Tuning CuMgAl-Layered Double Hydroxide Nanostructures to Achieve CH4 and C2+ Product Selectivity in CO2 Electroreduction.

Electrochemical CO₂ reduction reaction (eCO₂RR) over Cu-based catalysts is a promising approach for efficiently converting CO₂ into value-added chemicals and alternative fuels. However, achieving controllable product selectivity from eCO₂RR remains challenging because of the difficulty in controlling the oxidation states of Cu against robust structural reconstructions during the eCO₂RR. Herein, we report a novel strategy for tuning the oxidation states of Cu species and achieving eCO₂RR product selectivity by adjusting the Cu content in CuMgAl-layered double hydroxide (LDH)-based catalysts. In this strategy, the highly stable Cu²⁺ species in low-Cu-containing LDHs facilitated the strong adsorption of *CO intermediates and further hydrogenation into CH₄. Conversely, the mixed Cu⁰/Cu⁺ species in high-Cu-containing LDHs derived from the electroreduction during the eCO₂RR accelerated C-C coupling reactions. This strategy to regulate Cu oxidation states using LDH nanostructures with low and high Cu molar ratios produced an excellent eCO₂RR performance for CH₄ and C₂₊ products, respectively.