A Porphyrin/Graphene Framework: A Highly Efficient and Robust Electrocatalyst for Carbon Dioxide Reduction

Developing immobilized molecular complexes, which demonstrate high product efficiencies at low overpotential in the electrochemical reduction of CO2in aqueous media, is essential for the practical production of reduction products. In this work, a simple and facile self-assembly method is demonstrated by electrostatic interaction and π-π stacking for the fabrication of a porphyrin/graphene framework (FePGF) composed of Fe(III) tetraphenyltrimethylammonium porphyrin and reduced liquid crystalline graphene oxide that can be utilized for the electrocatalytic reduction of CO2to CO on a glassy carbon electrode in aqueous electrolyte. The FePGF results in an outstanding robust catalytic performance for the production of CO with 97.0% faradaic efficiency at an overpotential of 480 mV and superior long-term stability relative to other heterogeneous molecular complexes of over 24 h (cathodic energy efficiency: 58.1%). In addition, a high surface area carbon fiber paper is used as a substrate for FePGF catalyst, resulting in enhanced current density of 1.68 mA cm-2with 98.7% CO faradaic efficiency at an overpotential of 430 mV for 10 h, corresponding to a turnover frequency of 2.9 s-1and 104 400 turnover number. Furthermore, FePGF/CFP has one of the highest cathodic energy efficiencies (60.9%) reported for immobilized metal complex catalysts.