RuO2/TiO2 photocatalysts prepared via a hydrothermal route: Influence of the presence of TiO2 on the reactivity of RuO2 in the artificial photosynthesis reaction

The incorporation of TiO2 (at two different loadings) with plasmonic RuO2 nanoparticles (with an average size of (3 ± 0.7) nm) to form nanocomposites is studied. XRD results show that RuO2 is formed in the rutile phase, while high levels of TiO2 forms the rutile phase and lower levels form the anatase phase. XRD also confirms doping of TiO2 with Ru atoms and vice versa (doping of RuO2 with Ti atoms) in the nanocomposites. The effect of TiO2 incorporation on the reactivity of RuO2 in the artificial photosynthesis reaction under visible light (which TiO2 cannot absorb) is dramatic. The activities of the catalysts (once TiO2 is included in the composite) significantly increase, and the selectivity of the reactions change with the formation of CH4 and adsorbed hydrocarbonaceous species found alongside the CO + O2 formed over pure RuO2 catalysts. This is ascribed to the generation of a heterojunction interface in the composite material. Following the absorption of visible light, hot electrons (derived from the RuO2 plasmon) become sufficiently energetic to be transferred to the TiO2 CB. From this level the electrons can generate nascent hydrogen which subsequently reacts with (and reduces) adsorbed CO2 molecules.