Enhanced CO₂ Reduction on a Cu-Decorated Single-Atom Catalyst via an Inverse Sandwich M-Graphene-Cu Structure

The highly active and selective electrochemical CO₂ reduction reaction (CO₂RR) can be exploited to produce valuable chemicals and fuels and is also crucial for achieving clean energy goals and environmental remediation. Decorated single-atom catalysts (D-SACs), which feature synergistic interactions between the active metal site (M) and an axially decorated ligand, have been extensively explored for the CO₂RR. Very recently, novel double-atom catalysts (DACs) featuring inverse sandwich structures were theoretically proposed and identified as promising CO₂RR electrocatalysts. However, the experimental synthesis of DACs remains a challenge. To facilitate the fabrication and to realize the potential of these novel DACs, we designed a D-SAC system, denoted as M₁@gra+Cu_slab. This system features a graphene layer with a vacancy-anchored SAC, all stacked on a Cu(111) surface, thereby embodying a Cu slab-supported inverse sandwich M-graphene-Cu structure. Using density functional theory calculations, we evaluated the stability, selectivity, and activity of 27 M₁@gra+Cu_slab systems (M = Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Y, Zr, Nb, Mo, Ru, Rh, Pd, Ag, Cd, Hf, Ta, W, Re, Os, Ir, Pt, or Au) and showed five M₁@gra+Cu_slab (M = Co, Ni, Cu, Rh, or Pd) systems exhibit optimal characteristics for the CO₂RR and can potentially outperform their SAC and DAC counterparts. This study offers a new strategy for developing highly efficient CO₂RR D-SACs with an inverse sandwich structural moiety.