Two-dimensional (2D) materials are promising for applications in a wide range of fields because of their unique properties. Hydrogen boride sheets, a new 2D material recently predicted from theory, exhibit intriguing electronic and mechanical properties as well as hydrogen storage capacity. Here, we report the experimental realization of 2D hydrogen boride sheets with an empirical formula of HB, produced by exfoliation and complete ion-exchange between protons and magnesium cations in magnesium diboride (MgB) with an average yield of 42.3% at room temperature. The sheets feature an sp-bonded boron planar structure without any long-range order. A hexagonal boron network with bridge hydrogens is suggested as the possible local structure, where the absence of long-range order was ascribed to the presence of three different anisotropic domains originating from the 2-fold symmetry of the hydrogen positions against the 6-fold symmetry of the boron networks, based on X-ray diffraction, X-ray atomic pair distribution functions, electron diffraction, transmission electron microscopy, photo absorption, core-level binding energy data, infrared absorption, electron energy loss spectroscopy, and density functional theory calculations. The established cation-exchange method for metal diboride opens new avenues for the mass production of several types of boron-based 2D materials by countercation selection and functionalization.

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We conducted uniaxial compression and grain growth experiments on fine‐grained (~1 μm) forsterite +20 vol% enstatite aggregates. Based on analyses of the sensitivity of the strain rate as a function of stress, we find power law creep at low stress, Newtonian creep at intermediate stress, and again power law creep at high stress, which correspond to interface‐controlled diffusion creep, grain boundary diffusion (Coble) creep, and a dislocation‐controlled process, respectively. The creep rate of these samples is well expressed by a combination of strain rates of these three mechanisms where interface‐controlled and Coble creep rates are combined as series‐sequential processes, while the rate of the dislocation process is added with them as a parallel‐concurrent process. Mechanical data collected continuously during the application of a constant load but while slowly changing temperature were decomposed into data for every 1 °C, which allowed consideration of >600 mechanical data points from 1054 to 1370 °C. The data were analyzed using Bayesian statistics implementing a Markov chain Monte Carlo method imposed on the above constitutive equation, resulting in the best fit flow law parameters for interface‐controlled and Coble creep. Samples were annealed for 500 hr at various temperatures. A comparison of the final grain sizes as a function of temperature on an Arrhenius plot resulted in an activation energy for grain growth similar to that observed for grain boundary diffusion during Coble creep of these materials.

The reaction between N 2 O and CH 4 over an Fe ion-exchanged BEA zeolite (Fe-BEA) catalyst was studied by using a pulse reaction technique, temperature-programmed desorption (TPD) and infrared (IR) spectroscopy. N 2 O readily reacted with CH 4 in the presence of an N 2 O + CH 4 mixture above 200 C, while both the O 2 + CH 4 reaction and the catalytic decomposition of N 2 O over the Fe-BEA catalyst required higher temperatures (above 400 C). In the O 2 -TPD studies, a desorption peak of O 2 was observed above 600 C after O 2 treatment at 250 C, while a new O 2 desorption peak appeared at the lower temperatures after N 2 O treatment at 250 C. However, the new O(a) species resulting from the N 2 O treatment hardly reacted with CH 4 even at 350 C, which was confirmed by the CH 4 -pulsed experiments. On the other hand, a new IR band at 3683 cm À1 , which can be assigned to the OH group on Fe ion species, was observed after O 2 or N 2 O treatment. The peak intensity at 3683 cm À1 was not changed in the exposure of CH 4 only, but decreased in the exposure of N 2 O + CH 4 mixture above 150 C. At the same time, the CH x O y (a) species such as Fe-OCH 3 were formed, which were observed by IR measurements. The adsorbed surface species showed a high reactivity with N 2 O even at low temperatures ($200 C). A possible mechanism is discussed in terms of active oxygen species such as nascent oxygen transients (O*(a)), which are formed in the exposure of N 2 O + CH 4 mixture, and may play an important role in the activation/oxidation of CH 4 at initial steps to form CH x O y (a) species.

Modification of Pt/SiO 2 with ReO x species enhanced the catalytic activity of the CO oxidation with O 2 in the presence of H 2 . The amount of Re modifier on Pt-ReO x /SiO 2 was optimized to be Re/Pt ) 0.5 on the molar basis. The promoting effect of Re species appeared after the reduction above 673 K. Characterization of the reduced Pt-ReO x /SiO 2 catalyst by means of EXAFS, XANES, temperature-programmed reduction, and CO adsorption measurements suggested the formation of the ReO x clusters on the surface of Pt metal particles with the average valence of Re of +2.7. The CO adsorption on Pt-ReO x /SiO 2 gave a higher wavenumber then that on Pt/SiO 2 at the same CO coverage, showing the weakened interaction between CO and the Pt surface, which is also supported by the desorption profile of the adsorbed CO. The CO coverage on Pt-ReO x / SiO 2 during the preferential CO oxidation was much smaller than that in the absence of H 2 , suggesting that an oxygen-containing species was coadsorbed on the reduced catalyst. The pulse reaction showed that the reduced Pt-ReO x /SiO 2 can activate O 2 even when the catalyst surface is saturated with CO. These tendencies can be explained by the mechanism where the reduced ReO x species activates O 2 and the oxidizing species is spilled over from the ReO x species to the Pt surface.

Addition of potassium enhanced the activity of preferential CO oxidation on Pt/Al 2 O 3. The additive effect of potassium weakened the interaction between CO and Pt, and it also changed the CO adsorption site. FT-IR observation under the PROX condition suggests the presence of adsorbed species derived from O 2 and H 2 such as OH species, which can be related to the promoting effect of H 2 presence in the PROX reaction.

Examinations of CO2 formed during steady-state CO oxidation reactions were performed using infrared (IR) chemiluminescence. The CO2 was formed using a molecular-beam method over Pd(110) and Pd(111). The CO2 formation rate is temperature dependent under various partial pressure conditions. The temperature of the maximum formation rate is denoted as TSmax. Analyses of IR emission spectra at surface temperatures higher than TSmax showed that the average vibrational temperature (TVAV) is higher for Pd(111) than for Pd(110). The antisymmetric vibrational temperature (TVAS) is almost equal on both surfaces. These results suggest that the activated CO2 complex is more bent on Pd(111) and straighter on Pd(110). Furthermore, the difference in the TVAV value was small for surface temperatures less than TSmax. The TVAS value was much higher than TVAV on both surfaces. These phenomena were observed only when the surface temperature was lower than TSmax: they became more pronounced at lower temperatures, suggesting that the activated complex of CO2 formation is much straighter on both Pd surfaces than that observed at higher surface temperatures. Combined with kinetic results, the higher CO coverage at the lower surface temperatures is inferred to be related to the linear activated complex of CO2 formation.

It is found that the addition of Mo to Rh/SiO 2 (Mo-Rh/SiO 2 ) promoted alcohol formation in hydroformylation of propylene and ethylene, at the same time it drastically enhanced the activity of hydroformylation and hydrogenation. It is suggested that H 2 adsorption sites, which are not inhibited by CO adsorption, are present on Mo-Rh/SiO 2 . The sites can cause high H 2 activation, and it can be related to the additive effect of Mo in hydroformylation reactions.