CO2 Activation on Single-Atom Catalysts: Importance of the Supporting Matrix

Single-Atom Catalysis (SACs) is an emerging frontier with significant potential to bridge the gap between homogeneous and heterogeneous catalysis. Among various chemical processes of interest, the reduction of CO2 (CO2RR) into valuable chemicals has garnered particular attention. The analogy between SACs and coordination chemistry compounds has highlighted the importance of the supporting matrix. In this study, we explored CO2 activation on SACs using density functional theory (DFT) calculations. Our analysis focused on nine transition metals (Fe, Co, Ni, Ru, Rh, Pd, Os, Ir, Pt) and three distinct support materials: nitrogen-doped graphene (4N-Gr), a gold surface (Au(111)), and titanium nitride (TiN), an emerging material with unique properties. Our findings indicate that CO2 activation on SACs is generally challenging, often requiring dual active centers. SACs based on 4N-Gr and Au(111) showed limited ability to bind CO2 molecules. Conversely, TiN emerged as a highly promising support, effectively promoting CO2 activation. This capability stems from the formation of bidentate adducts involving both the dopant and a surface titanium atom of the matrix. Furthermore, TiN-based SACs demonstrated the ability to favour *CO*OH adduct formation (* indicates an adsorbed species) over *COOH or *OCHO during the first electrochemical reduction step, showcasing enhanced reactivity. These results underscore the potential of TiN as a robust support material for SACs in CO2RR, offering new perspectives for efficient CO2 conversion.