Search

Blue-emitting Cs 3 Cu 2 I 5 has attracted attention owing to its near-unity PL quantum yield and applications in DUV photodetectors and scintillators. Its PL properties originate from the unique local structure around the luminescent center, the [Cu 2 I 5 ] 3- polyhedron iodocuprate anion consisting of the edge-shared CuI 3 triangle and the CuI 4 tetrahedron dimer, which is isolated by Cs + ions. We found that solid-state reactions between CsI and CuI occur near room temperature (RT) to form Cs 3 Cu 2 I 5 and/or CsCu 2 I 3 phases. High-quality thin films of these phases were obtained by the sequential deposition of CuI and CsI by thermal evaporation. We elucidated that the formation of interstitial Cu + and the antisite of I - at the Cs + site in the CsI crystal through Cu + and I - diffusion results in the RT synthesis of Cs 3 Cu 2 I 5 . The unique structure formation of the luminescent center was revealed using a model based on the low packing density of the CsCl-type crystal structure, similar sizes of Cs + and I - ions, and the high diffusivity of Cu + . The self-aligned patterning of the luminous regions on thin films was demonstrated.

Electrides are promising support materials to promote transition metal catalysts for ammonia synthesis due to their strong electron-donating ability. Cobalt (Co) is an alternative non-noble metal catalyst to ruthenium in ammonia synthesis; however, it is difficult to achieve acceptable activity at low temperatures due to the weak Co-N interaction. Here, we report a novel oxyhydride electride, BaAl 2 O 4- x H y , that can significantly promote ammonia synthesis over Co (500 mmol g Co -1 h -1 at 340 °C and 0.90 MPa) with a very low activation energy (49.6 kJ mol -1 ; 260-360 °C), which outperforms the state-of-the-art Co-based catalysts, being comparable to the latest Ru catalyst at 300 °C. BaAl 2 O 4- x H y with a stuffed tridymite structure has interstitial cage sites where anionic electrons are accommodated. The surface of BaAl 2 O 4- x H y with very low work functions (1.7-2.6 eV) can donate electrons strongly to Co, which largely facilitates N 2 reduction into ammonia with the aid of the lattice H - ions. The stuffed tridymite structure of BaAl 2 O 4- x H y with a three-dimensional AlO 4 -based tetrahedral framework has great chemical stability and protects the accommodated electrons and H - ions from oxidation, leading to robustness toward the ambient atmosphere and good reusability, which is a significant advantage over the reported hydride-based catalysts.

CO 2 hydrogenation to methanol is one of the most promising routes to CO 2 utilization. However, difficulty in CO 2 activation at low temperature, catalyst stability, catalyst preparation, and product separation are obstacles to the realization of a practical hydrogenation process under mild conditions. Here, we report a PdMo intermetallic catalyst for low-temperature CO 2 hydrogenation. This catalyst can be synthesized by the facile ammonolysis of an oxide precursor and exhibits excellent stability in air and the reaction atmosphere and significantly enhances the catalytic activity for CO 2 hydrogenation to methanol and CO compared with a Pd catalyst. A turnover frequency of 0.15 h -1 was achieved for methanol synthesis at 0.9 MPa and 25 °C, which is comparable to or higher than that of the state-of-the-art heterogeneous catalysts under higher-pressure conditions (4-5 MPa).

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.