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Rb is Magnesium structured and crystallizes in the orthorhombic Cmcm space group. The structure is three-dimensional. Rb is bonded to twelve equivalent Rb atoms to form a mixture of edge, face, and corner-sharing RbRb12 cuboctahedra. There are a spread of Rb–Rb bond distances ranging from 4.99–5.11 Å.
Rb crystallizes in the orthorhombic Fddd space group. The structure is three-dimensional. Rb is bonded to seven equivalent Rb atoms to form a mixture of distorted edge and corner-sharing RbRb7 pentagonal bipyramids. There are a spread of Rb–Rb bond distances ranging from 4.61–4.98 Å.
Rb is alpha-like structured and crystallizes in the orthorhombic Fddd space group. The structure is three-dimensional. Rb is bonded in a distorted hexagonal planar geometry to six equivalent Rb atoms. There are a spread of Rb–Rb bond distances ranging from 4.58–4.97 Å.
Recent studies have shown that appropriate levels of alkali promotion can significantly improve the rate of low-temperature water gas shift (LT-WGS) on a range of catalysts. At sufficient loadings, the alkali metal can weaken the formate C–H bond and promote formate dehydrogenation, which is the proposed rate determining step in the formate associative mechanism. In a continuation of these studies, the effect of Rb promotion on Pt/ZrO 2 is examined herein. Pt/ZrO 2 catalysts were prepared with several different Rb loadings and characterized using temperature programmed reduction mass spectrometry (TPR-MS), temperature programmed desorption (TPD), diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS), an X-ray absorption near edge spectroscopy (XANES) difference procedure, extended X-ray absorption fine structure spectroscopy (EXAFS) fitting, TPR-EXAFS/XANES, and reactor testing. At loadings of 2.79% Rb or higher, a significant shift was seen in the formate ν(CH) band. The results showed that a Rb loading of 4.65%, significantly improves the rate of formate decomposition in the presence of steam via weakening the formate C–H bond. However, excessive rubidium loading led to the increase in stability of a second intermediate, carbonate and inhibited hydrogen transfer reactions on Pt through surface blocking and accelerated agglomeration during catalyst activation. Optimal catalytic performance was achieved with loadings in the range of 0.55–0.93% Rb, where the catalyst maintained high activity and exhibited higher stability in comparison with the unpromoted catalyst.
Recently, metal halide perovskites have emerged as promising semiconductor candidates for sensitive X-ray photon detection due to their suitable band gap energies, excellent charge transport properties, and low material cost afforded by their low-temperature solution-processing preparation. Furthermore, we report an improved methodology for single crystal growth and thermal and electrical properties of a two-dimensional (2D) layered halide material Rb 4 Ag 2 BiBr 9 , which has been identified as a potential candidate for X-ray radiation detection applications. The measured heat capacity for Rb 4 Ag 2 BiBr 9 implies that there are no structural phase transitions upon cooling. Temperature dependence of thermal transport measurements further suggests remarkably low thermal conductivities of Rb 4 Ag 2 BiBr 9 that are comparable to the lowest reported in literature. The bulk crystal resistivity is determined to be 2.59 × 10 9 Ω·cm from the current–voltage (I–V) curve. Density of trap states is estimated to be ~10 10 cm –3 using the space-charge-limited-current measurements. The fabricated Rb 4 Ag 2 BiBr 9 -based X-ray detector shows good operational stability with no apparent current drift, which may be ascribed to the 2D crystal structure of Rb 4 Ag 2 BiBr 9 . Finally, by varying the X-ray tube current to change the corresponding dose rate, the Rb4Ag2BiBr9 X-ray detector sensitivity is determined to be 222.03 μC Gy –1 cm –2 (at an electric field of E = 24 V/mm).
The flux synthesis of a uranium gallophosphate and a uranium gallate, Cs 4 [UO 2 Ga 2 (PO 4 ) 4 ] and Cs 2 UO 2 Ga 2 O 5 , and 4 uranium phosphates, [Rb 2 Rb 3.93 Cl 0.93 ][(UO 2 ) 5 (PO 4 ) 5 ], Rb 11 [(UO 2 ) 8 (PO 4 ) 9 ], Rb 7.6 [(UO 2 ) 8 O 8.6 F 0.4 (PO 4 ) 2 ], and Rb 6 [(UO 2 ) 5 O 2 (PO 4 ) 4 ], is reported.
