Influence of the presence of RuO2 on the reactivity of Fe2O3 in the artificial photosynthesis reaction

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 Fe 2 O 3 (a H 2 O oxidising photocatalyst) with plasmonic RuO 2 nanoparticles to form a composite is studied. XRD results show that RuO 2 is formed in the rutile phase while Fe 2 O 3 is rhombohedral and also suggests doping of the Fe 2 O 3 lattice with Ru atoms in the composite. UV-Vis spectroscopy shows that RuO 2 exhibits a plasmon peak at 511 nm, and CO 2 -TPD experiments show that RuO 2 adsorbs and desorbs CO 2 . TEM also shows that the RuO 2 particles are spherical, as are the Fe 2 O 3 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 RuO 2 nor Fe 2 O 3 alone produce significant quantities of gaseous CH 4 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 Fe 2 O 3 is used to provide protons (from H 2 O oxidation), and the decay of an SPR response on RuO 2 provides hot electrons, which together with the protons reduce CO 2 to produce CH 4 , CO and adsorbed hydrocarbonaceous species.