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Extensive first-principles theory calculations predict the possibility of a series of novel heptacoordinate Ni-decorated cage-like metallo-borospherenes and one-dimensional multiple-helix metallo-boronanotubes composed of interconnected boron double chains.

Extensive first-principles theory calculations predict a series of lanthanide/actinide boride nanoclusters and 1D, 2D, and 3D actinide boride nanomaterials based on boron frameworks composed of inverse sandwiched conjoined Bn rings (n = 7–9).

Extensive first-principles theory calculations predict the perfect endohedral metallo-borospherene D3h La@[La5&B30] (1) and its monoanion Cs La@[La5&B30]− (2) and dianion D3h La@[La5&B30]2− (3) which appear to be spherically aromatic in nature.

The high concentration of OVs and active sites of S0.9TF promote its high NRR activity. The proton-conducting solid oxide electrolysis cells (PCECs) with S0.9TF material as a cathode showed a high output (bar) and durability (line).

Extensive density functional theory calculations present a bilayer bottom-up approach from medium-sized boron nanoclusters to semiconducting borophene nanomaterials composed of conjoined B72 bilayer hexagonal prisms sharing boron triple chains.

Searching for the maximum coordination number (CN) in planar species with novel bonding patterns has fascinated chemists for many years. Using the experimentally observed cyclo[18]carbon D9h C18 and theoretically predicted cyclo[14]carbon D7h C14 as effective ligands and based on extensive first-principles theory calculations, we predict herein their perfect planar alkaline-metal-doped complexes D9h Cs©C18+ (1) and D7h Na©C14+ (4) which, as the global minima of the systems with an alkaline metal atom located exactly at the center, possess the record coordination numbers of CN = 18 and 14 in planar species, respectively. More interestingly, detailed energy decomposition and adaptive natural density partitioning bonding analyses indicate that the hypercoordinate alkaline-metal centers in these σ + π dually aromatic complexes exhibit obvious transition metal behaviors, with effective in-plane (π-6s)σ, (π-7p)σ, and (π-5d)σ coordination bonds formed in Cs©C18+ (1) and (π-3s)σ, (π-3p)σ, and (π-3d)σ coordination interactions fabricated in Na©C14+ (4) to dominate the overall attractive interactions between the metal center and its cyclo[n]carbon ligand. Similar dually aromatic alkaline-metal-centered planar Cs Cs©C17B (2), C2v Cs©C17- (3), C2v Na©C13B (5), and C2v Na©C13- (6) have also been obtained with CN = 18, 17, 14, and 13, respectively.

Two-dimensional (2D) borophene has attracted tremendous interest due to its fascinating properties, which have potential applications in catalysts, energy storage devices, and high-speed transistors. In the past few years, borophene was theoretically predicted as an ideal electrode material for lithium-sulfur (Li-S) batteries because of its low-density, metallic conductivity, high Li-ion surface mobility, and strong interface bonding energy to polysulfide. But until now, borophene-based Li-S batteries have not yet been achieved in experiments due to the absence of a large-scale synthetic method of freestanding borophene nanostructures with a high enough structural stability, conductivity, and uniformity. Herein, we developed a low-temperature liquid exfoliation (LTLE) method to synthesize freestanding few-layer β12-borophene single-crystalline sheets with a P6¯m2 symmetry in tens of milligrams. The as-synthesized 2D sheets were used as the polysulfide immobilizers and electrocatalysts of Li-S batteries. The resulting borophene-based Li-S battery delivered an extralarge areal capacity of 5.2 mAh cm-2 at a high sulfur loading of 7.8 mg cm-2, an excellent rate performance of 8 C (@721 mAh g-1), and an ultralow capacity fading rate of 0.039% in 1000 cycles, outperforming commercial Li-ion batteries and many other 2D material-based Li-S batteries. Based on the density functional theory model, the excellent electrochemical performances of the borophene-based Li-S batteries should originate from the enormous enhancement of β12-borophene sheets for both the surface migration of the Li-ions and the adsorption energy of Li2Sn clusters. Our results thus demonstrate a great potential for scalable production of freestanding β12-borophene single-crystalline sheets in future high-performance Li-S batteries.

Boron and boron-based nanoclusters exhibit unique structural and bonding patterns in chemistry. Extensive density functional theory calculations performed in this work predict the mononuclear walnut-like Ci C50B54 (1) (C2B10@C48B44), C1 C50B54 (2) (CB11@C49B43), and S10 C50B54 (3) (B12@C50B42) which contain one icosahedral-CnB12-n core (n = 0, 1, 2) at the center following the Wade’s skeletal electron counting rules and the approximately electron sufficient binuclear peanut-like Cs C88B78 (4) ((C2B10)2@C84B58), Cs C88B78 (5) ((CB11)2@C86B56), Cs C88B78 (6) ((B12)2@C88B54), Cs B180 (7) ((B12)2@B156), Cs B182 (8) ((B12)2@B158), and Cs B184 (9) ((B12)2@B160) which encapsulate two interconnected CnB12-n icosahedrons inside. These novel core-shell borafullerene and borospherene nanoclusters appear to be the most stable species in thermodynamics in the corresponding cluster size ranges reported to date. Detailed bonding analyses indicate that the icosahedral B122-, CB11-, and C2B10 cores in these core-shell structures possess the superatomic electronic configuration of 1S21P61D101F8, rendering spherical aromaticity and extra stability to the systems. Such superatomic icosahedral-CnB12-n stuffed borafullerenes and borospherenes with spherical aromaticity may serve as embryos to form bulk boron allotropes and their carbon-boron binary counterparts in bottom-up approaches.

