A cyclic electrochemical strategy to produce acetylene from CO, CH, or alternative carbon sources

• Published in: Sustainable energy & fuels Vol. 4; no. 6; pp. 2752 - 2759
• Main Authors: McEnaney, Joshua M, Rohr, Brian A, Nielander, Adam C, Singh, Aayush R, King, Laurie A, Nørskov, Jens K, Jaramillo, Thomas F
• Format: Journal Article
• Language: English
• Published: 02.06.2020
• ISSN: 2398-4902
• DOI: 10.1039/c9se00799g

Electrochemical transformation of potent greenhouse gases such as CO 2 and CH 4 to produce useful carbon-based products is a highly desirable sustainability goal. However, selectivity challenges remain in aqueous electrochemical processes as selective CO 2 reduction to desired products is difficult and electrochemical CH 4 oxidation often proceeds at very low rates. The formation of C-C coupled products in these fields is particularly desirable as this provides a path for the production of high-value fuels and chemicals. We have developed a cyclic electrochemical strategy which can produce acetylene, a C-C coupled product, from such carbon sources and water, with favorable current density and selectivity. This strategy is exemplified with a lithium-mediated cycle: an active Li 0 surface is electrochemically generated from LiOH, the newly formed Li 0 reacts with a carbon source to form Li 2 C 2 , and Li 2 C 2 is hydrolyzed to form acetylene and regenerate LiOH. We demonstrate this process primarily using CO 2 gas, achieving a current efficiency of 15% to acetylene (which represents 82% of the maximum based on stoichiometric production of oxygenated byproducts, e.g. LiCO 3 and/or Li 2 O), as verified by gas chromatography and Fourier transform infrared radiation studies. We also explore CH 4 , CO, and C as alternative precursors in the acetylene synthesis. Notably, the use of graphitic carbon at higher temperatures resulted in over 55% current efficiency to acetylene, with opportunity for further optimization. Importantly, this cycling method avoids the formation of common side products observed during aqueous electrochemical CO 2 and CH 4 redox reactions, such as H 2 , CO, HCO 2 − , or CO 2 . Theoretical considerations elucidate the feasibility and general applicability of this cycle and the process steps have been characterized with specific electrochemical and materials chemistry techniques. The continued development of this strategy may lead to a viable route for the sustainable production of C-C coupled carbon fuels and chemicals. The electrochemical transformation of potent greenhouse gases and low-value carbon sources to produce useful carbon-based products is a highly desirable sustainability goal.