Mesoporous iron oxide-layered titanate nanohybrids: Soft-chemical synthesis, characterization, and photocatalyst application

Mesoporous iron oxide-layered titanate nanohybrids have been synthesized through a reassembling reaction between exfoliated titanate nanosheets and iron hydroxide nanoclusters, in which an electrostatic attraction between both nanosized species could be achieved at low pH of 1.5. The formation of the layer-by-layer ordered heterostructure with the repeating unit of 1.33 nm was clearly evidenced by powder X-ray diffraction and transmission electron microscopic analysis. According to Fe K-edge X-ray absorption spectroscopy, the hybridized iron oxide crystallizes with loosely packed network of three edge-shared FeO₆ octahedra units. N₂ adsorption-desorption isotherm and diffuse reflectance UV-vis measurements clearly demonstrated that the present iron oxide-layered titanate nanohybrids showed greatly expanded surface areas with mesopores (∼190-230 m²g^-1) and narrow bandgap energies (∼2.3 eV), which are of crucial importance in creating a visible light-active photocatalyst. The test of photocatalytic activity revealed that the present nanohybrids could induce the photodegradation of organic pollutant molecules under visible light illumination (λ > 420 nm). Of special interest is that the chemical stability of iron oxide became remarkably improved upon the hybridization, which could be understood as a result of the encapsulation with titanate layers. In this regard, we could conclude that the present hybridization route is very effective in synthesizing novel visible light-active photocatalysts as well as in stabilizing chemically labile species like iron oxides.