Giant Magnetic In-Plane Anisotropy and Competing Instabilities in Na 3 Co 2 SbO 6
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75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
SEARCH · Engineering Papers
Results for “V(CO)6”
Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.
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In-planta production of the biodegradable polyester precursor 2-pyrone-4,6-dicarboxylic acid (PDC): Stacking reduced biomass recalcitrance with value-added co-product
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2-Pyrone-4,6-dicarboxylic acid (PDC)↗
Structural basis for stabilization of Z-DNA by cobalt hexaammine and magnesium cations
In the equilibrium between B-DNA and Z-DNA in poly(dC-dG), the [Co(NH3)6]3+ ion stabilizes the Z form 4 orders of magnitude more effectively than the Mg2+ ion. The structural basis of this difference is revealed in Z-DNA crystal structures of d(CpGpCpGpCpG) stabilized by either Na+/Mg2+ or Na+/Mg2+ plus [Co(NH3)6]3+. The crystals diffract X-rays to high resolution, and the structures were refined at 1.25 A. The [Co(NH3)6]3+ ion forms five hydrogen bonds onto the surface of Z-DNA, bonding to a guanine O6 and N7 as well as to a phosphate group in the ZII conformation. The Mg2+ ion binds through its hydration shell with up to three hydrogen bonds to guanine N7 and O6. Higher charge, specific fitting of more hydrogen bonds, and a more stable complex all contribute to the great effectiveness of [Co(NH3)6]3+ in stabilizing Z-DNA.
NASA Discipline Exobiology↗
Materials Data on Li4V3CoCu2(PO4)6 by Materials Project
Li4V3CoCu2(PO4)6 crystallizes in the triclinic P1 space group. The structure is three-dimensional. there are four inequivalent Li1+ sites. In the first Li1+ site, Li1+ is bonded in a 6-coordinate geometry to six O2- atoms. There are a spread of Li–O bond distances ranging from 2.10–2.51 Å. In the second Li1+ site, Li1+ is bonded in a 6-coordinate geometry to six O2- atoms. There are a spread of Li–O bond distances ranging from 2.06–2.71 Å. In the third Li1+ site, Li1+ is bonded in a 6-coordinate geometry to six O2- atoms. There are a spread of Li–O bond distances ranging from 2.08–2.72 Å. In the fourth Li1+ site, Li1+ is bonded in a 6-coordinate geometry to six O2- atoms. There are a spread of Li–O bond distances ranging from 2.06–2.78 Å. There are three inequivalent V+3.33+ sites. In the first V+3.33+ site, V+3.33+ is bonded to six O2- atoms to form VO6 octahedra that share corners with six PO4 tetrahedra. There are a spread of V–O bond distances ranging from 1.95–2.05 Å. In the second V+3.33+ site, V+3.33+ is bonded to six O2- atoms to form VO6 octahedra that share corners with six PO4 tetrahedra and a faceface with one CuO6 octahedra. There are a spread of V–O bond distances ranging from 1.97–2.06 Å. In the third V+3.33+ site, V+3.33+ is bonded to six O2- atoms to form VO6 octahedra that share corners with six PO4 tetrahedra. There are a spread of V–O bond distances ranging from 1.97–2.12 Å. Co2+ is bonded to six O2- atoms to form distorted CoO6 octahedra that share corners with six PO4 tetrahedra and a faceface with one CuO6 octahedra. There are a spread of Co–O bond distances ranging from 2.01–2.19 Å. There are two inequivalent Cu1+ sites. In the first Cu1+ site, Cu1+ is bonded to six O2- atoms to form distorted CuO6 octahedra that share corners with six PO4 tetrahedra, a faceface with one VO6 octahedra, and a faceface with one CoO6 octahedra. There are a spread of Cu–O bond distances ranging from 2.17–2.38 Å. In the second Cu1+ site, Cu1+ is bonded in a 6-coordinate geometry to six O2- atoms. There are a spread of Cu–O bond distances ranging from 2.14–2.44 Å. There are six inequivalent P5+ sites. In the first P5+ site, P5+ is bonded to four O2- atoms to form PO4 tetrahedra that share a cornercorner with one CoO6 octahedra, a cornercorner with one CuO6 octahedra, and corners with three VO6 octahedra. The corner-sharing octahedra tilt angles range from 26–45°. There are a spread of P–O bond distances ranging from 1.54–1.57 Å. In the second P5+ site, P5+ is bonded to four O2- atoms to form PO4 tetrahedra that share a cornercorner with one CoO6 octahedra, a cornercorner with one CuO6 octahedra, and corners with three VO6 octahedra. The