(5b) Effect of Interfacial Electric Field on Electrochemical CO2 Reduction to Multicarbon Products

The electrochemical CO₂ reduction reaction (CO₂RR) is a promising approach to close the carbon cycle by converting CO₂ to high-value chemicals and fuels. Past reports have shown that modulating the electric field at the electrode-electrolyte interface can influence the selectivity of CO₂RR by tuning the kinetics and thermodynamics of key elementary steps.^1,2 One strategy to modulate this interfacial electric field involves introducing an additive molecular layer on the metal catalyst surface, leveraging electrostatic interactions and dielectric effects.² The resulting hybrid catalyst with a rich metal-additive interface has been shown to enhance CO production, stabilize key intermediates, and promote C-C coupling.^3–6 However, the atomic-scale interactions between the metal and additive layer, as well as the effect of the additive layer on the interfacial electric field at the metal-additive interface, remains unclear.

In this study, a model interface comprising copper (Cu) and cobalt phthalocyanine (CoPc) was prepared to investigate the potential dependent interfacial electric field using in situ surface-enhanced Raman spectroscopy and grand-canonical density functional theory (GC-DFT) calculations. Our findings reveal that CoPc attenuates the electric field at the Cu-CoPc interface compared to a bare Cu surface. Electrolysis experiments show that CoPc-modified Cu catalyst exhibits an enhanced selectivity towards multicarbon (C₂₊) products relative to bare Cu. Complimentary GC-DFT further corroborates that CoPc decreases the magnitude of the electric field, which in turn lowers the energy barrier for the C-C coupling step. These insights underscore the potential of interfacial electric field modulation as a strategy to enhance the selective C₂₊ production of the Cu catalyst during CO₂RR.

References:

(1) ACS Catal. 2016, 6 (10), 7133–7139

(2) Chem Catalysis 2022, 2 (9), 2229–2252.

(3) Nat. Nanotechnol. 2024, 19 (3), 311–318.

(4) Journal of Energy Chemistry 2024, 92, 499–507.

(5) Nat Catal 2019, 3 (1), 75–82.

(6) Nano Lett. 2022, 22 (9), 3801–3808.