Single-Site, Heterogeneous Electrocatalytic Reduction of CO2 in Water as the Solvent

Abstract

Creating stable surface-bound molecular catalysts for CO2 reduction in aqueous solutions for either electrochemical or photoelectrochemical reduction is a continuing challenge. We report here the preparation and characterization of thin oxide/carbon nanotube electrodes on fluorine-doped tin oxide (FTO) electrodes. The electrodes were prepared by atomic layer deposition (ALD) of ∼15 nm of TiO2 followed by a layer of carbon nanotubes and a thin (2 nm) overlayer of TiO2 for surface stabilization and binding. The phosphonate-derivatized version of the known aqueous solution catalyst for H2/CO reduction, [RuII(tpy-Ph–CH2–PO3H2)(Mebim-py)(H2O)](PF6)2 (tpy-Ph–CH2–PO3H2 = (4-([2, 2′:6′,2″-terpyridin]-4′-yl)benzyl)phosphonic acid; Mebim-py = 3-methyl-1-pyridyl-benzimidazol-2-ylidene), was added to the surface and stabilized by addition of a thin overlayer of TiO2 by ALD. In the derivatized electrodes, the catalyst maintains its reactivity toward CO2 reduction in the short-term, giving mixtures of H2/CO that vary f...