corner-sharing octahedra tilt angles range from 27–45°. There are a spread of P–O bond distances ranging from 1.53–1.57 Å. In the third P5+ site, P5+ is bonded to four O2- atoms to form PO4 tetrahedra that share a cornercorner with one CoO6 octahedra, a cornercorner with one CuO6 octahedra, and corners with three VO6 octahedra. The corner-sharing octahedra tilt angles range from 27–48°. There are a spread of P–O bond distances ranging from 1.53–1.57 Å. In the fourth P5+ site, P5+ is bonded to four O2- atoms to form PO4 tetrahedra that share a cornercorner with one CoO6 octahedra, a cornercorner with one CuO6 octahedra, and corners with three VO6 octahedra. The corner-sharing octahedra tilt angles range from 26–49°. There are a spread of P–O bond distances ranging from 1.52–1.58 Å. In the fifth P5+ site, P5+ is bonded to four O2- atoms to form PO4 tetrahedra that share a cornercorner with one CoO6 octahedra, a cornercorner with one CuO6 octahedra, and corners with three VO6 octahedra. The corner-sharing octahedra tilt angles range from 18–45°. There are a spread of P–O bond distances ranging from 1.52–1.59 Å. In the sixth P5+ site, P5+ is bonded to four O2- atoms to form PO4 tetrahedra that share a cornercorner with one CoO6 octahedra, a cornercorner with one CuO6 octahedra, and corners with three VO6 octahedra. The corner-sharing octahedra tilt angles range from 17–48°. There are a spread of P–O bond distances ranging from 1.51–1.58 Å. There are twenty-four inequivalent O2- sites. In the first O2- site, O2- is bonded in a 2-coordinate geometry to one Li1+, one V+3.33+, and one P5+ atom. In the second O2- site, O2- is bonded in a distorted bent 150 degrees geometry to one Li1+, one V+3.33+, and one P5+ atom. In the third O2- site, O2- is bonded in a 2-coordinate geometry to one Li1+, one V+3.33+, and one P5+ atom. In the fourth O2- site, O2- is bonded in a 4-coordinate geometry to one Li1+, one V+3.33+, one Cu1+, and one P5+ atom. In the fifth O2- site, O2- is bonded in a 3-coordinate geometry to one Li1+, one Co2+, and one P5+ atom. In the sixth O2- site, O2- is bonded in a 3-coordinate geometry to one V+3.33+, one Cu1+, and one P5+ atom. In the seventh O2- site, O2- is bonded in a 3-coordinate geometry to one V+3.33+, one Cu1+, and one P5+ atom. In the eighth O2- site, O2- is bonded in a 4-coordinate geometry to one Li1+, one V+3.33+, one Cu1+, and one P5+ atom. In the ninth O2- site, O2- is bonded in a bent 150 degrees geometry to one V+3.33+ and one P5+ atom. In the tenth O2- site, O2- is bonded in a distorted rectangular see-saw-like geometry to one Li1+, one V+3.33+, one Cu1+, and one P5+ atom. In the eleventh O2- site, O2- is bonded in a 5-coordinate geometry to two Li1+, one Co2+, one Cu1+, and one P5+ atom. In the twelfth O2- site, O2- is bonded in a distorted bent 150 degrees geometry to one V+3.33+ and one P5+ atom. In the thirteenth O2- site, O2- is bonded in a 3-coordinate geometry to one Li1+, one Co2+, and one P5+ atom. In the fourteenth O2- site, O2- is bonded in a distorted rectangular see-saw-like geometry to one Li1+, one V+3.33+, one Cu1+, and one P5+ atom. In the fifteenth O2- site, O2- is bonded in a 5-coordinate geometry to two Li1+, one V+3.33+, one Cu1+, and one P5+ atom. In the sixteenth O2- site, O2- is bonded in a 3-coordinate geometry to one Li1+, one Co2+, and one P5+ atom. In the seventeenth O2- site, O2- is bonded in a 5-coordinate geometry to two Li1+, one V+3.33+, one Cu1+, and one P5+ atom. In the eighteenth O2- site, O2- is bonded in a 5-coordinate geometry to two Li1+, one Co2+, one Cu1+, and one P5+ atom. In the nineteenth O2- site, O2- is bonded in a 5-coordinate geometry to two Li1+, one V+3.33+, one Cu1+, and one P5+ atom. In the twentieth O2- site, O2- is bonded in a 3-coordinate geometry to one Li1+, one V+3.33+, and one P5+ atom. In the twenty-first O2- site, O2- is bonded in a 5-coordinate geometry to two Li1+, one Co2+, one Cu1+, and one P5+ atom. In the twenty-second O2- site, O2- is bonded in a distorted linear geometry to one V+3.33+ and one P5+ atom. In the twenty-third O2- site, O2- is bonded in a bent 150 degrees geometry to one V+3.33+ and one P5+ atom. In the twenty-fourth O2- site, O2- is bonded in a 3-coordinate geometry to one Li1+, one V+3.33+, and one P5+ atom.
