Efficient Heterogeneous CO2 to CO Conversion with a Phosphonic Acid Fabricated Cofacial Iron Porphyrin Dimer

For developing renewable fuels and controlling global warming, catalyst promoted conversion of CO2 to CO is essential. Numerous CO2 to CO conversion molecular catalysts have shown very high activity and stability. For large-scale conversion, immobilization of the molecular catalysts to conducting electrodes is essential. Several efficient molecular catalysts have been immobilized to conducting electrodes via physical bonds. We found that immobilization of a monolayer of the highly efficient Fe porphyrin dimer molecular catalyst via a phosphonic acid anchor to a fluorine-doped tin oxide electrode, FTO/Fe2DTPFPP-PO3H2 showed high activity and stability for CO2 to CO conversion at a very low catalyst loading in nonaqueous and aqueous solutions. A high current density was achieved for the CO2 to CO conversion by loading more amount of the catalyst to a thin mesoporous layer of SnO2 or TiO2 nanoparticles on FTO. In neutral aqueous solutions, the noninnocent behavior of the FTO electrode was overcome by modifying its catalyst-free surface with hydrophobic n-butyl phosphonic acid groups.