CO₂RR-to-CO Enhanced by Self-Assembled Monolayer and Ag Catalytic Interface

Electroreduction of CO2 to fuels (e.g., CO) catalyzed by transition metal catalysts is a promising approach to mitigate global warming issues, but it has limitations of low catalytic activity and high applied potential. The interface between self-assembled monolayers (SAMs) and transition metal surfaces could potentially stabilize the active surfaces and create bifunctional catalytic sites to improve the catalytic performance. Herein, we proposed a new type of electrocatalyst, 4-mercaptobenzonitrile (4-MBN) SAMs-modulated Ag, as an example to enhance the reaction of CO2-to-CO over Ag. We first examined the stabilization effect of 4-MBN SAMs over Ag and then evaluated the CO2-to-CO over 4-MBN/Ag (i.e., Ag(111), Ag(100), and Ag(211)) using density functional theory calculations. Our results showed that 4-MBN SAMs strongly bonded over Ag(211), and hence stabilized the Ag step site, the potential active site for the CO2-to-CO reaction. Notably, 4-MBN SAMs introduced new organic active sites. The new organic active sites mitigated the formation free energy of the key intermediate *OCOH (the potential rate-limiting step of CO2-to-CO) via a strong C–N bond up to 0.65 eV, compared to that of the pristine Ag surface. Consequently, CO2-to-CO can possibly occur at a lower applied potential at the SAM/Ag interface than that over the pristine Ag surface. Overall, our theoretical work demonstrates that a SAMs/metal interface stabilizes step sites, creates dual organic–inorganic active sites, modifies surface electronic properties, and provides a new strategy for the electrocatalyst design with potentially enhanced energy efficiency.