36 MATERIALS SCIENCE↗
Temperature-Dependent Mechanical Properties of Ni-Based Concentrated Alloys: Insights from First-Principles Calculations
The present work focuses on predicting temperature-dependent mechanical properties of Ni-based concentrated alloys Ni 18 Cr 10 Co 10 Fe 6 M 4 (abbreviated by X 44 M 4 , with M = Al, V, Mn, Fe, Nb, Mo, and W) using density functional theory (DFT). These predictions are based on shear (plastic) and elastic deformations, utilizing the special quasirandom structure (SQS), the phonon-based quasiharmonic approach (QHA), and the quasistatic approach. The resulting properties include coefficient of thermal expansion via QHA, ideal shear strength (τ IS ), and stable and unstable stacking fault energies (γ SF and γ US ) through pure alias shear deformation, and elastic constants (c ij ), bulk modulus (B 0 ), and shear modules (G 0 ) via elastic deformation. Notably, predicting accurate γ SF is challenging due to uncertainties that can exceed the γ SF values. τ IS and γ US exhibit a strong linear relationship, enabling the accurate prediction of γ US based on the precisely determined τ IS . All mechanical properties of X 44 M 4 decrease with increasing temperature, except for some γ SF cases such as X 44 M 4 with M = V, Mn, Fe, Mo, and W. Among the X 44 M 4 alloys, X 44 Nb 4 exhibits the lowest τ IS , γ US , and G 0 values, and the highest B 0 /G 0 ratio, while X 44 Mn 4 has the lowest B 0 and B 0 /G 0 ratio. We found that volume is a crucial descriptor for understanding and modeling mechanical properties (except B0 and maybe also γ SF ) affected by alloying elements and temperature. Ni-based dilute alloys (e.g., Ni 11 M 1 and Ni 31 M 1 ) and concentrated alloys (e.g., X 44 M 4 ) show similar trends in mechanical properties influenced by alloying elements and temperature, simplifying the analysis and design of Ni-based alloys.
