Multilayered Ti3C2 MXene-supported NiCoAl-LDH/g-C3N4 heterojunction with synergistic effect of Ni/Co/MXene for photocatalytic CO2 reduction to CO/CH4

• Fabrication of ternary g-C 3 N 4 /Ti 3 C 2 /NiCoAl-LDH nanocomposite for CO 2 reduction. • The combination of transition Ni and Co metal cations and one non-transition Al metal cation formed highly active LDH materials. • The formation of 2D/2D/2D S-scheme composite offered better electron-hole separation. • The Ti 3 C 2 MXene acted as an electron reservoir and scattering of g-C 3 N 4 and NiCoAl-LDH. A well-designed ternary nanostructure was developed that was comprised of multilayered Ti 3 C 2 MXene-assisted NiCoAl-LDH/g-C 3 N 4 2D/2D/2D S-scheme heterojunction. The NiCoAl-LDH is a highly active trimetallic layered double hydroxide (LDH) material with two transition Ni and Co metal cations and one non-transition Al-metal cation. The Ti 3 C 2 MXene is a multilayered nanotexture for promoting the interface interaction of g-C 3 N 4 with NiCoAl-LDH. The obtained g-C 3 N 4 /Ti 3 C 2 /NiCoAl-LDH nanomaterial was tested for photocatalytic CO 2 reduction with water. The photocatalytic CO 2 reduction resulted in excellent formation of CO and CH 4 with the production of 33.99 µmol and 3.70 µmol in 4 h, respectively, over the g-C 3 N 4 /Ti 3 C 2 /NiCoAl-LDH composite, much greater than pure samples. This enhanced photocatalytic activity was attributed to interfacial contact among g-C 3 N 4 , Ti 3 C 2 , and NiCoAl-LDH. The ternary metallic NiCoAl-LDH offered more active sites, quick charge carrier transport, and enhanced electronic conductivity. The S-scheme heterojunction between g-C 3 N 4 and NiCoAl-LDH improved charge carriers’ separation by providing an excellent pathway. The Ti 3 C 2 works as an electron reservoir, not only accumulating electrons from the S-scheme g-C 3 N 4 /NiCoAl-LDH for photocatalytic reduction but also working as a substrate for the distribution of NiCoAl-LDH and g-C 3 N 4 and offering reactive sites for the photocatalytic reduction of CO 2 with water. Stability analyses demonstrated the high durability of the g-C 3 N 4 /Ti 3 C 2 /NiCoAl-LDH nanocomposite over multiple cycles, supported by the robust structures of its three components.