Hexagonal BaTiO_(3-H Oxyhydride as a Water-Durable Catalyst Support for Chemoselective Hydrogenation

We present heavily H^--doped BaTiO_(3-H (x ≈ 1) as an efficient and water-durable catalyst support for Pd nanoparticles applicable to liquid-phase hydrogenation reactions. The BaTiO_(3-H 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-H as a catalyst support was examined for the selective hydrogenation of unsaturated C-C bonds by Pd nanoparticles deposited on BaTiO_(3-H. We found that the turnover frequency for phenylacetylene hydrogenation per total amount of Pd in Pd/BaTiO_(3-H 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-H 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.