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

Abstract 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 CO 2 (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 CO 2 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 CO 2 activation on SACs is generally challenging, often requiring dual active centers. SACs based on 4N-Gr and Au(111) showed limited ability to bind CO 2 molecules. Conversely, TiN emerged as a highly promising support, effectively promoting CO 2 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 CO 2 conversion.