Elastic properties↗
Improving the performance for direct electrolysis of CO 2 in solid oxide electrolysis cells with a Sr 1.9 Fe 1.5 Mo 0.5 O 6– δ electrode via infiltration of Pr 6 O 11 nanoparticles
Direct CO 2 electrolysis using solid oxide electrolysis cells (CO 2 -SOECs) holds promise to efficiently convert carbon dioxide to carbon monoxide and oxygen. Cathodes with desirable catalytic activity and chemical stability play a critical role in the development of direct CO 2 -SOECs. Although Sr 2 Fe 1.5 Mo 0.5 O 6–δ (SFM) has exhibited promise for direct CO 2 -SOECs due to its redox stability, it suffers from insufficient activity for the CO 2 reduction reaction (CO 2 RR). Here we report interface engineering of nanosized Pr 6 O 11 on the SFM cathode obtained through infiltration to promote the CO 2 RR performance for direct CO 2 -SOECs. The effect of Pr 6 O 11 loading on the performance of the CO 2 RR is systematically investigated. At 800 °C, the current density of the Pr 6 O 11 infiltrated SFM cathode with an optimum Pr 6 O 11 loading of 14.8 wt% reaches 1.61 A cm –2 at 1.5 V, more than double that of the SFM cathode (0.76 A cm –2 ) under the same operating conditions. X-ray photoelectron spectroscopy (XPS) characterization and in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) analysis indicate that the adsorption ability of CO 2 on the SFM cathode has been significantly improved by the formation of Pr 6 O 11 . Temperature-programmed desorption (TPD) of CO 2 measurements further manifest that a 14.8 wt% Pr 6 O 11 -SFM cathode has better CO desorption capacity. In addition, polarization resistance of the SFM cathode has significantly decreased with the addition of Pr 6 O 11 . Three-electrode measurement was used to analyze the improved electrode kinetics. Finally, these results demonstrate that the formation of Pr 6 O 11 in the SFM cathode through infiltration is a promising approach for increasing CO 2 RR activity for CO 2 -SOECs.
03 NATURAL GAS↗
Stomatal conductance, not biochemistry, drives low temperature acclimation of photosynthesis in Populus balsamifera , regardless of nitrogen availability
Low temperature thermal acclimation may require adjustments to nitrogen and water use to sustain photosynthesis due to slow enzyme functioning and high-water viscosity. However, understanding of photosynthetic acclimation to temperatures below 11°C is limited. Here, we acclimated Populus balsamifera to 6 °C and 10 °C (6A and 10A, respectively) and provided the trees with either high or low N fertilizer. We measured net CO 2 assimilation rates (A net ), stomatal conductance (g s ), maximum rates of Rubisco carboxylation (V cmax ) and electron transport (J max ), and dark respiration (R d ) at leaf temperatures of 2, 6, 10, 14 and 18 °C, along with leaf N concentrations. The 10A trees had higher A net than the 6A trees at warmer leaf temperatures, which was correlated with higher g s in the 10A trees. The instantaneous temperature responses of V cmax , J max and R d were similar for trees from both acclimation temperatures. While soil N availability increased leaf N concentrations, this had no effect on acclimation of photosynthesis or respiration. Our results indicate that acclimation below 11°C occurred primarily through changes in stomatal conductance, not photosynthetic biochemistry, and was unaffected by short-term N supply. Thermal acclimation of stomatal conductance should therefore be a priority for future carbon cycle model development.
54 ENVIRONMENTAL SCIENCES↗
Fabrication of Large-Area Metal-on-Carbon Catalytic Condensers for Programmable Catalysis
Catalytic condensers stabilize charge on either side of a high-k dielectric film to modulate the electronic states of a catalytic layer for the electronic control of surface reactions. Here, carbon sputtering provided for fast, large-scale fabrication of metal–carbon catalytic condensers required for industrial application. Carbon films were sputtered on HfO 2 dielectric/p-type Si with different thicknesses (1, 3, 6, and 10 nm), and the enhancement of conductance and capacitance of carbon films was observed upon increasing the carbon thickness following thermal treatment at 400 °C. After Pt deposition on the carbon films, the Pt catalytic condenser exhibited a high capacitance of ∼210 nF/cm 2 that was maintained at a frequency ∼1000 Hz, satisfying the requirement for a dynamic catalyst to implement catalytic resonance. Temperature-programmed desorption of carbon monoxide yielded CO desorption peaks that shifted in temperature with the varying potential applied to the condenser (−6 or +6 V), indicating a shift in the binding energy of carbon monoxide on the Pt condenser surface. A substantial increase in capacitance (∼2000 nF/cm 2 ) of the Pt-on-carbon devices was observed at elevated temperatures of 400 °C that can modulate ∼10% of charge per metal atom when 10 V potential was applied. A large catalytic condenser of 42 cm 2 area Pt/C/HfO 2 /Si exhibited a high capacitance of 9393 nF with a low leakage current/capacitive current ratio (<0.1), demonstrating the practicality and versatility of the facile, large-scale fabrication method for metal–carbon catalytic condensers.
