Fig. 1. Schematic illustration of the self-optimizing CO2-to-DMC electrocatalytic system enabled by in-situ Pd capture and pyrrolic-N sites.

Fig. 2. Synthetic procedure for the NC-PILs material.

Fig. 3. SEM images of NC-PVimBF4 (a‒c), NC-PVimPF6 (d‒f), NC-PVimCN (g‒i), and NC-PVimBr (j‒l).

Fig. 4. Characterization of XRD patterns (a), Raman spectra (b), high-resolution XPS spectra of the N 1s region (c) and content of pyridine N and pyrrole N (d) of NC-PILs.

Fig. 5. High-resolution Br 3d XPS spectra of NC-PVimBr (a), N 1s XPS spectra of NC-PVimBr and NC-PVimCN calcined under temperatures of 400 °C (b), 600 °C (c), and 900 °C (d) and percentage content of pyridine N and pyrrole Nat 400, 600, and 900 °C (e).

Fig. 6. Schematic of the NC-PVimBr formation derived by PIL.

Fig. 7. Characterizations of Pd/AC by TEM images (a), HR-TEM images (b,c), high-resolution Pd 3d XPS spectra (d) and N2 adsorption-desorption isotherms with pore size distribution (e).

Fig. 8. Electrochemical performance of NC-PIL. (a) DMC FE for different substrate materials. (b) DMC FE of NC‑PVimBr at potentials ranging from -1.8 to -2.1 V vs. Ag/AgCl. (c) DMC FE under different Pd/AC catalyst loadings. (d) DMC FE over multiple consecutive cycles. (e) Long‑term stability test of DMC FE. (f) Stability test performed at a constant current density of 12 mA cm‒2 in single cell.

Fig. 9. Control experiments with and without Pd/AC in both single-cell and H-cell configurations (Electrolyte: 0.1 mol L‒1 NaBr in CH3OH).

Fig. 10. TEM and HRTEM images of the cathode after reaction (a‒c) and TEM-EDS images of the cathode after reaction (d‒g).

Fig. 11. High-resolution XPS spectra of the Pd 3d region (a), Pd deposition amount over time (b), Pd content in electrolyte solution and on cathode with different Pd-based catalysts (c), the temporal evolution of FE for H2 and CO (d), FECO versus Pd deposition amount (e), andLSV of NC-PVimBr and Pd-NC-PVimBr in CO2-saturated 0.1 mol L‒1 NaBr-CH3OH in H-type cells for electrocatalytic CO2RRs (f).

Fig. 12. CO2RR pathways and theoretical calculations: pathway on Pd-C (a), pathway on C-pyridinic N-Pd (Pd-Py) (b), pathway on C-pyrrolic N-Pd (Pd-Pr) (c), adsorption energies of Pd on C, pyridinic N, and pyrrolic N (d), and Gibbs free energies over Pd-C, Pd-Py, and Pd-Pr (e).

Fig. 13. Charge density difference plots and Bader charge analysis for the three catalyst models. (a-c) Side view and top view of the bare Pd-support systems for Pd-C, Pd-Py, and Pd-Pr, with the corresponding electron transfer from the Pd cluster. (d-f) Side view and top view of the CO2-adsorbed systems (Pd-C-CO2*, Pd-Py-CO2*, and Pd-Pr-CO2*), with the corresponding charge transfer to CO2. Yellow and cyan isosurfaces represent electron accumulation and depletion, respectively.

Fig. 14. Proposed reaction pathways for CH3OH dissociation and related energies on Pd-C (a), on Pd-Py (b), on Pd-Pr (c). Adsorption energy of CO2 and dissociation energy of CH3OH (d) for H* formation on Pd-C, Pd-Py, and Pd-Pr.

Fig. 15. In-situ ATR-FTIR spectra collected on the NC-PVimBr electrode with in situ electrodeposited Pd species in CO2-saturated 0.1 mol L‒1 NaBr methanol electrolyte at applied potentials from -1.5 to -2.2 V vs. Ag/AgCl.

Fig. 16. Possible reaction mechanism of the electrocatalytic synthesis of DMC.