Synergistic Effects in NiMnEr-LDH: d-d-f Orbital Overlap Enables Efficient CO 2 Photoreduction

Abstract

To achieve high selectivity in photocatalytic CO2 reduction (CO2PR), developing ternary layered double hydroxide (LDH) photocatalysts through a simple method is essential. Herein, Er introduction modulates the orbital energies of metal constituents, enhancing unsaturated active sites and forming highly active NiMnEr-LDH. This promotes photogenerated carrier separation and improves reducibility. Under visible light (λ > 400 nm), NiMnEr-LDH achieves a CO production rate of 1403.72 μmol•g -1 •h -1 -about 12 times that of pristine NiMn-LDH-with 96.87% CO selectivity. Structural and photoelectrochemical analyses reveal that Er incorporation not only preserves the defect-rich monolayer configuration but also promotes the formation of Ni 2+ and Mn 3+ , creating synergistic metal active sites. The in situ DRIFTS and theoretical calculations demonstrated that Er induces d-d-f orbital overlap among the metals, lowering the energy barrier of the *COOH formation step (0.33 eV) and enabling highly active and selective CO generation. This work provides new insights into efficient photocatalytic CO2 reduction by modulating the orbital structure of LDH layers using rare-earth elements with forbital.