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
Crystal structure of butenafine hydrochloride, C 23 H 28 NCl
The crystal structure of butenafine hydrochloride has been solved and refined using synchrotron X-ray powder diffraction data, and optimized using density functional theory techniques. Butenafine hydrochloride crystallizes in space group P2 1 (#4) with a = 13.94807(5), b = 9.10722(2), c = 16.46676(6) Å, β = 93.9663(5)°, V = 2086.733(8) Å 3 , and Z = 4. Butenafine hydrochloride occurs as a racemic co-crystal of R and S enantiomers of the cation. The crystal structure is characterized by parallel stacks of aromatic rings along the b-axis. Each cation forms a strong discrete N–H∙∙∙Cl hydrogen bond. The chloride anions also act as acceptors in several C–H∙∙∙Cl hydrogen bonds from methylene, methyl, and aromatic groups. The powder pattern has been submitted to ICDD for inclusion in the Powder Diffraction File™ (PDF®).
36 MATERIALS SCIENCE↗
CO[subscript 2]-Assisted Oxidative Dehydrogenation of Propane over VO[subscript x]/In[subscript 2]O[
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Jiang, Xiao↗
Materials Data on V5S4 by Materials Project
V5S4 is Titanium telluride structured and crystallizes in the tetragonal I4/m space group. The structure is three-dimensional. there are two inequivalent V sites. In the first V site, V is bonded to five equivalent S atoms to form a mixture of distorted corner and edge-sharing VS5 square pyramids. There are a spread of V–S bond distances ranging from 2.33–2.41 Å. In the second V site, V is bonded in a distorted square co-planar geometry to four equivalent S atoms. All V–S bond lengths are 2.51 Å. S is bonded in a 6-coordinate geometry to six V atoms.
36 MATERIALS SCIENCE↗
Materials Data on Na4V10Co(H11O13)4 by Materials Project
Na4V10Co(H5O6)8(H2O)2O2 crystallizes in the triclinic P-1 space group. The structure is three-dimensional and consists of two water molecules, two water molecules, and one Na4V10Co(H5O6)8 framework. In the Na4V10Co(H5O6)8 framework, there are three inequivalent Na sites. In the first Na site, Na is bonded to six O atoms to form distorted edge-sharing NaO6 octahedra. There are a spread of Na–O bond distances ranging from 2.34–2.72 Å. In the second Na site, Na is bonded to six O atoms to form edge-sharing NaO6 octahedra. There are a spread of Na–O bond distances ranging from 2.43–2.46 Å. In the third Na site, Na is bonded to six O atoms to form edge-sharing NaO6 octahedra. There are a spread of Na–O bond distances ranging from 2.35–2.47 Å. There are five inequivalent V sites. In the first V site, V is bonded in a 6-coordinate geometry to six O atoms. There are a spread of V–O bond distances ranging from 1.66–2.27 Å. In the second V site, V is bonded in a 6-coordinate geometry to six O atoms. There are a spread of V–O bond distances ranging from 1.63–2.38 Å. In the third V site, V is bonded in a 6-coordinate geometry to six O atoms. There are a spread of V–O bond distances ranging from 1.65–2.31 Å. In the fourth V site, V is bonded to six O atoms to form distorted edge-sharing VO6 octahedra. There are a spread of V–O bond distances ranging from 1.73–2.12 Å. In the fifth V site, V is bonded in a 6-coordinate geometry to six O atoms. There are a spread of V–O bond distances ranging from 1.66–2.38 Å. Co is bonded in an octahedral geometry to six O atoms. There are a spread of Co–O bond distances ranging from 2.02–2.07 Å. There are twenty inequivalent H sites. In the first H site, H is bonded in a single-bond geometry to one O atom. The H–O bond length is 0.98 Å. In the second H site, H is bonded in a single-bond geometry to one O atom. The H–O bond length is 0.99 Å. In the third H site, H is bonded in a single-bond geometry to one O atom. The H–O bond length is 0.98 Å. In the fourth H site, H is bonded in a single-bond geometry to two O atoms. There is one shorter (1.00 Å) and one longer (1.73 Å) H–O bond length. In the fifth H