The ethanol steam reforming reaction (ESR) was investigated on unpromoted and potassium- and rubidium-promoted monoclinic zirconia-supported platinum (Pt/m-ZrO 2 ) catalysts. Evidence from in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) characterization indicates that ethanol dissociates to ethoxy species, which undergo oxidative dehydrogenation to acetate followed by acetate decomposition. The acetate decomposition pathway depends on catalyst composition. The decarboxylation pathway tends to produce higher overall hydrogen selectivity and is the most favored route at high alkali loading (2.55 wt.% K and higher or 4.25 wt.% Rb and higher). On the other hand, decarbonylation is a significant route for the undoped catalyst or when a low alkali loading (e.g., 0.85% K or 0.93% Rb) is used, thus lowering the overall H 2 selectivity of the process. Results of in situ DRIFTS and the temperature-programmed reaction of ESR show that alkali doping promotes forward acetate decomposition while exposed metallic sites tend to facilitate decarbonylation. In previous work, 1.8 wt.% Na was found to hinder decarbonylation completely. Due to the fact that 1.8 wt.% Na is atomically equivalent to 3.1 wt.% K and 6.7 wt.% Rb, the results show that less K (2.55% K) or Rb (4.25% Rb) is needed to suppress decarbonylation; that is, more basic cations are more efficient promoters for improving the overall hydrogen selectivity of the ESR process.
Rb(BH)6 crystallizes in the cubic Fm-3 space group. The structure is three-dimensional. Rb is bonded in a distorted q6 geometry to twelve equivalent H atoms. All Rb–H bond lengths are 3.00 Å. B is bonded in a single-bond geometry to one H atom. The B–H bond length is 1.20 Å. H is bonded in a single-bond geometry to two equivalent Rb and one B atom.
Rb(TeO3)2 crystallizes in the cubic Fd-3m space group. The structure is three-dimensional. Rb is bonded to six equivalent O atoms to form RbO6 octahedra that share corners with twelve equivalent TeO6 octahedra. The corner-sharing octahedral tilt angles are 68°. All Rb–O bond lengths are 3.21 Å. Te is bonded to six equivalent O atoms to form TeO6 octahedra that share corners with six equivalent RbO6 octahedra and corners with six equivalent TeO6 octahedra. The corner-sharing octahedra tilt angles range from 43–68°. All Te–O bond lengths are 2.00 Å. O is bonded in a 3-coordinate geometry to one Rb and two equivalent Te atoms.
Rb(MoTe)3 crystallizes in the hexagonal P6_3/m space group. The structure is three-dimensional. Rb is bonded in a 9-coordinate geometry to nine equivalent Te atoms. There are three shorter (3.76 Å) and six longer (3.81 Å) Rb–Te bond lengths. Mo is bonded in a 10-coordinate geometry to six equivalent Mo and four equivalent Te atoms. There are two shorter (2.66 Å) and four longer (2.78 Å) Mo–Mo bond lengths. There are a spread of Mo–Te bond distances ranging from 2.83–2.89 Å. Te is bonded in a 7-coordinate geometry to three equivalent Rb and four equivalent Mo atoms.
Rb(MoS)3 crystallizes in the hexagonal P6_3/m space group. The structure is three-dimensional. Rb is bonded in a 9-coordinate geometry to nine equivalent S atoms. There are three shorter (3.57 Å) and six longer (3.61 Å) Rb–S bond lengths. Mo is bonded in a distorted see-saw-like geometry to four equivalent S atoms. There are a spread of Mo–S bond distances ranging from 2.49–2.60 Å. S is bonded in a 7-coordinate geometry to three equivalent Rb and four equivalent Mo atoms.
Rb(RhAs)2 crystallizes in the tetragonal I4/mmm space group. The structure is three-dimensional. Rb is bonded in a body-centered cubic geometry to eight equivalent As atoms. All Rb–As bond lengths are 3.60 Å. Rh is bonded to four equivalent As atoms to form a mixture of edge and corner-sharing RhAs4 tetrahedra. All Rh–As bond lengths are 2.45 Å. As is bonded in a 8-coordinate geometry to four equivalent Rb and four equivalent Rh atoms.
