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A layered double hydroxide (LDH) composed of Ni 2+ and Fe 3+ with a Fe 3+ /(Ni 2+ + Fe 3+ ) ratio of 0.05, which is not commonly available, was successfully prepared by coprecipitation from an aqueous solution of glycerol containing nickel nitrate and iron nitrate. Precipitation using NaOH as a precipitating agent at room temperature or 120 °C under hydrothermal conditions gave products with micrometer-sized aggregates of nanometer-sized unshaped particles, while that using urea yielded LDHs with a foam-like porous architecture composed of platy particles with a size of 100-300 nm. The products were examined to remove Cr(VI) from an acidic (pH = 3) aqueous solution of K 2 Cr 2 O 7 by adsorption and photocatalytic reduction. The foam-like porous NiFe-LDH exhibited the highest adsorbed amount (122 mg g -1 ) and rate (0.017 g mg -1 min -1 ) in the dark and the highest rate (0.012 min -1 ) of photocatalytic Cr(VI) reduction among the NiFe-LDHs prepared in the present study, which can be explained as a positive effect of the foam-like porous architecture. These performances were superior to those of other reported LDHs, showing the importance of the composition and the particle morphology to boost the removal of Cr(VI).

Bismuth oxyhalides and layered alkali titanates are promising components to design high-performance hybrid photocatalysts. In this work, a hybrid photocatalyst composed of lepidocrocite-type layered cesium titanate (Cs 0.7 Ti 1.77 Li 0.23 O 4 , CsTLO) and bismuth oxyiodide (BiOI) was designed rationally based on lattice matching. BiOI formed on the layered titanate by ion exchange of CsTLO with Bi cations and subsequent growth of BiOI nanodisks (6 nm in the thickness and 125 nm in the lateral size) in an aqueous solution of cesium iodide, resulting in the hybrid where BiOI nanodisks were lying flat on the layered titanate and exposed the (001) facet predominantly. The present hybrid exhibited efficient photodegradation of methylene blue (4, 10, and 14 times higher than that of CsTLO, Bi-TLO, and BiOI, respectively), which was ascribed to the efficient charge transfer in the bulk and at the interface assisted by the built-in internal electric fields and the high activity of (001) BiOI for direct oxidation of the pollutant.