site, H is bonded in a single-bond geometry to one O atom. The H–O bond length is 1.00 Å. In the sixth H site, H is bonded in a single-bond geometry to one O atom. The H–O bond length is 1.00 Å. In the seventh H site, H is bonded in a single-bond geometry to one O atom. The H–O bond length is 0.98 Å. In the eighth H site, H is bonded in a single-bond geometry to one O atom. The H–O bond length is 0.99 Å. In the ninth H site, H is bonded in a single-bond geometry to one O atom. The H–O bond length is 0.99 Å. In the tenth H site, H is bonded in a single-bond geometry to one O atom. The H–O bond length is 0.99 Å. In the eleventh H site, H is bonded in a single-bond geometry to one O atom. The H–O bond length is 0.99 Å. In the twelfth H site, H is bonded in a single-bond geometry to one O atom. The H–O bond length is 1.01 Å. In the thirteenth H site, H is bonded in a single-bond geometry to one O atom. The H–O bond length is 0.99 Å. In the fourteenth H site, H is bonded in a single-bond geometry to one O atom. The H–O bond length is 0.99 Å. In the fifteenth H site, H is bonded in a single-bond geometry to one O atom. The H–O bond length is 0.98 Å. In the sixteenth H site, H is bonded in a single-bond geometry to one O atom. The H–O bond length is 0.99 Å. In the seventeenth H site, H is bonded in a single-bond geometry to one O atom. The H–O bond length is 0.98 Å. In the eighteenth H site, H is bonded in a single-bond geometry to one O atom. The H–O bond length is 0.98 Å. In the nineteenth H site, H is bonded in a single-bond geometry to one O atom. The H–O bond length is 0.99 Å. In the twentieth H site, H is bonded in a single-bond geometry to one O atom. The H–O bond length is 0.98 Å. There are twenty-four inequivalent O sites. In the first O site, O is bonded in a distorted water-like geometry to one Na and two H atoms. In the second O site, O is bonded in a distorted water-like geometry to two Na and two H atoms. In the third O site, O is bonded in a distorted bent 120 degrees geometry to two V atoms. In the fourth O site, O is bonded in a trigonal non-coplanar geometry to three V atoms. In the fifth O site, O is bonded in a distorted water-like geometry to one Co and two H atoms. In the sixth O site, O is bonded in a single-bond geometry to one V atom. In the seventh O site, O is bonded in a distorted trigonal non-coplanar geometry to one Co and two H atoms. In the eighth O site, O is bonded in a distorted water-like geometry to one Na and two H atoms. In the ninth O site, O is bonded in a distorted water-like geometry to two Na and two H atoms. In the tenth O site, O is bonded in a distorted water-like geometry to one Na and two H atoms. In the eleventh O site, O is bonded in a distorted single-bond geometry to one V atom. In the twelfth O site, O is bonded in a distorted trigonal planar geometry to two V and one H atom. In the thirteenth O site, O is bonded in a distorted bent 120 degrees geometry to two V atoms. In the fourteenth O site, O is bonded in a distorted water-like geometry to two Na and two H atoms. In the fifteenth O site, O is bonded in a single-bond geometry to one V atom. In the sixteenth O site, O is bonded in a distorted water-like geometry to two V atoms. In the seventeenth O site, O is bonded in a bent 120 degrees geometry to two V atoms. In the eighteenth O site, O is bonded in a distorted linear geometry to one Na and one V atom. In the nineteenth O site, O is bonded in a bent 120 degrees geometry to two V atoms. In the twentieth O site, O is bonded to six V atoms to form edge-sharing OV6 octahedra. In the twenty-first O site, O is bonded in a trigonal non-coplanar geometry to three V atoms. In the twenty-second O site, O is bonded in a water-like geometry to two V atoms. In the twenty-third O site, O is bonded in a distorted water-like geometry to two Na and two H atoms. In the twenty-fourth O site, O is bonded in a distorted water-like geometry to one Co and two H atoms.
