Support-Induced Interfacial Effects Steer Methanol Selectivity in CO2 Electroreduction by Immobilized Cobalt Phthalocyanine.

Achieving product selectivity in multistep electrocatalysis requires delicately tuning the stability of key reaction intermediates to modulate the energetics of competing pathways. The conversion of CO2 by cobalt phthalocyanine (CoPc) presents a stark puzzle in this context; while solution-phase CoPc exclusively produces CO, its immobilization on carbon nanotube support triggers a substantial and unusual switch to methanol. Here, using multiscale simulations, we resolve this outstanding puzzle. We demonstrate that the carbon support is not a passive anchor but an active modulator of the catalytic environment. It functions by shielding one face of the CoPc molecule from the aqueous solvent, which substantially lowers the kinetic barrier for protonation while having little effect on CO desorption, thereby activating methanol production. Interfacial electric fields (EF) and cations further enhance this effect. Our findings establish support-induced desolvation as a new, rational design guideline for kinetically steering complex electrocatalytic reactions, providing a clear mechanistic basis for the unique reactivity of heterogenized molecular catalysts.