(478g) Hybrid Organic-Inorganic Interfaces Drive CO2 Reduction to C2 hydrocarbons

To mitigate the excess atmospheric CO₂ sustainably, one promising way is CO₂ electroreduction reaction into valuable C₂ products (CO₂RR-to-C₂) such as ethanol and ethylene using renewable electricity.¹ Cu is considered to be the most ideal pure metal catalyst for CO₂RR-to-C₂ but suffers from high overpotentials and low selectivity of C₂ species.

To reduce the overpotentials and enhance the selectivity of CO₂RR-to-C₂ over Cu, we designed a hybrid organic-inorganic interface between aminothiolate self-assembled monolayer (SAM) and Cu catalyst.² In particular, we studied the electrocatalytic performance of CO₂RR-to-C₂ via varying the carbon chain lengths and configurations of aminothiolate SAMs (Figure 1a). Our results show that: (1) aminothilate SAMs prefers lying-down over the Cu surface at a low coverage (1/16 and 2/16 monolayer (ML)), while it favors standing-up over the surface at a high coverage (4/16, 8/16 ML) due to the lateral interactions; (2) under the electroreduction condition (pH = 13, U_SHE = -1.0 V), aminothiolates at 8/16 ML are unstable and prone to be reduced to thiols and desorb into solution (Figure 1b); (3) the aminothiolate SAM with longer carbon chain lengths is more stable (Figure 1b); and (4) a low coverage of SAM with lying-down structure creates hybrid organic-inorganic active sites for stabilizing C₂ intermediate, while a high coverage of SAM with standing-up structure induces confinement space effect for enlarging the adsorption energy difference of CO^* and COH^*. Both lying-down and standing-up aminothiolate SAMs decrease the activation barriers and reaction energies of C-C coupling (rate-limiting step of CO₂RR-to-C₂ over Cu) (Figure 1c). Overall, this study leads to a new type of electrocatalysts – hybrid organic-inorganic interfaces.

References

1. Li, J.; Ozden, A.; Wan, M. et al., Nat. Commun. 2021, 12 (1), 2808.

2. Wan, M.; Gu, Z.; Che, F., ChemCatChem 2021, 14 (4), e202101224.