The Significance of the 'Insignificant': Non-covalent Interactions in CO₂ Reduction Reactions with 3C-TM (TM=Sc-Zn) Single-Atom Catalysts

With energy shortages and excessive CO₂ emissions driving climate change, converting CO₂ into high-value-added products offers a promising solution for carbon recycling. We investigate CO₂ reduction reactions (CO₂RR) catalyzed by 10 single-atom catalysts (SACs), incorporating weak non-covalent interactions, specifically lone pair-π and H-π interactions. The SACs, consisting of transition metals coordinated by three carbon atoms in a defective graphene substrate (3C-TM, TM=Sc-Zn), leverage these interactions to influence the energy fluctuations of intermediates and the limiting potentials of CO₂RR, without altering the overall reaction pathway. Our findings show that SACs based on early transition metals (Sc, Ti, V, Cr) can serve as catalysts for C₁ products, including HCOOH, HCHO, CH₃OH, and CH₄, while those based on Fe and Co are suitable for CO formation. Driving force analysis helps bridge theoretical results with experimental observations and propose a modified approach for assessing hydrogen evolution reactions (HER) competition. SACs based on Ni and Cu exhibit moderate HER tolerance, while early transition metals excel in selective CO₂ reduction. We also identify a linear scaling relationship between the free energies of *COOH and *CO. This study offers valuable insights for future experimental studies and large-scale computational screenings.