Tensile-Strained Cu Penetration Electrode Boosts Asymmetric C-C Coupling for Ampere-Level CO₂-to-C₂₊ Reduction in Acid

The synthesis of multicarbon (C₂₊) products remains a substantial challenge in sustainable CO₂ electroreduction owing to the need for sufficient current density and faradaic efficiency alongside carbon efficiency. Herein, we demonstrate ampere-level high-efficiency CO₂ electroreduction to C₂₊ products in both neutral and strongly acidic (pH=1) electrolytes using a hierarchical Cu hollow-fiber penetration electrode (HPE). High concentration of K⁺ could concurrently suppress hydrogen evolution reaction and facilitate C-C coupling, thereby promoting C₂₊ production in strong acid. By optimizing the K⁺ and H⁺ concentration and CO₂ flow rate, a faradaic efficiency of 84.5 % and a partial current density as high as 3.1 A cm^-2 for C₂₊ products, alongside a single-pass carbon efficiency of 81.5 % and stable electrolysis for 240 h were demonstrated in a strong acidic solution of H₂SO₄ and KCl (pH=1). Experimental measurements and density functional theory simulations suggested that tensile-strained Cu HPE enhances the asymmetric C-C coupling to steer the selectivity and activity of C₂₊ products.