Electrochemical CO₂ reduction to multicarbon products faces challenges of unsatisfactory selectivity, productivity, and long-term stability. Herein, we demonstrate CO₂ electroreduction in strongly acidic electrolyte (pH ≤ 1) on electrochemically reduced porous Cu nanosheets by combining the confinement effect and cation effect to synergistically modulate the local microenvironment. A Faradaic efficiency of 83.7 ± 1.4% and partial current density of 0.56 ± 0.02 A cm⁻², single-pass carbon efficiency of 54.4%, and stable electrolysis of 30 h in a flow cell are demonstrated for multicarbon products in a strongly acidic aqueous electrolyte consisting of sulfuric acid and KCl with pH ≤ 1. Mechanistically, the accumulated species (e.g., K⁺ and OH⁻) on the Helmholtz plane account for the selectivity and activity toward multicarbon products by kinetically reducing the proton coverage and thermodynamically favoring the CO₂ conversion. We find that the K⁺ cations facilitate C-C coupling through local interaction between K⁺ and the key intermediate *OCCO.

电化学 CO ₂还原为多碳产品面临着选择性、生产率和长期稳定性不尽如人意的挑战。在此，我们通过结合限制效应和阳离子效应协同调节局部微环境，在电化学还原的多孔 Cu 纳米片上展示了强酸性电解质 (pH ≤ 1) 中的 CO _{2电还原。}多碳产品在强酸性水溶液中的法拉第效率为 83.7 ± 1.4%，部分电流密度为 0.56 ± 0.02 A cm ^-2，单程碳效率为 54.4%，并且在流通池中稳定电解 30 小时由 pH ≤ 1 的硫酸和 KCl 组成的电解质。从机械上讲，积累的物质（例如，K ⁺和 OH ^{- ) 在亥姆霍兹平面上通过动力学降低质子覆盖率和热力学有利于 CO} ₂转化来解释对多碳产物的选择性和活性。我们发现 K ^{+阳离子通过 K +}和关键中间体 *OCCO之间的局部相互作用促进 CC 偶联。