Beyond Molecular Dispersion: A Molecular-Cone Architecture of Cobalt Phthalocyanine on CNTs for Selective CO2 Electroreduction to Methanol

Abstract

Molecularly dispersed cobalt phthalocyanine (CoPc) on carbon nanotubes can be used as an efficient catalyst for electrochemical CO2-to-methanol conversion. However, increasing the CoPc loading to enhance the current density typically induces aggregation, which compromises methanol selectivity. To overcome this limitation, a CNT-supported nitro-substituted CoPc electrocatalyst (nCoPc@CNT) that adopts a distinct molecular-cone configuration was developed in this work, differing from both molecularly dispersed and aggregated structures. Structural analyses confirm that this molecular-cone configuration increases the density of electrochemically accessible sites while maintaining favorable catalytic activity. Combined theoretical and experimental analyses suggest that the molecular-cone architecture establishes an optimized interfacial microenvironment, in which the electric-field enhancement predicted by COMSOL is associated with local K+ enrichment and stabilization of the key *CO intermediate. Concurrently, interfacial water structures are reorganized to form a strengthened hydrogen bond network that promotes proton transport and accelerates *CO hydrogenation kinetics, as evidenced by a shortened DRT low-frequency relaxation time. Leveraging this microenvironment, the molecular-cone nCoPc@CNT catalyst achieves a methanol Faradaic efficiency of 64.4% at –0.98 V vs RHE and retains a Faradaic efficiency of 58.4% at 150 mA cm–2 in a membrane electrode assembly (MEA) cell. This work presents a microenvironment-engineering strategy for selective electrochemical CO2 reduction to methanol via cooperative interfacial tuning.