V‐Doped Cu2Se Hierarchical Nanotubes Enabling Flow‐Cell CO2 Electroreduction to Ethanol with High Efficiency and Selectivity

CO₂ electrocatalytic reduction (CO₂ ER) to multicarbon (C₂₊ ) products is heavily pursued because of their commercial values, and the efficiency and selectivity have both attracted tremendous attention. A flow-cell is a device configuration that can greatly enhance the conversion efficiency but requires catalysts to possess high electrical conductivity and gas permeability; meanwhile, the catalysts should enable the reaction pathway to specific products. Herein, it is reported that V-doped Cu₂ Se nanotubes with a hierarchical structure can be perfectly compatible with flow-cells and fulfil such a task, achieving CO₂ electroreduction to ethanol with high efficiency and selectivity. As revealed by the experimental characterization and theoretical calculation, the substitutional vanadium doping alters the local charge distribution of Cu₂ Se and diversifies the active sites. The unique active sites promote the formation of bridge *CO_B and its further hydrogenation to *COH, and, as such, the subsequent coupling of *COH and *CO_L eventually generates ethanol. As a result, the optimal Cu_1.22 V_0.19 Se nanotubes can electrocatalyze CO₂ to ethanol with a Faradaic efficiency of 68.3% and a partial current density of -207.9 mA cm^-2 for the single liquid product of ethanol at -0.8 V in a flow-cell. This work provides insights into the materials design for steering the reaction pathway toward C₂₊ products, and opens an avenue for flow-cell CO₂ ER toward a single C₂₊ liquid fuel.