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 CO 2 to CO is essential. Numerous CO 2 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 /Fe 2 DTPFPP-PO 3 H 2 showed high activity and stability for CO 2 to CO conversion at a very low catalyst loading in nonaqueous and aqueous solutions. A high current density was achieved for the CO 2 to CO conversion by loading more amount of the catalyst to a thin mesoporous layer of SnO 2 or TiO 2 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.