Metal Ion Cycling of Cu Foil for Selective C-C Coupling in Electrochemical CO2 Reduction

Electrocatalytic CO 2 reduction to higher value hydrocarbons beyond C 1 products is desirable for applications in energy storage, transportation, and the chemical industry. Cu catalysts have shown the potential to catalyze C-C coupling for C 2+ products, but still suffer from low selectivity in water. 1 Here we use density functional theory to determine the energetics of the initial C-C coupling steps on different Cu facets in CO 2 reduction, and suggest that the Cu(100) and stepped (211) facets favor C 2+ product formation over Cu(111). To demonstrate this we report the tuning of facet exposure on Cu foil through the metal ion battery cycling method. Compared to the polished Cu foil, our 100-cycled Cu nanocube catalyst with (100) facets exposed presents a 6-fold improvement in C 2+ to C 1 product ratio, with a highest C 2+ Faradaic efficiency of over 60 % and H 2 below 20 %, and a corresponding C 2+ current of more than 40 mA/cm 2 . 2 References: (1) Hori, Y., Takahashi, I., Koga, O. & Hoshi, N. J. Mol. Catal. A Chem. 199 , 39-47 (2003). (2) Jiang, K., Sandberg, R.B., Akey, A.J., Liu, X., Bell, D.C., Nørskov, J.K., Chan, K. & Wang, H. Nat. Catal. in press (2018).