Rb(RhP)2 crystallizes in the tetragonal I4/mmm space group. The structure is three-dimensional. Rb is bonded in a body-centered cubic geometry to eight equivalent P atoms. All Rb–P bond lengths are 3.55 Å. Rh is bonded to four equivalent P atoms to form a mixture of corner and edge-sharing RhP4 tetrahedra. All Rh–P bond lengths are 2.35 Å. P is bonded in a 8-coordinate geometry to four equivalent Rb and four equivalent Rh atoms.
Rb(MoSe)3 crystallizes in the hexagonal P6_3/m space group. The structure is three-dimensional. Rb is bonded in a 9-coordinate geometry to nine equivalent Se atoms. There are three shorter (3.61 Å) and six longer (3.65 Å) Rb–Se bond lengths. Mo is bonded in a distorted see-saw-like geometry to four equivalent Se atoms. There are a spread of Mo–Se bond distances ranging from 2.64–2.72 Å. Se is bonded in a 7-coordinate geometry to three equivalent Rb and four equivalent Mo atoms.
Rb(WO4)8 crystallizes in the monoclinic C2/m space group. The structure is three-dimensional. Rb is bonded in a distorted square co-planar geometry to four equivalent O atoms. All Rb–O bond lengths are 2.95 Å. There are two inequivalent W sites. In the first W site, W is bonded to six O atoms to form corner-sharing WO6 octahedra. The corner-sharing octahedra tilt angles range from 0–16°. There are a spread of W–O bond distances ranging from 1.86–2.00 Å. In the second W site, W is bonded to six O atoms to form distorted corner-sharing WO6 octahedra. The corner-sharing octahedra tilt angles range from 8–19°. There are a spread of W–O bond distances ranging from 1.77–2.14 Å. There are eleven inequivalent O sites. In the first O site, O is bonded in a single-bond geometry to one W atom. In the second O site, O is bonded in a distorted bent 120 degrees geometry to one Rb and one W atom. In the third O site, O is bonded in a distorted water-like geometry to two equivalent O atoms. Both O–O bond lengths are 2.06 Å. In the fourth O site, O is bonded in a linear geometry to two equivalent W atoms. In the fifth O site, O is bonded in a linear geometry to two equivalent W atoms. In the sixth O site, O is bonded in a bent 150 degrees geometry to two equivalent W atoms. In the seventh O site, O is bonded in a linear geometry to two equivalent W atoms. In the eighth O site, O is bonded in a single-bond geometry to one W and one O atom. In the ninth O site, O is bonded in a linear geometry to two equivalent W atoms. In the tenth O site, O is bonded in a linear geometry to two W atoms. In the eleventh O site, O is bonded in a linear geometry to two W atoms.
Rb(PtGe)4 crystallizes in the tetragonal I4 space group. The structure is three-dimensional. Rb is bonded in a 8-coordinate geometry to eight equivalent Pt atoms. There are four shorter (3.42 Å) and four longer (3.56 Å) Rb–Pt bond lengths. Pt is bonded in a 7-coordinate geometry to two equivalent Rb and five equivalent Ge atoms. There are a spread of Pt–Ge bond distances ranging from 2.51–2.63 Å. Ge is bonded in a 5-coordinate geometry to five equivalent Pt atoms.
Rb(IrAs)2 crystallizes in the tetragonal I4/mmm space group. The structure is three-dimensional. Rb is bonded in a body-centered cubic geometry to eight equivalent As atoms. All Rb–As bond lengths are 3.57 Å. Ir is bonded to four equivalent As atoms to form a mixture of distorted edge and corner-sharing IrAs4 tetrahedra. All Ir–As bond lengths are 2.47 Å. As is bonded in a 8-coordinate geometry to four equivalent Rb and four equivalent Ir atoms.
Rb(IrP)2 crystallizes in the tetragonal I4/mmm space group. The structure is three-dimensional. Rb is bonded in a body-centered cubic geometry to eight equivalent P atoms. All Rb–P bond lengths are 3.56 Å. Ir is bonded to four equivalent P atoms to form a mixture of distorted edge and corner-sharing IrP4 tetrahedra. All Ir–P bond lengths are 2.36 Å. P is bonded in a 8-coordinate geometry to four equivalent Rb and four equivalent Ir atoms.