BaTiO3-xNy: Highly Basic Oxide Catalyst Exhibiting Coupling of Electrons at Oxygen Vacancies with Substituted Nitride Ions

The base strength of oxide catalysts is controlled by the electron charge distribution between cations and anions, with unsaturated oxygen ions that have lone pair electrons typically acting as basic sites. Substitution of oxide ions with anions that have different valences, such as nitride and hydride ions, can often generate basic sites. It is plausible that electrons trapped at oxygen vacancy sites could provide increased electron density and shift the highest occupied molecular orbital energy levels of anions upward in the case that the oxygen vacancies couple with surface-substituted anions. The present work demonstrates that high catalytic basicity can be obtained via site-selective doping of anions at face-sharing Ti2O9 dimer sites with oxygen vacancies in BaTiO3-x. This improved basicity stems from the coupling of substituted nitride ions to electrons at oxygen vacancies. The oxynitride BaTiO3-xNy was found to contain nitride ions that have increased electronic charge density on the basis of such interactions. Enhanced surface basicity following doping with nitride ion was also confirmed by CO2 temperature-programmed desorption and infrared spectroscopy in conjunction with the adsorption of CHCl3. The strong Lewis base sites resulting from the formation of the oxynitride evidently facilitated the catalytic activation of C-H bonds to promote Knoevenagel condensation reactions between aldehydes and active methylene compounds with pKa values of up to 28.9.

Ammonia Synthesis over Fe-Supported Catalysts Mediated by Face-Sharing Nitrogen Sites in BaTiO3-x Ny Oxynitride

Invited for this Issue's cover is the group of Professor Hideo Hosono at Tokyo Institute of Technology. The Cover image explores the question which activation dominates N2 activation for ammonia synthesis. The Research Article itself is available at 10.1002/cssc.202300551.

Ammonia Synthesis over Fe-Supported Catalysts Mediated by Face-Sharing Nitrogen Sites in BaTiO3-x Ny Oxynitride

Nitride and hydride materials have been proposed as active supports for the loading of transition metal catalysts in thermal catalytic ammonia synthesis. However, the contribution of nitrogen or hydride anions in the support to the catalytic activity for supported transition-metal catalysts is not well understood, especially for Fe-based catalysts. Here, we report that hexagonal-BaTiO3-x Ny with nitrogen vacancies at face-sharing sites acts as a more efficient support for Fe catalysts for ammonia synthesis than BaTiO3 or BaTiO3-x Hx at 260 °C to 400 °C. Isotopic experiments, in situ measurements, and a small inverse isotopic effect in ammonia synthesis have revealed that nitrogen molecules are activated at nitrogen vacancies formed at the interface between Fe nanoparticles and the support. Nitrogen vacancies on BaTiO3-x Ny can promote the activity of Fe and Ni catalysts, while electron donation and suppression of hydrogen poisoning by BaTiO3-x Hx are significant in the Ru and Co systems.

Ammonia Cracking Catalyzed by Ni Nanoparticles Confined in the Framework of CeO2 Support

For the extraction of hydrogen from ammonia at low temperatures, we investigated Ni-based catalysts fabricated by the thermal decomposition of RNi5 intermetallics (R = Ce or Y). The interconnected microstructure formed via phase separation between the Ni catalyst and the resulting oxide support was observed to evolve via low-temperature thermal decomposition of RNi5. The resulting Ni/CeO2 nanocomposite exhibited superior catalytic activity of ∼25% at 400 °C for NH3 cracking. The high catalytic activity was attributed to the interlocking of Ni nanoparticles with the CeO2 framework. The growth of Ni nanoparticles was prevented by this interconnected microstructure, in which the Ni nanoparticles incorporated nitrogen owing to the size effect, whereas Ni does not commonly form nitrides. To the best of our knowledge, this is a unique example of a microstructure that enhances catalytic NH3 cracking.

