Hexagonal BaTiO (3- x ) H x 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 ( P 6 ₃ / mmc ) was synthesized by the direct reaction of BaH ₂ and TiO ₂ at 800 °C under a stream of hydrogen, and the estimated chemical composition was BaTiO _2.01 H _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.