Fig. 2: Enhanced CO₂RR performance, mechanism and kinetics of BOC-Li.

a Potential-dependent FE of formate using an H cell in CO₂-saturated 0.5 M KHCO₃ (pH = 7.27 ± 0.04, n = 3) for BOC-Li and BOC with mass loading as 1 mg cm⁻². The CO₂ flow rate was 20 sccm at room temperature. All potentials reported are non-iR corrected. The error bars represent standard deviations from three independent measurements. b Nyquist plots demonstrating the reduced charge transfer resistance of BOC-Li (R_s = 3.8 ± 0.2 Ω, n = 3) relative to BOC (R_s = 3.4 ± 0.3 Ω, n = 3) at −0.27 V in H-cell. All potentials reported are non-iR corrected. c The 64.0 mV/dec⁻¹ Tafel slope on Li-doped catalyst versus 85.7 mV/dec⁻¹ on BOC indicates a concerted proton-electron transfer pathway. d Formate yield decreases with higher ²H₂O content, showing a deuterium KIE that identifies proton transfer as rate-determining. e, f In situ ATR-SEIRAS shows potential-dependent *OCHO intermediate (1438, 1600 cm⁻¹) only on BOC-Li, validating its facilitated proton-coupled electron transfer. The mass loading was 2 mg cm⁻². Source data are provided as a Source Data file.