(686e) Demonstration of One-Pot Tandem Catalysis for Electrochemical CO2 Reduction to CH4 Using Both Quantum Mechanics and Experiment

The electrochemical conversion of CO₂ into value-added chemicals, such as carbon monoxide, hydrocarbons and alcohols, using renewable energy sources provides a promising strategy to alleviate environmental problems caused by the greenhouse effect¹. To achieve this, a sustainable and efficient catalyst which operates at low potential bias is in great need. Many catalysts are able to reduce CO₂ to CO with high efficiency. However, only Cu shows mediocre activities in producing further reduced products such as methane and ethylene^2-5. CO₂ electroreduction on Cu was confirmed to involve reduction to a CO adsorbate followed by reduction to hydrocarbons and oxygenates^6-9. Simultaneous optimization of these processes over a single reaction site is challenging due to linear scaling correlation of the binding strength to key intermediates.

Herein we report both computational and experimental investigations of electrochemical CO₂ reduction on a well-defined model surface constructed with Cu and CO-productive materials (i.e. Au and Ag). The separation of reaction sites for CO₂ reduction to CO as well as its subsequent reductions allows for the concurrent improvement for both processes. We found that the CO produced by Au or Ag would migrate to Cu with low activation energy and reduced further by Cu. Also, we proved that sufficient CO supply to Cu surface is critical for methane and ethylene production. Compared to a bare Cu surface, our results showed a better CH₄ selectivity and activity over hydrogen evolution reaction (HER) with the introduction of CO-productive materials^{10, 11}. Such enhancement is attributed to the abundance of CO on Cu surface provided by Au or Ag which is supported by both computational and experimental evidences. Based on these results, discussions on mechanism understandings and catalyst design principles are made for achieving more advanced CO₂ electroreduction performance.

1 Q. Lu and F. Jiao, Nano Energy, 2016, 29, 439-456.

2 Y. Hori, K. Kikuchi and S. Suzuki, Chem. Lett., 1985, 14, 1695-1698.

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

4 Y. Hori, in Modern Aspects of Electrochemistry, eds. C. G. Vayenas, R. E. White and M. E. Gamboa-Aldeco, Springer New York, New York, NY, 2008, DOI: 10.1007/978-0-387-49489-0_3, pp. 89-189.

5 K. P. Kuhl, T. Hatsukade, E. R. Cave, D. N. Abram, J. Kibsgaard and T. F. Jaramillo, J. Am. Chem. Soc., 2014, 136, 14107-14113.

6 A. A. Peterson, F. Abild-Pedersen, F. Studt, J. Rossmeisl and J. K. Nørskov, Energy Environ. Sci., 2010, 3, 1311.

7 A. A. Peterson and J. K. Nørskov, J. Phys. Chem. Lett., 2012, 3, 251-258.

8 Y. Hori, A. Murata, R. Takahashi and S. Suzuki, J. Am. Chem. Soc., 1987, 109, 5022-5023.

9 Y. Hori, A. Murata and Y. Yoshinami, J. Chem. Soc., Faraday Trans., 1991, 87, 125-128.

10 K. P. Kuhl, E. R. Cave, D. N. Abram and T. F. Jaramillo, Energy Environ. Sci., 2012, 5, 7050.

11 Y. Hori, A. Murata and R. Takahashi, Journal of the Chemical Society, Faraday Transactions 1: Physical Chemistry in Condensed Phases, 1989, 85, 2309-2326.