Enhancing proton-coupled electron transfer for electrochemical CO2 reduction to MeOH

Electrochemical CO2 reduction to methanol requires multiple proton-coupled electron-transfer (PCET) steps, but controlling proton delivery to catalytic intermediates remains challenging. Here, we regulate interfacial proton transfer by modifying cobalt phthalocyanine/carbon nanotube catalysts with protic ionic liquids (ILs). Methanol turnover exhibits a volcano-type dependence on 5 IL pKa, with maximum activity at pKa ~8-10. Kinetic isotope and isotope-labeling measurements implicate IL cations as local proton donors, while electrochemical measurements link methanol activity to protonation of the phthalocyanine ligand. In situ ATR-SEIRAS reveals IL-dependent restructuring of interfacial water and depletion of bridge-bound CO as methanol activity increases, consistent with accelerated conversion of CO-derived intermediates. IL modification further 10 suppresses catalyst deactivation and enables methanol production during extended flow cell operation. These results show that tuning proton-donor acidity can control PCET and intermediate conversion during multistep CO2 electroreduction.