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Title Discovers Cause of Local Strain of Pt. Nano Catalyst that Takes Place during Methane Gas Catalytic Reaction
Writer sogpr Date 2018-10-04 Views 602

Research Team Led by Prof. Kim Hyun-jung of Physics Department

Discovers Cause of Local Strain of Pt. Nano Catalyst

that Takes Place during Methane Gas Catalytic Reaction

- Expected to Contribute to Catalyst Engineering and Design, the Core Industry for the Future -

 

 

▲Prof. Kim Hyun-jung (left), Kim Dong-jin Ph.D. student (right)

 

A research team led by Prof. Kim Hyun-jung of the Physics Department has discovered the cause of local strain generated in the catalytic reaction of platinum nano-crystals by implementing the 3D imaging of a single crystal. The research was posted in the online edition of world-renowned journal ‘Nature Communications’ (Impact Factor 12.353, as of 2017) on August 24.

 

Thesis Information

- Title: Active site localization of methane oxidation on Pt nano-crystals

- Authors: Prof. Kim Hyun-jung (Corresponding author); Kim Dong-jin (Primary author, PhD course at Sogang University)

 

A platinum nano-crystal is a matter broadly used in industrial areas, such as for vehicle catalyst converters, fuel cells, electronic catalytic reactions, etc. To this point, there have been research projects on the measurement of average metamorphosis in whole poly-crystals; however, this new research represents a first-time discovery of the cause of local strain in a single crystal through a catalytic reaction based on 3D imaging – in other words: theoretical simulation. Prof. Kim Hyun-jung’s team used the coherent x-ray diffraction method to achieve 3D imaging for grid strains at the atomic-level.

 

The significance of this research is found in strain locations and the cause of the catalyst crystal participating in the catalytic reaction, thus deepening the understanding of the catalyst oxidation mechanism. Through this, the decrease of catalyst efficiency due to crystal strain can be prevented, and it is expected that a wider variety of catalyst designs based on nano-crystals will be realized. In particular, in this research, the methane catalytic reaction was applied as an example of a catalytic reaction. This methane catalytic reaction can be utilized for studies on converting methane gas, which causes various environmental issues, including global warming.

 

Prof. Kim Hyun-jung stated, “The results from the research are found by realizing the 3D image of strains in the metal catalyst generated from the catalyst reaction at the atomic-level, including absorption, dissociation, reaction generation, and desorption, in theoretical and experimental ways,” and added, “It is projected that this will contribute to the improved design of future catalysts.”

 

On the other hand, this study was implemented using the Advance Photon Source, a cutting-edge radiance accelerator from the U.S. Argonne National Laboratory, and PETRA III, a German device, and it was sponsored by the Ministry of Science and ICT through the project for researcher support and the project for advanced research center support by the National Research Foundation of Korea.

 

Relevant Figures and Their Descriptions

 

▲ Figure 1. Changes in the x-ray diffraction pattern coherent to platinum nano-crystals during the catalytic reaction

 

a-f. Coherent x-ray diffraction pattern of platinum nano-crystals, measured in different air environments

a. diffraction pattern under 1% hydrogen gas air environment

b. diffraction pattern under 20% oxygen gas air environment (after 2.5 minutes)

c. diffraction pattern under 20% oxygen gas air environment (after 36 minutes)

d. diffraction pattern under 1% methane gas air environment (after 2.5 minutes)

e. diffraction pattern under 1% methane gas air environment (after 16 minutes)

f. diffraction pattern under 1% methane gas air environment (after 36 minutes)

 

 

▲ Figure 2. Comparison between experiment results from coherent x-ray diffraction imaging (left) and

calculated values according to theory (right)

 

a-d. The distribution of crystal strain from coherent x-ray diffraction imaging is shown in the picture; left is the 3D imaging and right is the vertical section cut in the direction of the crystal [111]. The conditions for a-d are identical with the conditions of Figures 1a, b, d, and f, respectively. The strain takes place around the corners of a crystal in the oxygen environment and in the initial methane environment; the strain looks remarkable. When the catalytic reaction is complete, the strain disappears and the original form is restored. The red area signifies the grid in the specimen with strain in the direction of [111], while the blue area shows strain in the opposite direction.

e. Using finite element analysis, the value of force gained from the reacting molecules dynamics simulation was applied to the edge of the crystal.

f-g. According to the calculations, the results are identical with the grid distribution measured by the coherent x-ray diffraction imaging method. Under the oxygen environment, the compressing force from the chemical absorption of oxygen causes strong strain around the corner of the crystal; under the methane environment where the catalytic reaction takes place, the strain becomes stronger. Then, once the reaction is complete, desorption takes place and the strain is restored.