Br-Doped CuO Multilamellar Mesoporous Nanosheets with Oxygen Vacancies and Cetyltrimethyl Ammonium Cations Adsorption for Optimizing Intermediate Species and Their Adsorption Behaviors toward CO2 Electroreduction to Ethanol with a High Faradaic Efficiency.

It is a prospective tactic to actualize the carbon cycle via CO2 electroreduction reaction (CO2ER) into ethanol, where the crucial point is to design highly active and selective electrocatalysts. In this work, Br-doped CuO multilamellar mesoporous nanosheets with oxygen vacancies and cetyltrimethyl ammonium (CTA+) cations adsorption were synthesized on Cu foam by one-step liquid-phase method at room temperature. The nanosheets with numerous mesopores and rough edges provided abundant active sites for the adsorption of CO2 molecules and brought about a long retention time for intermediates. The dopant of Br- ions induced copious oxygen vacancies on CuO lattices, thereby reducing the activation energy of CO2 molecules and optimizing intermediate species and their adsorption behaviors, while adsorbed CTA+ cations modulated the O affinity of the Cu sites, favoring *OCH2CH3 intermediate converting to ethanol. The optimized Br1.95%-CuO can effectively catalyze CO2ER to C2H5OH in 0.1 M KHCO3. The faradaic efficiency of C2H5OH reached 53.3% with the partial current density of 7.1 mA cm-2 at a low potential of -0.6 V. In addition, after 14 h CO2ER test at -0.6 V, the current density and faradaic efficiency of C2H5OH on Br1.95%-CuO retained 99.6 and 93.9% of their original values, respectively, indicating its prominent catalytic stability. This work provided a novel strategy for designing a CuO catalyst by nonmetal doping and long-chain organic molecules adsorption with multiple active sites for optimizing intermediate species and their adsorption behaviors toward CO2ER to ethanol.

V-Doped Cu2 Se 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 *COB and its further hydrogenation to *COH, and, as such, the subsequent coupling of *COH and *COL eventually generates ethanol. As a result, the optimal Cu1.22 V0.19 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.