Multiple reaction pathway on alkaline earth imide supported catalysts for efficient ammonia synthesis

The tunability of reaction pathways is required for exploring efficient and low cost catalysts for ammonia synthesis. There is an obstacle by the limitations arising from scaling relation for this purpose. Here, we demonstrate that the alkali earth imides (AeNH) combined with transition metal (TM = Fe, Co and Ni) catalysts can overcome this difficulty by utilizing functionalities arising from concerted role of active defects on the support surface and loaded transition metals. These catalysts enable ammonia production through multiple reaction pathways. The reaction rate of Co/SrNH is as high as 1686.7 mmol·gCo-1·h-1 and the TOFs reaches above 500 h-1 at 400 °C and 0.9 MPa, outperforming other reported Co-based catalysts as well as the benchmark Cs-Ru/MgO catalyst and industrial wüstite-based Fe catalyst under the same reaction conditions. Experimental and theoretical results show that the synergistic effect of nitrogen affinity of 3d TMs and in-situ formed NH2- vacancy of alkali earth imides regulate the reaction pathways of the ammonia production, resulting in distinct catalytic performance different from 3d TMs. It was thus demonstrated that the appropriate combination of metal and support is essential for controlling the reaction pathway and realizing highly active and low cost catalysts for ammonia synthesis.

A 2D Ba2N Electride for Transition Metal-Free N2 Dissociation under Mild Conditions

N2 activation is a key step in the industrial synthesis of ammonia and other high-value-added N-containing chemicals, and typically is heavily reliant on transition metal (TM) sites as active centers to reduce the large activation energy barrier for N2 dissociation. In the present work, we report that a 2D electride of Ba2N with anionic electrons in the interlayer spacings works efficiently for TM-free N2 dissociation under mild conditions. The interlayer electrons significantly boost N2 dissociation with a very small activation energy of 35 kJ mol-1, as confirmed by the N2 isotopic exchange reaction. The reaction of anionic electrons with N2 molecules stabilizes (N2)2- anions, the so-called diazenide, in the large interlayer space (∼4.5 Å) sandwiched by 2 cationic slabs of Ba2N as the main intermediate.

Topological insulator as an efficient catalyst for oxidative carbonylation of amines

Topological materials have received much attention because of their robust topological surface states, which can be potentially applied in electronics and catalysis. Here, we show that the topological insulator bismuth selenide functions as an efficient catalyst for the oxidative carbonylation of amines with carbon monoxide and dioxygen to synthesize urea derivatives. For example, the carbonylation of butylamine can be completed over bismuth selenide nanoparticle catalyst in 4 hours at 20°C with a yield of 99%, whereas most noble metal-based catalysts do not function at such a low temperature. Density functional theory calculations further reveal that the topological surface states facilitate the activation of dioxygen through a triplet-to-singlet spin-conversion reaction, in which active oxygen species are formed with a barrier of 0.4 electron volts for the subsequent reactions with amine and carbon monoxide.

Boosted Activity of Cobalt Catalysts for Ammonia Synthesis with BaAl2O4-xHy Electrides

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, BaAl₂O_4-xH_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. BaAl₂O_4-xH_y with a stuffed tridymite structure has interstitial cage sites where anionic electrons are accommodated. The surface of BaAl₂O_4-xH_y with very low work functions (1.7-2.6 eV) can donate electrons strongly to Co, which largely facilitates N₂ reduction into ammonia with the aid of the lattice H^- ions. The stuffed tridymite structure of BaAl₂O_4-xH_y with a three-dimensional AlO₄-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.

Room-Temperature CO2 Hydrogenation to Methanol over Air-Stable hcp-PdMo Intermetallic Catalyst

CO₂ hydrogenation to methanol is one of the most promising routes to CO₂ utilization. However, difficulty in CO₂ 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 CO₂ 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 CO₂ 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).

Electronic Promotion of Methanol Synthesis over Cu-Loaded ZnO-Based Catalysts

Methanol, a raw material for C1 chemistry, is industrially produced under harsh conditions using Cu/ZnO-based catalysts. The synthesis of methanol under mild conditions is a challenging subject using an improved catalyst. Here, Zn_1-xSi_xO (ZSO) nanoparticles were synthesized by a thermal plasma method, and their work function and carrier concentration could be tuned by the Zn:Si ratio. The electrically conductive ZSO nanoparticles with a low work function enhanced the donation of electrons to loaded Cu and significantly promoted hydrogenation of CO to methanol, whereas insulating ZSO nanoparticles with a similar low work function did not. These results reveal that efficient electronic promotion by the transfer of electrons from a support to loaded Cu plays a key role in low-temperature methanol synthesis.

