Speaker
Description
Electrocatalytic conversion of CO$_2$ to higher order hydrocarbons has been proposed as one of the tools available to help mitigate the effects of anthropogenic climate change and create a carbon-neutral energy cycle.$^1$ The only pure metal that is capable of reducing CO$_2$ to C$^{2+}$ hydrocarbons is copper (Cu). However, it suffers from low selectivity towards these products.$^2$ Recent work in the literature has achieved high yields for C$^{2+}$ products at reasonable current densities$^{3-5}$, but a fundamental understanding of the nature of the catalytic active sites still remains elusive. Pristine, atomically flat ultra-high vacuum (UHV)-prepared Cu single crystal surfaces function as model catalysts and enable a better connection between experimental work and theoretical calculations. These surfaces were instrumental in work showing that atomically flat, defect-free, UHV-prepared copper surfaces favour the Hydrogen Evolution Reaction (HER) over the CO$_2$RR.$^6$ Only by introducing defects and high index sites with harsh treatments such as chemical etching were prevalent literature product distributions observed. In this study, atomically-flat, UHV-prepared Cu(111) surfaces were modified on the mesoscale, rather than the nanoscale, and show that introduction of small changes in surface structure at this length produce significant selectivity changes in CO$_2$RR. We show that despite careful control of the atomic structure on the surface, product selectivity varies dramatically from hydrogen to C$^{2+}$ hydrocarbons as the major product. We show that the mesoscopic structure of the surface is inducing these changes in product selectivity and thus, can further localize CO$_2$RR active sites.
References
1. Shih, C. F., Zhang, T., Li, J. & Bai, C. Powering the Future with Liquid Sunshine. Joule 2, 1925–1949 (2018).
2. Hori, Y. Electrochemical CO$_2$ Reduction on Metal Electrodes. Mod. Asp. Electrochem. 42, 89–189 (2008).
3. Xiao, C. & Zhang, J. Architectural Design for Enhanced C2Product Selectivity in Electrochemical CO$_2$Reduction Using Cu-Based Catalysts: A Review. ACS Nano (2021). doi:10.1021/acsnano.0c10697
4. García de Arquer, F. P. et al. CO$_2$ electrolysis to multicarbon products at activities greater than 1 A cm$^{-2}$. Science 367, 661–666 (2020).
5. Wang, X. et al. Efficient electrically powered CO$_2$-to-ethanol via suppression of deoxygenation. Nat. Energy 5, 478–486 (2020).
6. Scholten, F., Nguyen, K.-L. C., Bruce, J. P., Heyde, M. & Roldán Cuenya, B. Identifying structure‐selectivity correlations in the electrochemical reduction of CO$_2$: comparison of well‐ordered atomically‐clean and chemically‐etched Cu single crystal surfaces. Angew. Chemie Int. Ed. (2021). doi:10.1002/anie.202103102
