Electrocatalytic CO₂ reduction to higher value hydrocarbons beyond C₁ 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 C₂₊ 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 CO₂ reduction, and suggest that the Cu(100) and stepped (211) facets favor C₂₊ 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 C₂₊ to C₁ product ratio, with a highest C₂₊ Faradaic efficiency of over 60 % and H₂ below 20 %, and a corresponding C₂₊ current of more than 40 mA/cm².²

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).