Unique Catalytic Mechanism for Ru-Loaded Ternary Intermetallic Electrides for Ammonia Synthesis

Intermetallic electrides have recently shown their priority as catalyst components in ammonia synthesis and CO₂ activation. However, their function mechanism has been elusive since its inception, which hinders the further development of such catalysts. In this work, ternary intermetallic electrides La-TM-Si (TM = Co, Fe, and Mn) were synthesized as hosts of ruthenium (Ru) particles for ammonia synthesis catalysis. Although they have the same crystal structure and possess low work functions commonly, the promotion effects on Ru particles rather differ from each other. The catalytic activity follows the sequence of Ru/LaCoSi > Ru/LaFeSi > Ru/LaMnSi. Furthermore, Ru/LaCoSi exhibits much better catalytic durability than the other two. A combination of experiments and first-principles calculations shows that apparent N₂ activation energy on each catalyst is much lower than that over conventional Ru-based catalysts, which suggests that N₂ dissociation can be conspicuously promoted by the concerted actions of the specific electronic structure and atomic configuration of intermetallic electride-supported catalysts. The NH_x formations proceeded on La are energetically favored, which makes it possible to bypass the scaling relations based on only Ru as the active site. The rate-determining step of Ru/La-TM-Si was identified to be NH₂ formation. The transition metal (TM) in La-TM-Si electrides has a significant influence on the metal-support interaction of Ru and La-TM-Si. These findings provide a guide for the development of new and effective catalyst hosts for ammonia synthesis and other hydrogenation reactions.

Hexagonal BaTiO(3-x)Hx Oxyhydride as a Water-Durable Catalyst Support for Chemoselective Hydrogenation

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 (P6₃/mmc) was synthesized by the direct reaction of BaH₂ and TiO₂ at 800 °C under a stream of hydrogen, and the estimated chemical composition was BaTiO_2.01H_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.

Dissociative and Associative Concerted Mechanism for Ammonia Synthesis over Co-Based Catalyst

The current catalytic reaction mechanism for ammonia synthesis relies on either dissociative or associative routes, in which adsorbed N₂ dissociates directly or is hydrogenated step-by-step until it is broken upon the release of NH₃ through associative adsorption. Here, we propose a concerted mechanism of associative and dissociative routes for ammonia synthesis over a cobalt-loaded nitride catalyst. Isotope exchange experiments reveal that the adsorbed N₂ can be activated on both Co metal and the nitride support, which leads to superior low-temperature catalytic performance. The cooperation of the surface low work function (2.6 eV) feature and the formation of surface nitrogen vacancies on the CeN support gives rise to a dual pathway for N₂ activation with much reduced activation energy (45 kJ·mol^-1) over that of Co-based catalysts reported so far, which results in efficient ammonia synthesis under mild conditions.

Ship-in-a-Bottle Synthesis of High Concentration of N2 Molecules in a Cage-Structured Electride

We report the formation of neutral nitrogen molecules in the cages of [Ca₁₂Al₁₄O₃₂]²⁺ (C12A7) framework compensated by extra-framework anions. NH₃ treatment of C12A7 electride (C12A7:e^-) at 800 °C leads to the formation of N₂ and NH^2- species in the C12A7 cages. N₂ and NH_x species in the cages are identified using the Raman spectroscopy of ¹⁴NH₃ and ¹⁵NH₃-treated C12A7:e^-. The concentration of H and N in the C12A7 cages after NH₃ treatment is ∼10²¹ cm^-3. We propose a two-step mechanism, supported by density functional theory (DFT) modeling, of N₂ incorporation into the C12A7 cages, i.e., incorporation of NH^2- formed from decomposition of NH₃ at C12A7:e^- surface followed by the NH^2- species reacting to form N₂ molecules. Encapsulation of neutral molecules, as opposed to negatively charged species reported in C12A7 previously, offers new opportunities for trapping and storing gaseous substances in nanoporous materials.