36 MATERIALS SCIENCE↗
Comprehensive Mechanisms of Electrocatalytic CO2 Reduction by [Ir(bip)(ppy)(CH3CN)](PF6)2
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99 GENERAL AND MISCELLANEOUS↗
MM and subMM molecular line observations of the southwest lobe of L1551: Evidence of a shell structure
Observations have been made of the southwest outflow lobe of L1551 in several millimeter and submillimeter molecular lines. Maps have been made in the J=3-2 and J=2-1 transitions of CO over areas of 7.5 by 2.5 arc minutes and 5 by 5 arc minutes respectively at UKIRT. More detailed maps have also been made in the J=2-1 CO transition over an area of about 6 by 3.5 arc minutes at the NRAO 12m telescope. Additional observations of the J=4-3 transitions of HCN, HCO(+) abd H(13)CO(+) were made at selected positions. The HC(+) J=4-3 transition was detected at several positions along the outflow axis and at the position of IRS 5. Similarly the HCN J=4-3 transition was detected at the position of IRS 5 and also at a position close to HH29. However, the J=4-3 transition of H(13)CO(+) was bit detected at the position of IRS 5 even through it was observed at the position close to HH29 with a peak corrected antenna temperature of 0.23K at a V(LSR) of 1 km s(-1). The detection of the J=4-3 transitions of both HCO(+) and H(13)CO(+) close to the position of HH29 suggest the presence of very dense gas in this region. LVG analysis of the various molecular lines observed give a kinetic temperature between 10 and 15K and a density from 10(5) to 10(6) cm(-3) at the position of IRS 5 at the ambient cloud velocity. At the position close to HH29 LVG analysis of the CO observations gives a density between 10(3) and 10(4) cm(-3) at a kinetic temperature of 25k for a V(LSR) of 0 km s(-1). To the southwest of HH29 there is a large decrease in both the linewidth and intensity of CO emission. This may be due to the interaction between the outflow and a dense clump of gas which gives rise to HH29. The maps of the CO J=3-2 and CO J=2-1 emission integrated in 3.25 km s intervals show the shell structure postulated by Snell and Schloerb (1985).
Rainey, R.↗
Photosynthesis of CO from CO 2 with an iron polypyridyl catalyst at a passivated silicon photoelectrode
A first-row transition metal catalyst, [Fe(tpy)(Mebim-py)(NCCH 3 )] 2+ (tpy = 2,2′:6′,2′′-terpyridine, Mebim-py = 1-methylbenzimidazol-2-ylidene-3-(2′-pyridine)) mediates CO 2 reduction to CO at passivated p-Si photoelectrodes with applied potentials 240 mV positive of the standard CO 2 /CO reduction potential. The molecular catalyst's selectivity for CO was retained under photoelectrochemical conditions, with negligible direct proton reduction promoted by the photoelectrode. The faradaic efficiency for CO (44 ± 6%) was slightly enhanced relative to the catalyst performance in the dark (33%). A photosynthetic cell based on this photocathode system, coupled with ferrocene oxidation at the anode, successfully operated at a cell voltage of −1.2 V. The photovoltage generated by illumination of p-Si–CH 3 met and surpassed the potential required for CO 2 reduction when coupled with ferrocene oxidation. By leveraging a low-overpotential CO 2 reduction electrocatalyst, a photo-assisted electrochemical efficiency of 0.15% and applied bias photon-to-current efficiency of 0.05% was achieved for this single-junction cell, ultimately storing 46 kJ mol −1 (11 kcal mol −1 ) of photon energy.
Carbon Dioxide Reduction↗
Electrocatalytic properties of a novel ruthenium( ii ) terpyridine-based complex towards CO 2 reduction
The electrocatalytic properties of Ru complexes are of great technological interest given their potential application in reactions such water splitting and CO 2 reduction. In this work, a novel terpyridine-based Ru(II) complex, [RuCl(trpy)(acpy)], trpy = 2,2':6',2"-terpyridine, acpy - = 2-pyridylacetate was synthesized and its spectroscopic, electrochemical and catalytic properties were explored in detail. In dry acetonitrile, the complex exhibits two reduction peaks at -1.95 V and -2.20 V vs. Fc/Fc + , attributed to consecutive 1 e - reduction. Under CO 2 atmosphere, a catalytic wave is observed (E onset = 2.1 V vs. Fc/Fc + ), with CO as the main reduction product. Bulk electrolysis reveals a turnover number (TON) of 12 (k obs = 1.5 s -1 ). In the presence of 1% water, an improvement in the catalytic activity is observed (TON CO = 21 and k obs = 2.0 s -1 ) and, additionally, formate was also detected (TON HCOO = 7). Spectroelectrochemical experiments allowed the identification of a metallocarboxylate (Ru–COO - ) intermediate under anhydrous conditions, while in water, the partial labilization of the acpy- ligand was observed in the course of the catalytic cycle. The experimental data was combined with DFT calculations, allowing the proposal of a catalytic cycle. Here the results establish important relationships between selectivity, ligand structure and reaction conditions.
