Facile formation of barium titanium oxyhydride on a titanium hydride surface as an ammonia synthesis catalyst.

Oxyhydrides are promising compounds as supports for ammonia synthesis catalysts because they suppress hydrogen poisoning on the catalyst surface and enhance the ammonia synthesis activity. Herein, we developed a facile method for preparing BaTiO2.5H0.5, a perovskite oxyhydride, on a TiH2 surface via the conventional wet impregnation method using TiH2 and Ba hydroxide. Scanning electron microscopy and high-angle annular dark-field scanning transmission electron microscopy observations revealed that BaTiO2.5H0.5 crystallized as nanoparticles of ca. 100-200 nm on the TiH2 surface. The Ru-loaded catalyst Ru/BaTiO2.5H0.5-TiH2 exhibited 2.46 times higher ammonia synthesis activity (3.05 mmol-NH3 g-1 h-1 at 400 °C) than the benchmark Ru catalyst Ru-Cs/MgO (1.24 mmol-NH3 g-1 h-1 at 400 °C) because of the suppression of hydrogen poisoning. The analysis of reaction orders showed that the effect of suppressing hydrogen poisoning on Ru/BaTiO2.5H0.5-TiH2 was equivalent to that of the reported Ru/BaTiO2.5H0.5 catalyst, thus supporting the formation of BaTiO2.5H0.5 perovskite oxyhydride. This study demonstrated that the selection of appropriate raw materials facilitates the formation of BaTiO2.5H0.5 oxyhydride nanoparticles on the TiH2 surface using the conventional synthesis method.

Enhanced ammonia synthesis activity of Ru-supported cerium-lanthanum oxide induced by Ti substitution forming mesopores.

Ru/Ce0.5La0.5-xTixO1.75+0.5x solid solutions with cubic fluorite structure were successfully synthesized via the polymerized complex method. While the Ti substitution enhanced Ce4+ reducibility by compensating for oxygen vacancies, the reducibility showed no correlation with ammonia synthesis activity. However, Ru/Ce0.5La0.4Ti0.1O1.8 showed the highest activity originating from the facilitated formation of mesopores.

Rational synthesis of supramolecular assemblies based on tetraplatinum units: synthesis, characterization, and selective substitution reactions of four different Pt4 clusters.

Four different types of square-planar Pt(4) clusters, trans-[Pt(4)(µ-OCOCH(3))(6)(µ-ArNCHNAr)(2)] (2: ArNCHNAr = N,N'-diarylformamidinate), [Pt(4)(µ-OCOCH(3))(7)(µ-ArNCHNAr)] (8), cis-[Pt(4)(µ-OCOCH(3))(6)(κ(4)-N(4)-DArBp)] (9: DArBp = 1,3-bis(arylbenzamidinate)propane), and [Pt(4)Cl(2)(µ-OCOCH(3))(5)(κ(4)-N(2),P(2)-dpfam)] (13: dpfam = N,N'-bis[(2-diphenylphosphino)phenyl]formamidinate), were successfully prepared by using selective substitution reactions of in-plane acetate ligands of [Pt(4)(µ-OCOCH(3))(8)] (1), which has four in-plane and four out-plane acetate ligands, with appropriate capping ligands. Fundamental substitution reactions of the remaining in-plane acetates with benzoic acid derivatives were also investigated. All newly prepared complexes were characterized from spectral and physical data and combustion analysis. X-ray crystallographic studies of some of the clusters were also performed. Electrochemical measurements of amidinate-modified Pt(4) clusters revealed stepwise oxidation processes of the Pt(4) core due to Pt(4)(9+)/Pt(4)(8+) and Pt(4)(10+)/Pt(4)(9+). Based on the lability of the in-plane acetate ligands of the modified Pt(4) clusters, reactions of cis-[Pt(4)(µ-OCOCH(3))(6)(κ(4)-N(4)-DArBp)] (9 c: Ar = C(6)H(4)tBu-4) with ferrocenedicarboxylic acid and p-phenylenedipropionic acid resulted in the selective formation of cyclic dimers 17 and 18 and the reaction of 13 with 4,4'-biphenyldicarboxylic acid afforded a linear dimer 20. The dimers were characterized by spectral data, as well as X-ray analyses for 17 and 18. The finding of two Fe(3+)/Fe(2+) redox couples in the electrochemical measurement of dimer 17 indicated that two ferrocenyl units in dimer 17 communicated electronically.

Attenuated Total Reflection Surface-Enhanced Infrared Absorption (ATR SEIRA) Spectroscopy for the Analysis of Fatty Acids on Silver Nanoparticles.

The application of attenuated total reflection surface-enhanced infrared absorption spectroscopy (ATR SEIRA) to the analysis of fatty acids on silver nanoparticles was investigated. Attenuated total reflection measurements using four types of internal reflection elements (IREs)-zinc selenide, diamond, silicon, and germanium-were performed for silver nanoparticles modified with fatty acids, and germanium IRE was shown to be suitable for the analysis of silver nanoparticles, even when the sample had a high refractive index. Fatty acids coating the silver nanoparticles could be directly identified by SEIRA enhancement, because both symmetric carboxylate stretching vibration and methylene wagging vibration were strongly detected. Furthermore, the peak positions for methylene wagging vibration differed depending on the carbon number of the fatty acid, so that information from the ATR SEIRA spectra makes it possible to identify substances coating silver nanoparticles. Therefore, ATR SEIRA would appear to have significant potential as a technique for the identification of substances coated on metal nanoparticle surfaces.