Contribution of Nitrogen Vacancies to Ammonia Synthesis over Metal Nitride Catalysts

Ammonia is one of the most important feedstocks for the production of fertilizer and as a potential energy carrier. Nitride compounds such as LaN have recently attracted considerable attention due to their nitrogen vacancy sites that can activate N₂ for ammonia synthesis. Here, we propose a general rule for the design of nitride-based catalysts for ammonia synthesis, in which the nitrogen vacancy formation energy (E_NV) dominates the catalytic performance. The relatively low E_NV (ca. 1.3 eV) of CeN means it can serve as an efficient and stable catalyst upon Ni loading. The catalytic activity of Ni/CeN reached 6.5 mmol·g^-1·h^-1 with an effluent NH₃ concentration (E_NH3) of 0.45 vol %, reaching the thermodynamic equilibrium (E_NH3 = 0.45 vol %) at 400 °C and 0.1 MPa, thereby circumventing the bottleneck for N₂ activation on Ni metal with an extremely weak nitrogen binding energy. The activity far exceeds those for other Co- and Ni-based catalysts, and is even comparable to those for Ru-based catalysts. It was determined that CeN itself can produce ammonia without Ni-loading at almost the same activation energy. Kinetic analysis and isotope experiments combined with density functional theory (DFT) calculations indicate that the nitrogen vacancies in CeN can activate both N₂ and H₂ during the reaction, which accounts for the much higher catalytic performance than other reported nonloaded catalysts for ammonia synthesis.

SAT0546 COMPARISON OF SHEAR WAVE ELASTOGRAPHY AND CONVENTIONAL ULTRASONOGRAPHY OF SALIVARY GLANDS IN PATIENTS WITH PRIMARY SJOGREN’S SYNDROME: CAN SHEAR WAVE ELASTOGRAPHY CAPTURE LESIONS THAT ARE DIFFICULT TO DIAGNOSE WITH CONVENTIONAL ULTRASONOGRAPHY?

Background:

Sjögren’s syndrome (SS) is a chronic inflammatory autoimmune disease characterized by lymphocyte infiltration in salivary and lacrimal glands. Recently, salivary gland ultrasonography (US) proved valuable for assessing salivary gland involvement in SS and seemed to exhibit good diagnostic properties. In the literature, studies conducted by the scoring of the structural changes according to B-Mode US of salivary glands showed a wide variability regarding sensitivity and specificity. Our previously study demonstrated that although conventional B-mode US findings were useful for the diagnosis of SS with low salivary flow they were not for subclinical SS with normal salivary flow (EULAR 2016). Recently, we reported that the tissue elasticity was decreased due to structural changes in the submandibular glands (SG) at the advanced stage of the disease and the shear wave elastography (SWE) is useful to distinguish pathological changes of the SG in patients with SS (EULAR2018).

Objectives:

The aim of this study was to compare the usefulness of SG conventional B-mode US and SWE findings in non-SS and SS patients classified by salivary flow.

Methods:

Twenty-two non-SS patients and 99 SS patients who fulfilled the American College of Rheumatology (ACR) / European League Against Rheumatism (EULAR) classification criteria for SS were studied. SS patients were divided into three groups according to salivary flow using gum test (VL/SS <5mL/10min. (n=38), L/SS 5-10mL/10min. (n=41) and N/SS >10mL/10min. (n=20)). All patients were examined SGUS by a single investigator who was blinded to device (TUS-A300; Canon Medical Systems, Tokyo, Japan) with a linear transducer (7.5-10MHz). The examination consisted of conventional B-mode US (US staging score), pulsed wave Doppler US (PD grading score) and SWE with quantitative assessment. US staging scores were assessed by glandular size, inhomogeneity and contrast of diagastric muscle (stage 0 to 3). PD grading scores were graded by pulsed wave pattern in pulsed wave Doppler US at the internal SG facial arteries (grade 0 to 2). With the region-of-interest (ROI) placed over the stiffest areas of the lesion on SWE, the quantitative means of the elasticity values were measured by shear wave velocity (Vs; m/s) and elasticity (E; kPa) for each lesion.

Results:

The US staging score, the PD grading score, the values of Vs and E were significantly higher in patients with SS than in non-SS group (SS vs non-SS; US staging score 2.10±1.07 vs 0.86±0.99, p<0.0001, PD grading score 1.17±0.83 vs 0.23±0.61, p<0.0001, Vs 1.75±0.34 vs 1.57±0.29m/s, p=0.02, E 9.64±4.02 vs 7.81±2.27kPa, p=0.04). However, there was no significant difference between non-SS and N/SS in early-stage SS by US staging score (N/SS vs non-SS; 0.95±0.89 vs 0.86±0.99) and PD grading score (N/SS vs non-SS; 0.40±0.15 vs 0.23±.061). In contrast, the values of Vs and E were highest in N/SS as compared with all groups, and were significantly higher in N/SS than in non-SS (N/SS vs non-SS; Vs 2.02±0.24 vs 1.57±0.29m/s, p<0.01, E 12.58±3.16 vs 7.81±2.27kPa, p<0.01).

