Electron-Rich Pincer Ligand-Coupled Cobalt Porphyrin Polymer with Single-Atom Sites for Efficient (Photo)Electrocatalytic CO2 Reduction at Ultralow Overpotential

Porphyrin and phthalocyanine complexes bearing single-atom catalytic sites (M-N-4) have been explored as promising electrocatalysts for CO2 reduction reaction (CO2RR), 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 CO2RR. Herein, a novel N ' NN '-pincer-ligand (N-3)-coupled cobalt porphyrin (CoPor-N-3) polymer is developed for realizing efficient (photo)electrocatalytic CO2RR. The unraveled electronic structure and (photo)electrocatalytic features suggest that a synergistic effect between the electron-rich N-3 ligands and the Co-N-4 single-atom sites in the CoPor-N-3 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-N-3 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 CO2RR.

Automated summary

The development of a novel cobalt porphyrin polymer with synergistic effect between electron-rich N-3 ligands and Co-N-4 single-atom sites leads to more electron transfer to CO2 for its activation and reduction processes. The polymer exhibits good long-term durability and high efficiency in CO2 reduction with a low overpotential, showing promising potential for application.