Energy efficient electrochemical reduction of CO2 to CO using a three-dimensional porphyrin/graphene hydrogel

Although electrochemical CO2 reduction is one of the most promising ways to convert atmospheric CO2 into value-added chemicals, there are still numerous limitations to overcome to achieve highly efficient CO2 conversion performance. Herein, we report for the first time the development and use of a three-dimensional iron porphyrin-based graphene hydrogel (FePGH) as an electrocatalyst for extremely efficient robust CO2 reduction to CO. Electrocatalytic CO2 conversion was performed in aqueous medium with FePGH, which has a highly porous and conductive 3D graphene structure, resulting in high catalytic activity for CO production with ∼96.2% faradaic efficiency at a very low overpotential of 280 mV. Furthermore, FePGH showed considerable catalytic durability maintaining a consistent CO yield (96.4% FE) over 20 h electrolysis at the same overpotential, corresponding to the highest cathodic energy efficiency yet observed of 79.7% compared to other state-of-the-art immobilised metal complex electrocatalysts. This approach to fabricating a 3D graphene-based hydrogel electrocatalyst should provide an exciting new avenue for the development of other kinds of molecular electrocatalysts.