Conclusion:

The present study demonstrated that although the tissue elasticity was decreased due to structural changes at the advanced stage, it increased due to inflammation and high viscosity in the SG at the subclinical SS with normal salivary flow comparing that in non-SS patients. The SWE may be a useful tool for the differential diagnosis between patients with non-SS and subclinical SS with normal salivary flow, which is difficult to distinguish by conventional B-mode US.

Disclosure of Interests:

None declared

Palladium-bearing intermetallic electride as an efficient and stable catalyst for Suzuki cross-coupling reactions

Suzuki cross-coupling reactions catalyzed by palladium are powerful tools for the synthesis of functional organic compounds. Excellent catalytic activity and stability require negatively charged Pd species and the avoidance of metal leaching or clustering in a heterogeneous system. Here we report a Pd-based electride material, Y3Pd2, in which active Pd atoms are incorporated in a lattice together with Y. As evidenced from detailed characterization and density functional theory (DFT) calculations, Y3Pd2 realizes negatively charged Pd species, a low work function and a high carrier density, which are expected to be beneficial for the efficient Suzuki coupling reaction of activated aryl halides with various coupling partners under mild conditions. The catalytic activity of Y3Pd2 is ten times higher than that of pure Pd and the activation energy is lower by nearly 35%. The Y3Pd2 intermetallic electride catalyst also exhibited extremely good catalytic stability during long-term coupling reactions.

Low-Temperature Synthesis of Perovskite Oxynitride-Hydrides as Ammonia Synthesis Catalysts

Mixed anionic materials such as oxyhydrides and oxynitrides have recently attracted significant attention due to their unique properties, such as fast hydride ion conduction, enhanced ferroelectrics, and catalytic activity. However, high temperature (≥800 °C) and/or complicated processes are required for the synthesis of these compounds. Here we report that a novel perovskite oxynitride-hydride, BaCeO_3-xN_yH_z, can be directly synthesized by the reaction of CeO₂ with Ba(NH₂)₂ at low temperatures (300-600 °C). BaCeO_3-xN_yH_z, with and without transition metal nanoparticles, functions as an efficient catalyst for ammonia synthesis through the lattice N^3- and H^- ion-mediated Mars-van Krevelen mechanism, while ammonia synthesis occurs over conventional catalysts through a Langmuir-Hinshelwood mechanism with high energy barriers (85-121 kJ mol^-1). As a consequence, the unique reaction mechanism leads to enhancement of the activity of BaCeO₃-based catalysts by a factor of 8-218 and lowers the activation energy (46-62 kJ mol^-1) for ammonia synthesis. Furthermore, isotopic experiments reveal that this catalyst shifts the rate-determining step for ammonia synthesis from N₂ dissociation to N-H bond formation.

Acid-durable electride with layered ruthenium for ammonia synthesis: boosting the activity via selective etching

We reported LnRuSi as a B₅-site-free Ru catalyst for ammonia synthesis, and its activity enhanced 2–4-fold by selective etching with EDTA-2Na.

Ruthenium (Ru) loaded catalysts are of significant interest for ammonia synthesis under mild reaction conditions. The B₅ sites have been reported as the active sites for ammonia formation, i.e., Ru with other coordinations were inactive, which has limited the utilization efficiency of Ru metal. The implantation of Ru into intermetallic compounds is considered to be a promising approach to tune the catalytic activity and utilization efficiency of Ru. Here we report an acid-durable electride, LnRuSi (Ln = La, Ce, Pr and Nd), as a B₅-site-free Ru catalyst. The active Ru plane with a negative charge is selectively exposed by chemical etching using disodium dihydrogen ethylenediaminetetraacetate (EDTA-2Na) acid, which leads to 2–4-fold enhancement in the ammonia formation rate compared with that of the original catalyst. The turnover frequency (TOF) of LnRuSi is estimated to be approximately 0.06 s^–1, which is 600 times higher than that of pure Ru powder. Density functional theory (DFT) calculations revealed that the dissociation of N₂ occurs easily on the exposed Ru plane of LaRuSi. This systematic study provides firm evidence that layered Ru with a negative charge in LnRuSi is a new type of active site that differs significantly from B₅ sites.

