Porphyrin and phthalocyanine complexes bearing single-atom catalytic sites (M-N4 ) have been explored as promising electrocatalysts for CO2 reduction reaction (CO2 RR), whose activity can be improved by regulating the ligands and/or the metal centers. Moreover, their photosensitive features also provide the possibility for highly efficient photoelectrocatalytic CO2 RR. Herein, a novel N'NN'-pincer-ligand (N3 )-coupled cobalt porphyrin (CoPor-N3 ) polymer is developed for realizing efficient (photo)electrocatalytic CO2 RR. The unraveled electronic structure and (photo)electrocatalytic features suggest that a synergistic effect between the electron-rich N3 ligands and the Co-N4 single-atom sites in the CoPor-N3 polymer results in the Co centers attaining more electrons, which is beneficial to facilitating the electron transfer to CO2 for the activation and reduction processes. As expected, the resultant CoPor-N3 polymer delivers a good long-term durability and high CO faradaic efficiency (96%) at an ultralow overpotential (0.39 V), which outperforms the CoPor alone and most porphyrin-/phthalocyanine-based electrocatalysts reported so far. Moreover, the photosensitivity of CoPor units can further reduce the overpotential to 0.34 V with a CO faradaic efficiency over 90% under light illumination. The present findings offer a new approach to constructing porphyrin-based photosensitive electrocatalysts with high-efficiency photoelectrocatalytic CO2 RR.
Keywords: CO 2 reduction reaction; N′NN′-pincer ligands; cobalt porphyrin polymers; electrocatalysts; photoelectrocatalysis.
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