(617hf) Conversion of Carbon Dioxide to Syngas Using Transition Metal Dichalcogenide Catalysts

Mohammad Asadi, Pedram Abbasi, Amin Salehi-Khojin

Department of Mechanical and Industrial Engineering, University of Illinois at Chicago, Chicago, IL, 60607, USA.

Abstract:

Carbon dioxide (CO₂) concentration in the atmosphere has drastically increased in the past 50 years and is expected to reach the maximum level in the next few decades (2060) due to fossil fuels consumption using existing infrastructure¹. It is recognized that the CO₂ level can be controlled by sequestrating^2,3or converting it into useful energy-rich products^4,5. The conversion approach is more desirable since it not only offers an efficient path for CO₂ remediation but also provides a sustainable energy source. Among various remediation techniques, electrochemical reduction of carbon dioxide (CO₂) offer convenient ways to recycle CO₂ into fuels^4,5. However, it has been advanced far more slowly in the last two decades, mainly due to insufficient performance of existing catalysts⁶. Fundamentally, the electronic structure of commonly used catalysts is not well-suited for the electrochemical CO₂ reduction reaction⁷. The high density of active d-orbital electrons near the Fermi level together with a low work function are essential to catalyze this process⁸. However, the majority of existing catalysts are far below the ideal limits of these properties.

In a search of cost and energy efficient catalysts, here, we report results for transition metal dichalcogenide (TMDC) nanoflakes (NFs) that exhibit extraordinary catalytic activity for CO₂ reduction in the ionic liquid (IL) 1-ethyl-3-methylimidazolium tetrafluoroborate (EMIM-BF₄). Our results indicate that the tungsten diselenide (WSe₂) isthe most active catalyst for CO₂ reduction and exhibits more than two orders of magnitude better conversion performance compared to commonly used catalysts in the literature. Atomic level study of WSe₂ NFs before and after electrochemical experiments using scanning transmission electron microscopy (STEM) indicate that; (i) mainly tungsten (W) atoms on the edge sites are responsible for this remarkable activity and (ii) the edge sites remain stable during the reaction. Our electrochemical impedance spectroscopy (EIS) and work function measurements also reveal that the high electrocatalytic activities of TMDC NFs mainly rely upon the fast electron transfer to the intermediate complex resulting in the low overpotential and high current density for conversion of CO₂ to the syngas.

References:

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