(111) Facet‐oriented Cu₂Mg Intermetallic Compound with Cu₃‐Mg Sites for CO₂ Electroreduction to Ethanol with Industrial Current Density

Abstract

The efficient ethanol electrosynthesis from CO₂ is challenging with low selectivity at high CO₂ electrolysis rates, due to the competition with H₂ and other reduction products. Copper-based bimetallic electrocatalysts are potential candidates for the CO₂-to-ethanol conversion, but the secondary metal has mainly been focused on active components (such as Ag, Sn) for CO₂ electroreduction, which also promote selectivity of ethylene or other reduction products rather than ethanol. Limited attention has been given to alkali-earth metals due to their inherently active chemical property. Herein, we rationally synthesized a (111) facet-oriented nano Cu₂Mg (designated as Cu₂Mg(111)) intermetallic compound with high-density ordered Cu₃-Mg sites. The in situ Raman spectroscopy and density function theory calculations revealed that the Cu₃ ^- <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:semantics><mml:msub><mml:mrow></mml:mrow> <mml:msup><mml:mrow></mml:mrow> <mml:mi>δ</mml:mi></mml:msup> </mml:msub> <mml:annotation>$_{^{\rm{{\rm \delta} }} }$</mml:annotation> </mml:semantics> </mml:math> ^--Mg^- <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:semantics><mml:msub><mml:mrow></mml:mrow> <mml:msup><mml:mrow></mml:mrow> <mml:mi>δ</mml:mi></mml:msup> </mml:msub> <mml:annotation>$_{^{\rm{{\rm \delta} }} }$</mml:annotation> </mml:semantics> </mml:math> ⁺ active sites allowed to increase *CO surface coverage, decrease reaction energy for *CO-CO coupling, and stabilize *CHCHOH intermediates, thus promoting the ethanol formation pathway. The Cu₂Mg(111) catalyst exhibited a high FE_C2H5OH of 76.2±4.8 % at 600 mA⋅cm^-2, and a peak value of |j_C2H5OH| of 720±34 mA⋅cm^-2, almost 4 times of that using conventional Cu₂Mg with (311) facets, comparable to the best reported values for the CO₂-to-ethanol electroreduction.