(582au) Mechanistic Insights into the Effect of Electrolyte Composition on the Electroreduction of Carbon Dioxide (CO2) to C1-C2 Chemicals Using a Flow Electrolyzer

The electroreduction of carbon dioxide (CO₂) to value added C₁-C₂ chemical feedstocks (such as formic acid, carbon monoxide (CO), ethylene, ethanol) has been proposed as a potential strategy for utilizing excess anthropogenic CO₂ emissions.[1, 2] Starting with the seminal work of Hori et al.,[3] a variety of catalysts and electrolytes have been investigated for this reaction.[4] Specifically, for the electroreduction of CO₂ to CO on silver nanoparticle based electrodes, the electrolyte composition (especially pH) has been shown to play an important role with high concentrations of alkaline electrolyte improving the activity and lowering the overpotential required for this reaction.[5, 6]. However, the exact mechanism behind such a behavior is poorly understood.

In this poster presentation, we will attempt to provide mechanistic insights into the effect of electrolyte concentration and pH on the electroreduction of CO₂ to CO, by analyzing the onset potentials and the Tafel slope data on two different cathode catalysts i.e., silver nanoparticles, and carbon nanotube supported gold nanoparticles. All experiments were performed in a gas diffusion electrode based flow electrolyzer,[7] to avoid mass transfer limitations associated with the low solubility of CO₂ in aqueous solutions (~35 mM under standard conditions). Our results indicate that the rate determining step for the electroreduction of CO₂ to CO is a pH independent single electron transfer step and increasing the electrolyte pH can be a simple strategy for reducing the overpotential required for the reaction. In addition, this presentation will also focus on our recent results with regards to the mechanistic pathway involved in the electroreduction of CO₂ to C₂ products (such as ethylene and ethanol) on copper nanoparticle based catalysts.

References:

[1] A.M. Appel, J.E. Bercaw, A.B. Bocarsly, H. Dobbek, D.L. DuBois, M. Dupuis, J.G. Ferry, E. Fujita, R. Hille, P.J.A. Kenis, C.A. Kerfeld, R.H. Morris, C.H.F. Peden, A.R. Portis, S.W. Ragsdale, T.B. Rauchfuss, J.N.H. Reek, L.C. Seefeldt, R.K. Thauer, G.L. Waldrop, Chem. Rev. 2013, 113, 6621-6658.

[2] D.T. Whipple, P.J.A. Kenis, J. Phys. Chem. Lett. 2010, 1, 3451-3458.

[3] Y. Hori, H. Wakebe, T. Tsukamoto, O. Koga, Electrochim. Acta 1994, 39, 1833-1839.

[4] H.R.M. Jhong, S. Ma, P.J.A. Kenis, Curr. Opin. Chem. Eng. 2013, 2, 191-199.

[5] B. Kim, S. Ma, H.R.M. Jhong, P.J.A. Kenis, Electrochim. Acta 2015, 166, 271-276.

[6] S. Verma, X. Lu, S. Ma, R.I. Masel, P.J.A. Kenis, Phys. Chem. Chem. Phys. 2016, 18, 7075-7084.

[7] D.T. Whipple, E.C. Finke, P.J.A. Kenis, Electrochem. Solid-State Lett. 2010, 13, B109-B111.