Dual Engineering of Lattice Strain and Valence State of NiAl-LDHs for Photoreduction of CO 2 to Highly Selective CH 4 .

Converting CO 2 to clean-burning fuel such as natural gas (CH 4 ) 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 (C 11 H 23 COONa, C 12 H 25 SO 4 Na, C 16 H 33 SO 4 Na) intercalated NiAl-layered double hydroxides (NiAl-LDH) is reported, resulting in the formation of LDH-S1 (S1 = C 11 H 23 COO - ), LDH-S2 (S2 = C 12 H 25 SO 4 - ) and LDH-S3 (S3 = C 16 H 33 SO 4 - ) with curved morphology. Compared with NiAl-LDH with a 1.53% selectivity of CH 4 , LDH-S2 shows higher selectivity of CH 4 (83.07%) and lower activity of HER (3.84%) in CO 2 photoreduction reaction (CO 2 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 CO 2 to CH 4 . 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 CH 4 . Therefore, the coupling effect of both lattice strain and electronic structure of the LDH-S2 significantly improves the activity and selectivity for CO 2 PR.