New catalyst converts greenhouse gases into hydrogen gas

A new nanocatalyst has been developed that converts important greenhouse gases such as carbon dioxide (CO2) and methane (CH4) into hydrogen gas with a high added value (H2). This catalyst is expected to make a great contribution to the development of various technologies for converting waste to energy, as it has more than twice the conversion efficiency of methane to hydrogen compared to conventional electrode catalysts.

A research team led by Professor Gun-Tae Kim in the Faculty of Energy and Chemical Engineering has developed a method to improve the performance and stability of catalysts used in the reaction (i.e. dry reforming of methane, DRM) to produce H2 and carbon monoxide (CO) from known greenhouse gases such as CO2 and CH4 are used.

The conventional catalysts used for dry reforming methane (DRM) are nickel (Ni) based metal complexes. However, over time, the performance of the catalysts deteriorates, as does the life of the catalyst. This is because carbon accumulates on the surface of the catalysts when the catalysts clump together or their reaction is repeated at a higher temperature.

Number. 1 Schematic comparison, SEM images, the correlation between the number of ALD cycles and the particle size / population as well as X-ray photoelectron curves for the samples. (A) Conventional resolution for LSTN and (B) corresponding SEM image of LSTN. Scale bar, 500 nm. (C) Topotactic resolution via ALD for LSTN-20C-Fe and the corresponding SEM image of (D) LSTN-20C-Fe after reduction. Scale bar, 500 nm.

“The uniform and quantitatively controlled iron layer (Fe) through atomic layer deposition (ALD) facilitates topotactic dissolution and increases finely dispersed nanoparticles,” says Sangwook Joo (combined MS / PhD at the School of Energy and Chemical Engineering, UNIST). the first author of the study.

The research team also confirmed that dissolution is promoted even with a very small amount of ALD-deposited Fe oxide (Fe2O3). “Especially with 20 cycles of Fe-oxide deposition via ALD, the particle population reaches over 400 particles (Ni-Fe alloys),” says Arim Seong (combined MS / PhD at the School of Energy and Chemical Engineering, UNIST), the first Co-author of the study. “Since these particles consist of Ni and Fe, they also showed high catalytic activity.”

Figure 2. Catalytic properties of the DRM. (A) Methane converted during the DRM reaction for LSTN, LSTN-10C-Fe and LSTN-20C-Fe. (B) The activation energy of methane reactivity, calculated for LSTN, LSTN-10C-Fe and LSTN-20C-Fe. (C) Time dependence of the CH4 reactivity and the H2 / CO ratio for LSTN-20C-Fe in DRM at 700 ° C.

The new catalyst exhibited high catalytic activity for the DRM process with no observable degradation in performance for more than 410 hours of continuous operation. Their results also showed high methane conversion (over 70%) at 700ºC. “This is more than twice the efficiency of power conversion compared to conventional electrode catalysts,” says Professor Kim. “Overall, the abundant alloy nanocatalysts via ALD are an important step forward in the development of dissolution and its application in the energy use field.”

The results of this research were published in Science Advances, a sister journal of science, on August 26, 2020. In this study, Professor Jeong Woo Han from POSTECH, Professor John M. Vohs and Professor Raymond J. Gorte from the University of Pennsylvania, USA took part jointly.

Journal reference

Sangwook Joo, Arim Seong, Ohhun Kwon et al.

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