Influence of the presence of RuO2 on the reactivity of Fe2O3 in the Artificial Photosynthesis reaction.

Abstract

Surface Plasmonic Resonance (SPR) is the oscillation of free electrons on the surface of a metal or metallic particle upon irradiation with light of a certain frequency. The incorporation of Fe2O3 (a H2O oxidising photocatalyst) with plasmonic RuO2 nanoparticles to form a composite is studied. XRD results show that RuO2 is formed in the rutile phase while Fe2O3 is rhombohedral and also suggests doping of the Fe2O3 lattice with Ru atoms in the composite. UV-Vis spectroscopy shows that RuO2 exhibits a plasmon peak at 511nm, and CO2-TPD experiments show that RuO2 adsorbs and desorbs CO2. TEM also shows that the RuO2 particles are spherical, as are the Fe2O3 particles with some irregular polyhedra present, too. The composite is a mixture of these two morphologies.The effect of composite formation on the activity of the materials in the artificial photosynthesis reaction is dramatic. Neither RuO2 nor Fe2O3 alone produce significant quantities of gaseous CH4 or CO products. However, the composite material produces both (as well as generating levels of unidentified adsorbed hydrocarbonaceous species).This reactivity is ascribed to the generation of a heterojunction in the composite material. It is suggested that the generation of holes in Fe2O3 is used to provide protons (from H2O oxidation), and the decay of an SPR response on RuO2 provides hot electrons, which together with the protons reduce CO2 to produce CH4, CO and adsorbed hydrocarbonaceous species.