the quality of the graphene layer itself and its contact with the TiO2, the approach presented here offers a new way to study the roles of graphene during heterogeneous catalysis.”
The article can be found at: Lee at al. (2016) Graphene–Semiconductor Catalytic Nanodiodes for Quantitative Detection of Hot Electrons Induced by a Chemical Reaction.
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Source: Institute for Basic Science.
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