Solar-Powered Asymmetric C-C Coupling toward Efficient CO₂-to-C₂₊ Hydrocarbon Conversion at Ultralow Bias

Electrochemical CO₂ reduction to multicarbon (C₂₊) hydrocarbons offers a promising route for value-added fuels and chemical feedstocks, yet its selectivity is usually limited by the sluggish symmetric C-C coupling. Herein, we demonstrate the synthesis of phosphidated Cu-Ni-Cu triangular single-atom cones (Ni₁PCu₂) by decorating Cu nanowires with Ni single atoms and P. These Ni₁PCu₂ can deliver an impressive CO₂-to-C₂₊ hydrocarbon (C₂H₄ 43%, C₂H₆ 48%) Faradaic efficiency of 91% under solar light at an ultralow bias of -0.3 V_RHE, and a stable C₂₊ hydrocarbon production rate of 370 μmol h^-1 cm^-2 for 4 days at 100 mA cm^-2, where the Cu nanowires harness solar light to generate plasmonic electrons for the CO₂ activation and its subsequent conversion to *CO, while electronegative phosphidation induces the formation of Cu⁺ sites to well stabilize *CO across high coverages. Strategically positioned Ni single atoms generate and confine active hydrogen (•H) for efficient hydrogenation of adjacent Cu⁺-*CO into Cu⁺-*CHO. The resulting Cu⁺-*CHO displays a weakened C-O bond and enhanced C nucleophilicity, allowing for solar-powered asymmetric C-C coupling with neighboring *CO toward efficient and selective C₂₊ hydrocarbon synthesis.