Dual Engineering of Lattice Strain and Valence State of NiAl‐LDHs for Photoreduction of CO₂ to Highly Selective CH₄

Abstract

Converting CO₂ to clean-burning fuel such as natural gas (CH₄ ) with high activity and selectivity remains to be a grand challenge due to slow kinetics of multiple electron transfer processes and competitive hydrogen evolution reaction (HER). Herein, the fabrication of surfactants (C₁₁ H₂₃ COONa, C₁₂ H₂₅ SO₄ Na, C₁₆ H₃₃ SO₄ Na) intercalated NiAl-layered double hydroxides (NiAl-LDH) is reported, resulting in the formation of LDH-S1 (S1 = C₁₁ H₂₃ COO^- ), LDH-S2 (S2 = C₁₂ H₂₅ SO₄ ^- ) and LDH-S3 (S3 = C₁₆ H₃₃ SO₄ ^- ) with curved morphology. Compared with NiAl-LDH with a 1.53% selectivity of CH₄ , LDH-S2 shows higher selectivity of CH₄ (83.07%) and lower activity of HER (3.84%) in CO₂ photoreduction reaction (CO₂ PR). Detailed characterizations and DFT calculation indicates that the inherent lattice strain in LDH-S2 leads to the structural distortion with the presence of V_Ni/Al defects and compressed MOM bonds, and thereby reduces the overall energy barrier of CO₂ to CH₄ . Moreover, the lower oxidation states of Ni in LDH-S2 enhances the adsorption of intermediates such as OCOH* and *CO, promoting the hydrogenation of CO to CH₄ . Therefore, the coupling effect of both lattice strain and electronic structure of the LDH-S2 significantly improves the activity and selectivity for CO₂ PR.