(653b) Elucidating the Influence of Electric Fields Toward CO2 Activation on YSZ(111)

Despite its high thermodynamic stability, the presence of a negative electric field is known to facilitate the activation of CO₂ through electrostatic effects.¹ To utilize electric fields for a reverse water gas shift reaction, it is critical to elucidate the role of an electric field on a catalyst surface toward activating a CO₂ molecule. A first-principles study was conducted to gain an atomic and electronic description of CO₂ when adsorbed upon YSZ (111) surfaces when external electric fields of +1V/Å, 0 V/Å, and -1 V/Å are applied. We have found that the application of an external electric field generally causes destabilization of the oxide bonds, displaying higher reducibility. Surface reducibility was the highest when positive charges accumulate on the surface, i.e. when a positive electric field is applied. Interestingly, our findings also show that the presence of a positive field or in the absence of an electric field leads to the physisorption of CO₂ with a preferential coordination to the surface Y atom rather than to Zr. In contrast, CO₂ becomes chemisorbed in the presence of a negative electric field and bonds with surface O. In addition, a negative electric field leads to an accumulation of negative charge that bends CO₂, altering the shape and energy of its molecular orbitals, making C more electrophilic and enabling the formation of the CO₃^- complex.² Bond weakening was evident by the lengthening of the molecular C-O bonds and was investigated further in a vibrational mode analysis. The catalyst surface thus facilitates CO₂ activation mainly through a charge transfer pathway. A fundamental understanding of how CO₂ interacts with a field-induced surface allows us to fine-tune the environment suitable for facilitating CO₂ cleavage to make value-added products.

References

1. J. Phys. Chem. Lett. 1, 3256–3260 (2010).
2. ChemPhysChem 18, 3135–3141 (2017).