Pseudogap Control of Physical and Chemical Properties in CeFeSi-Type Intermetallics

We describe the synthesis of the new ternary compound CaRuSi whose chemical and physical properties help draw a clear picture of how electronic structure controls the behavior of an isostructural series of intermetallics. DFT calculations reveal that an electronic pseudogap arises near the Fermi level ( E_F), corresponding to 14 valence electrons per RuSi unit. The closed-shell-like character is further investigated by comparisons with the electronic structures of CaCoSi (15 electrons), where the E_F lies above the corresponding pseudogap, and its hydride CaCoSiH, where formation of H anions restores the 14-electron count on the metal sublattice, returning the E_F to the pseudogap. The chemical origin of the 14-electron pseudogap is interpreted with a reversed approximation Molecular Orbital analysis. Here, the pseudogap is shown to coincide with the filling of Ru 16 electron configurations isolobal to the d⁸ square planar complexes of coordination chemistry (but where 4 electron pairs are shared covalently between Ru atoms such that only 12 electrons are required), and the occupation of Si lone pairs (2 electrons). Experimentally, the pseudogap is confirmed with heat capacity measurements, which indicate that the 14-electron systems CaRuSi and CaCoSiH each exhibit  a smaller electronic density of states at the E_F than the 15-electron system CaCoSi. Importantly, the 14-electron pseudogap also significantly affects the chemical properties of the compounds, as evidenced by the difference in the stabilities of CaCoSiH and CaRuSiH observed in hydrogen desorption measurements. These results may support the design of functional materials for superconductivity, hydrogen storage, and catalysis involving hydrogenation.

High-Mobility p-Type and n-Type Copper Nitride Semiconductors by Direct Nitriding Synthesis and In Silico Doping Design

Thin-film photovoltaics (PV) have emerged as a technology that can meet the growing demands for efficient and low-cost large-scale cells. However, the photoabsorbers currently in use contain expensive or toxic elements, and the difficulty in bipolar doping, particularly in a device structure, requires elaborate optimization of the heterostructures for improving the efficiency. This study shows that bipolar doping with high hole and electron mobilities in copper nitride (Cu₃ N), composed solely of earth-abundant and environmentally benign elements, is readily available through a novel gaseous direct nitriding reaction applicable to uniform and large-area deposition. A high-quality undoped Cu₃ N film is essentially an n-type semiconductor, while p-type conductivity is realized by interstitial fluorine doping, as predicted using density functional theory calculations and directly proven by atomically resolved imaging. The synthetic methodology for high-quality p-type and n-type films paves the way for the application of Cu₃ N as an alternative absorber in thin-film PV.

A high performance catalyst of shape-specific ruthenium nanoparticles for production of primary amines by reductive amination of carbonyl compounds

The creation of metal catalysts with highly active surfaces is pivotal to meeting the strong economic demand of the chemical industry. Specific flat-shaped pristine fcc ruthenium nanoparticles having a large fraction of atomically active {111} facets exposed on their flat surfaces have been developed that act as a highly selective and reusable heterogeneous catalyst for the production of various primary amines at exceedingly high reaction rates by the low temperature reductive amination of carbonyl compounds. The high performance of the catalyst is attributed to the large fraction of metallic Ru serving as active sites with weak electron donating ability that prevail on the surface exposed {111} facets of flat-shaped fcc Ru nanoparticles. This catalyst exhibits a highest turnover frequency (TOF) of ca. 1850 h-1 for a model reductive amination of biomass derived furfural to furfurylamine and provides a reaction rate approximately six times higher than that of an efficient and selective support catalyst of Ru-deposited Nb2O5 (TOF: ca. 310 h-1).

