Fabrication of Pd/Mg2 P2 O7 via a Struvite-Template Way from Wastewater and Application as Chemoselective Catalyst in Hydrogenation of Nitroarenes

Raman spectroscopic and X-ray diffraction study of α- and β-Mg2P2O7 at various temperatures

Raman spectra and X-ray diffraction patterns of Mg₂P₂O₇ polymorphs (α- and β-phase) were investigated at various temperatures up to 1073 K at ambient pressure. Typical Raman spectra and X-ray diffraction patterns were observed for the reversible phase transition between low-temperature α-Mg₂P₂O₇ and high- temperature β-Mg₂P₂O₇ during heating and cooling. The effect of temperature on the Raman vibrations for the two Mg₂P₂O₇ polymorphs was quantitatively analyzed. All the observed Raman active bands of the two Mg₂P₂O₇ polymorphs showed linear temperature dependence with different slopes. The quantitative temperature dependences of the Raman bands are -4.01 × 10^-2 ∼ 1.94 × 10^-2 and -2.31 × 10^-2 ∼ -0.44 × 10^-2 cm^-1 K^-1 for α- and β-Mg₂P₂O₇, respectively. The force constant evolution of [P₂O₇]^4- stretching vibrations and the temperature derivatives for both α- and β-Mg₂P₂O₇ were also determined. The thermal expansion coefficient of β-Mg₂P₂O₇ was estimated at 2.97(8) × 10^-5 K^-1. Hence the isobaric mode Grüneisen parameters of β-Mg₂P₂O₇ were calculated.

Hexagonal BaTiO(3-x)Hx Oxyhydride as a Water-Durable Catalyst Support for Chemoselective Hydrogenation

We present heavily H^--doped BaTiO_(3-x)H_x (x ≈ 1) as an efficient and water-durable catalyst support for Pd nanoparticles applicable to liquid-phase hydrogenation reactions. The BaTiO_(3-x)H_x oxyhydride with a hexagonal crystal structure (P6₃/mmc) was synthesized by the direct reaction of BaH₂ and TiO₂ at 800 °C under a stream of hydrogen, and the estimated chemical composition was BaTiO_2.01H_0.96. Density functional theory calculations and magnetic measurements indicated that such heavy H^- doping results in a metallic nature with delocalized electrons and a low work function. The potential of BaTiO_(3-x)H_x as a catalyst support was examined for the selective hydrogenation of unsaturated C-C bonds by Pd nanoparticles deposited on BaTiO_(3-x)H_x. We found that the turnover frequency for phenylacetylene hydrogenation per total amount of Pd in Pd/BaTiO_(3-x)H_x was the highest among the supported Pd catalysts reported to date. The strong electronic charge transfer between Pd and the support, as confirmed by X-ray photoelectron spectroscopy measurements, can be attributed to be responsible for such high catalytic activity. The combination of the BaTiO_(3-x)H_x support and Pd nanoparticles provides for the selective hydrogenation of unsaturated C-C bonds and highlights the validity of catalyst design that integrates H^- in support materials.