Rising atmospheric carbon dioxide (CO₂) levels and the associated rise in global temperatures have been brought to light as major global concerns. In fact, annual atmospheric CO₂ emissions have risen from about 2 Gt to 10 Gt in the last 5 decades.¹ Electricity production (via fossil fuel, etc.) is a large contributor, accounting for 37% of total CO₂ emissions, and therefore scientists have turned to renewable energy as a mitigation strategy.^2,3 Another widely-studied approach has been to reduce CO₂ to value-added chemicals and fuels (carbon monoxide, ethanol, formic acid, etc.). Previous works have aimed at increasing the feasibility of the CO₂ electroreduction (CO₂RR). Being able to improve and control the selectivity of CO₂RR would greatly contribute to its industrial application.

Developing thermodynamically efficient and kinetically active catalysts is a key part of CO₂RR. Depending on the catalyst or operating conditions, a variety of products can be formed.⁴ Hydrocarbons and oxygenates, such as ethanol and methanol, are attractive products because of their high-energy density and variability in application.⁵ For example, methanol is a feedstock for the industrially mature methanol to gasoline (MTG) process, which has a 95% thermal energy conversion efficiency.⁶ Although some state of the art electrocatalysts for CO₂ electroreduction can produce CO and HCOOH at high selectivity (>80%) and energy efficiency (>60%), the selective production of higher hydrocarbons, especially oxygenates such as ethanol and methanol, is still lacking.⁷

In this talk, we will present examples of various catalysts for the selective electroreduction of CO₂ to oxygenates and hydrocarbons using an alkaline flow electrolyzer at ambient conditions. These catalysts include copper supported on metal oxides (Cu/M_xO_y), copper-based alloys, etc. Electroanalysis results of the Cu/M_xO_y catalysts include selective production of C₁ products (CO and methane) with traces of methanol when compared to copper nanoparticles. The copper-based alloys depict Faradaic efficiencies of up to 75% for C₂ products (ethylene and ethanol).

Acknowledgement

We gratefully acknowledge financial support from I2CNER and the SURGE Fellowship for UN.

References

1. Hansen J., Kharecha, P., et al., PLoS One, 2013.
2. Oerlemans, J., Science, 2005, 308(5722), 675-677.
3. https://www.eia.gov Accessed 05/29/2017.
4. R.M. Jhong, S. Ma, P.J.A. Kenis, Curr. Opin. Chem. Eng., 2013, 2, 191-199.
5. Ma, M. Sadakiyo, R. Luo, M. Heima, M. Yamauchi, P.J.A. Kenis, J. Power Sources, 2016, 301, 219-228.
6. L. Spath, D.C. Dayton, NREL/TP-510-34929, 2003.
7. J. Martin, G.O. Larrazabál, J. Pérez-Ramírez. Green Chem., 2015.