Copper-Based Intermetallic Electride Catalyst for Chemoselective Hydrogenation Reactions

The development of transition metal intermetallic compounds, in which active sites are incorporated in lattice frameworks, has great potential for modulating the local structure and the electronic properties of active sites, and enhancing the catalytic activity and stability. Here we report that a new copper-based intermetallic electride catalyst, LaCu_0.67Si_1.33, in which Cu sites activated by anionic electrons with low work function are atomically dispersed in the lattice framework and affords selective hydrogenation of nitroarenes with above 40-times higher turnover frequencies (TOFs up to 5084 h^-1) than well-studied metal-loaded catalysts. Kinetic analysis utilizing isotope effect reveals that the cleavage of the H-H bond is the rate-determining step. Surprisingly, the high carrier density and low work function (LWF) properties of LaCu_0.67Si_1.33 enable the activation of hydrogen molecules with extreme low activation energy (E_a = 14.8 kJ·mol^-1). Furthermore, preferential adsorption of nitroarenes via a nitro group is achieved by high oxygen affinity of LaCu_0.67Si_1.33 surface, resulting in high chemoselectivity. The present efficient catalyst can further trigger the hydrogenation of other oxygen-containing functional groups such as aldehydes and ketones with high activities. These findings demonstrate that the transition metals incorporated in the specific lattice site function as catalytically active centers and surpass the conventional metal-loaded catalysts in activity and stability.

Tiered Electron Anions in Multiple Voids of LaScSi and Their Applications to Ammonia Synthesis

Electrides-compounds in which electrons localized in interstitial spaces periodically serve as anions-have attracted broad attention for their exotic properties, such as extraordinary electron-donating ability. In our efforts to expand this small family of phases, LaScSi emerges as a promising candidate. Its electron count is 2e^- f.u.^-1 in excess of that expected from the Zintl concept, while its structure offers interstitial spaces that can accommodate these extra electrons. Herein, this potential is explored through density functional theory (DFT) calculations and property measurements on LaScSi. DFT calculations (validated by heat capacity and electrical transport measurements) reveal electron density peaks at two symmetry-distinct interstitial sites. Importantly, this electride-like character is combined with chemical stability in air and water, an advantage for catalysis. Ru-loaded LaScSi shows outstanding catalytic activity for ammonia synthesis, with a turnover frequency (0.1 s^-1 at 0.1 MPa, 400 °C) an order of magnitude higher than those of oxide-based Ru catalysts, e.g., Ru/MgO. As with other electrides, LaScSi's ability to reversibly store hydrogen prevents the hydrogen poisoning of Ru surfaces. The better performance of LaScSi, however, hints at the importance of the high concentration (>1.6 × 10²² cm^-3 ) and tiered nature of its anionic electrons, which offers guidance toward new catalysts.

Influence of tumor size on outcomes following pelvic exenteration

OBJECTIVE

Pelvic exenteration (PE) is often the only curative option for locally advanced or recurrent pelvic malignancies. Despite radical surgery, recurrence risk and morbidity remain high. In this study, we sought to determine tumor size effect on perioperative outcomes and subsequent survival in patients undergoing PE.

METHODS

Retrospective chart review was performed for female patients who underwent PE at two comprehensive cancer centers from 2000 to 2015. Demographics, complications and outcomes were recorded. Statistical analyses were performed using chi-square, student's t-test, logistic regression, non-parametric tests, log-rank test, and Cox proportional hazards.

RESULTS

Of 151 women who underwent PE, 144 had available pathologic tumor size. Gynecologic oncology, surgical oncology, and urology performed 84, 29, and 31 exenterations, respectively. Tumor dimensions ranged from 0 to 25.5cm. Perioperative complications, 30-day mortality, reoperation, and readmission rates were not associated with tumor size. Obesity and prior radiation increased risk for major perioperative complication while anterior exenterations decreased risk. Larger tumors were more likely to undergo total pelvic exenteration (OR 1.14; 95%CI 1.03-1.27), have positive margins (OR 1.11; 95%CI 1.02-1.22), and recur (65%, 42% and 20% for tumors >4cm, ≤4cm and no residual tumor respectively, p=0.016). Tumor size >4cm and positive margins were associated with worse overall survival amongst gynecologic oncology patients.

CONCLUSION

Tumor size was not associated with perioperative morbidity. Larger tumors were associated with positive margins, more extensive resection, and worse survival in gynecologic oncology patients. Larger studies are needed to further understand tumor size impact on PE outcomes within specific tumor types.