Space-Confined Molecular Catalysis toward Electrocatalytic CO2 Reduction on Metal Phthalocyanine@Nitrogen-Doped Carbon Nanosheet

Abstract

Phthalocyanines have emerged as attractive materials for electrocatalytic carbon dioxide reduction. However, the challenge of finding a support that is stable while maintaining catalytic activity and loading remains elusive. Porous carbon materials are considered reliable substrates for supporting molecular catalysts. Herein, a nitrogen-rich carbon nanosheet (NiPc/NMCN) with multilayer and mesoporous structure is synthesized based on a kinetically controlled self-assembly strategy and used for phthalocyanine loading. The multilayer composite structure of NMCN guides the molecular-scale dispersion of phthalocyanine and plays a crucial role in its catalytic process. Moreover, the phthalocyanine molecules retain their metal-N₄ structure after impregnation. Therefore, the remarkable CO₂ electroreduction properties of phthalocyanine are fully demonstrated. At −0.73 V vs. RHE, NiPc/NMCN achieves the highest CO faradaic efficiency (FE_CO) of 96.0%. Meanwhile, current densities in membrane electrode module electrolyzers can reach industrial amperage levels, while the FEco remains at 60% at 880 mA cm^–2. Density functional theory (DFT) indicates that the high performance of NiPc/NMCN is attributed to the significant reduction of the CO₂RR energy barrier. Phthalocyanines restricted by the porous carbon could produce the intermediate *COOH more rapidly, determining high CO₂RR selectivity, which is confirmed by in situ (FTIR) spectroscopy. Consequently, the strategy of constructing confined multilayer mesoporous carbon structures provides an avenue for the design of efficient CO₂ reduction molecular catalysts.