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
High Performance SOFCs with a Superior Stability for Reliable and Durable Power Systems
Next generation of fuel cells, electrolyzers, and batteries requires higher power, faster kinetics, and larger energy density, which necessitate the use of compositionally complex oxides to achieve multifunctionalities and activity. These compositionally complex oxides may change their phases and structures during an electrochemical process – a so-called “electrochemically driven phase transformation”. The origin for such a phase change has remained obscure. More importantly, there is a need to develop high performance solid oxide fuel cells with an enhanced stability. In this work, the La 0.6 Sr 0.4 Co 0.2 Fe 0.8 O 3 (LSCF) cathode surface is modified by infiltration of Pr 6 O 11 and the power density at 0.8V and 750 °C is improved by 21%. In addition, by replacing the traditional barrier layer Gd 0.2 Ce 0.8 O 1.9 with mixed conducting Pr 0.1 Gd 0.1 Ce 0.8 O 1.9 , the power density increases by 38%. The different mechanism of promotions was investigated by electrochemical impedance spectroscopy. The ohmic resistance is dramatically reduced by applying the PGCO interlayer, and the distribution of relaxation time was used to analyze the mechanism for which the polarization resistance was decreased attributing to the mixed conduction nature in PrO x . An increase of power density at 0.8 V of 0.358 W/cm 2 (71%) is achieved with the implementation of both surface modification and buffer layer engineering. An experimental study and a theoretical analysis were then carried out on phase evolution in praseodymium nickelates. Nickelate-based electrodes show up to 60× greater phase transformation during operation when compared to thermally annealed ones. Theoretical analysis suggests that the presence of a reduced oxygen partial pressure at the interface between the oxygen electrode and the electrolyte is the origin for the phase change in an oxygen electrode. Guided by the theory, an addition of the electronic conduction in the interface layer leads to the significant suppression of phase change, while improving cell performance and performance stability. When an oxygen electrode is under polarization, the oxygen partial pressure at the interface between the oxygen electrode and the electrolyte is lower than that of incoming oxidant. Under a high polarization, the environment at the aforementioned interface may lead to phase transformation of the oxygen electrode. The local oxygen partial pressure is determined by the transport properties at the interfaces. An addition of the electronic conduction in the interface layer, for instance using (Pr,Gd)-doped ceria to replace Gd-doped ceria, results in improved cell performance and performance stability, while the phase transformation is significantly suppressed. This work provides a fundamental understanding of the origin for phase transformation in oxygen electrodes during operation and use this knowledge to develop a high-performance electrode that exhibits improved performance stability.
30 DIRECT ENERGY CONVERSION↗
Role of mixed conducting Pr 0.1 Gd 0.1 Ce 0.8 O 1.9-δ barrier layer on the promotion of SOFC performance
The cathode activity in a solid oxide fuel cell can be promoted by introducing various catalysts to reduce its polarization resistance towards oxygen reduction, and thus improve cell performance. Here, in this work, the La 0.6 Sr 0.4 Co 0.2 Fe 0.8 O 3 (LSCF) cathode surface is modified by the infiltration of Pr 6 O 11 and the power density at 0.8 V and 750 °C is improved by 21%. Moreover, by replacing the traditional barrier layer Gd 0.2 Ce 0.8 O 1.9 with mixed conducting Pr 0.1 Gd 0.1 Ce 0.8 O 1.9 (PGCO), the power density increases by 38%. The ohmic resistance is dramatically reduced by applying the PGCO interlayer. The distribution of relaxation time was used to analyze the mechanism for which the polarization resistance was decreased, attributing to the mixed conduction nature in PrO x . An increase of power density, ~0.358 W/cm 2 (71%) at 0.8 V, is achieved with the implementation of both surface modification and buffer layer engineering.
08 HYDROGEN↗