A crystal growth kinetics guided Cu aerogel for highly efficient CO₂ electrolysis to C₂₊ alcohols

To realize commercial CO₂ electrochemical reduction to C₂₊ alcohols, the selectivity and production rate should be further improved. Establishing controllable surface sites with a favorable local environment is an interesting route to guide the C₂₊ pathway. Herein, we report a room-temperature one-step synthetic strategy to fabricate a highly stable Cu aerogel as an efficient CO₂ reduction electrocatalyst. Controlling crystal growth kinetics using different reductants is an efficient strategy to modulate the nucleation and growth rate of Cu aerogels, enabling the creation of efficient surface sites for the C₂₊ pathway. Over the Cu aerogel obtained by reducing Cu²⁺ using a weak reductant (NH₃·BH₃), the faradaic efficiency of C₂₊ products could reach 85.8% with the current density of 800 mA cm^-2 at the potential of -0.91 V vs. reversible hydrogen electrode, and the C₂₊ alcohol selectivity was 49.7% with a partial current density of 397.6 mA cm^-2, while the Cu aerogel prepared using a strong reductant (NaBH₄) was favorable to generating CO. Experimental and theoretical studies showed that the selectivity of the reaction depended strongly on the desorption and dimerization of *CO intermediates on the catalysts. The strong reductant induced a defective Cu surface that could facilitate the desorption of the *CO intermediate, subsequently producing CO, whereas the low defect Cu produced using a weak reductant could significantly enhance the selectivity for the C₂₊ product by improving *CO adsorption and the C-C coupling on the catalyst. This work opens a new way for constructing efficient electrocatalysts for CO₂ electroreduction to C₂₊ alcohols.