Theoretical study on electrocatalytic carbon dioxide reduction over copper with copper-based layered double hydroxides

The conversion of CO₂ into valuable fuels and multi-carbon chemical substances by electrical energy is an effective strategy to solve environmental problems by using renewable energy sources. In this work, the density functional theory (DFT) method is used to reveal the electrocatalytic mechanism of CO₂ reduction reaction (CO₂RR) over the surface of CuAl-Cl-layered double hydroxides (LDHs) with Cu monoatoms (Cu@CuAl-Cl-LDH), Cu₂ diatoms (Cu₂@CuAl-Cl-LDH), orthotetrahedral Cu₄ clusters (Td-Cu₄@CuAl-Cl-LDH) and planar Cu₄ clusters (Pl-Cu₄@CuAl-Cl-LDH). The active sites, density of states, adsorption energy, charge density difference and free energy are calculated. The results show that CO₂RR over all the above five catalysts can generate C₂ products. Pl-Cu₄@CuAl-Cl-LDH tends to generate C₂H₅OH, while the remaining four structures all tend to produce C₂H₄. Cu^δ+ favors CO₂RR, and Td-Cu₄@CuAl-Cl-LDH with a larger positively charged area at the active site has the better electrocatalytic performance among the calculated systems with a maximum step height of 0.78 eV. The selectivity of the products C₂H₄ and C₂H₅OH depends on the dehydration of the intermediate *C₂H₂O to *C₂H₃O or *CCH; if the dehydration produces *CCH intermediate, the final product is C₂H₄, and if no dehydration occurs, C₂H₅OH is produced. This work provides theoretical information and guidance for further rational design of efficient CO₂RR catalysts for energy saving and emission reduction.