Boron and boron-based nanoclusters exhibit unique structural and bonding patterns in chemistry. Extensive density functional theory calculations performed in this work predict the mononuclear walnut-like C

Novel lanthanide boride complexes with unique structural and bonding patterns have been observed in recent experiments. Based on extensive first-principles theory calculations, we predict herein the possible existence of half-sandwich C2v LaB14− (1), C1 LaB15 (2), C5v LaB16− (3), and Cs LaB17 (4) which all contain a La center coordinated by a bowl-like Bn ligand (n = 14–17). Detailed bonding analyses indicate that effective d-p coordination interactions exist between the La center and Bn ligand, making these half-sandwich complexes π dually aromatic in nature. Energy decomposition analyses reveal that electrostatic (50.2%) and covalent (49.8%) interactions contribute almost equally to the overall attraction in LaB14− (1), with the La centre serving as both electron donor and acceptor. Molecular dynamics simulations show that both LaB14− (1) (La[B4©B10]−) and LaB17 (4) (La[B©B5©B11]) with multicenter fluxional bonds behave like Wankel motors at finite temperatures.

Cage-like metallo-borospherenes exhibit unique structures and bonding. Inspired by the newly reported smallest spherical trihedral metallo-borospherene D3h Ta3B12– (1), which contains two equivalent B3 triangles interconnected by three B2 units on the cage surface, we present herein a first-principles theory prediction of the perfect spherical tetrahedral metallo-borospherene Td Ta4B18 (2), which possesses four equivalent B3 triangles interconnected by six B atoms, with four equivalent nonacoordinate Ta centers in four η9-B9 rings as integrated parts of the cage surface. As the well-defined global minimum of the neutral, Ta4B18 (2) possesses four 10c-2e B9(π)–Ta(dσ) and eight 10c-2e B9(π)–Ta(dδ) coordination bonds evenly distributed over four Ta-centered Ta@B9 nonagons, with the remaining 18 valence electrons in nine 22c-2e totally delocalized bonds following the 18-electron principle (1S21P61D10) of a superatom. Such a bonding pattern renders spherical aromaticity to the tetrahedral complex, which can be used as building blocks to form the face-centered cubic crystal Ta4B15 (3). The IR, Raman, and UV–vis spectra of Ta4B18 (2) are theoretically simulated to facilitate its future experimental characterizations.

Boron allotropes are known to be predominately constructed by icosahedral B12 cages, while icosahedral-B12 stuffing proves to effectively improve the stability of fullerene-like boron nanoclusters in the size range between B98–B102. However, the thermodynamically most stable core-shell borospherenes with a B12 icosahedron at the center still remains unknown. Based on the structural motif of D5h C70 and extensive first-principles theory calculations, we predict herein the high-symmetry C5v B111+ (3) which satisfies the Wade’s n+1 and n+2 skeletal electron counting rules exactly and the approximately electron sufficient Cs B111 (4), Cs B112 (5), Cs B113 (6), and Cs B114 (7) which are the most stable neutral core-shell borospherenes with a B12 icosahedron at the center reported to date in the size range between B68–B130, with Cs B112 (5) being the thermodynamically most favorite species in the series. Detailed orbital and bonding analyses indicate that these spherically aromatic species all contain a negatively charged icosahedral B122− core at the center which exhibits typical superatomic behaviors in the electronic configuration of 1S21P61D101F8, with its dangling valences saturated by twelve radial B-B 2c-2e σ bonds between the B12 inner core and the B70 outer shell. The infrared (IR) and Raman spectra of the concerned species are computationally simulated to facilitate their future characterizations.

La-[B2@B18]-La demonstrates decisive changes of the properties of molecular rotors, from multiple (here 18) equivalent individual global minimum structures to a quantum mechanical unified structure. This affects their geometries, their symmetries (18*C2h → D9d), the generation of energy bands, and high-resolution spectroscopy.

Size-selected negatively-charged boron clusters (Bn−) have been found to be planar or quasi-planar in a wide size range. Even though cage structures emerged as the global minimum at B39−, the global minimum of B40− was in fact planar. Only in the neutral form did the B40 borospherene become the global minimum. How the structures of larger boron clusters evolve is of immense interest. Here we report the observation of a bilayer B48− cluster using photoelectron spectroscopy and first-principles calculations. The photoelectron spectra of B48− exhibit two well-resolved features at low binding energies, which are used as electronic signatures to compare with theoretical calculations. Global minimum searches and theoretical calculations indicate that both the B48− anion and the B48 neutral possess a bilayer-type structure with D2h symmetry. The simulated spectrum of the D2h B48− agrees well with the experimental spectral features, confirming the bilayer global minimum structure. The bilayer B48−/0 clusters are found to be highly stable with strong interlayer covalent bonding, revealing a new structural type for size-selected boron clusters. The current study shows the structural diversity of boron nanoclusters and provides experimental evidence for the viability of bilayer borophenes.

Vanadium cluster anions are highly reactive making the preparation of pure Vn- and the observation of their reactivity extremely challenging. Herein, well-resolved anionic Vn- clusters are prepared enabling an in-depth study on their reactions with O2 in the gas phase. While pure metal clusters of a magic number are not identified due to the strong V-O bonding, interestingly an unexpected oxide V11O15- was experimentally observed in surviving O2 etching reactions. First-principles theory calculations indicate that V11O15- possesses a body-centered pentagonal prism structure (D5h, ), with the V@V10 core fully protected by 15 oxygen bridges. Such an oxygen-protected metal cluster [V@V10O15]- exhibits typical superatom orbital features pertaining to the V@V10 core which shows effective metal-metal coordination bonding. Meanwhile, the high stability of [V@V10O15]- is reinforced by the V-O-V conjugation interactions which help to maintain the structural integrity, resulting in 3D inorganic aromaticity. This finding of such an oxygen-passivated superatom cluster sheds light on the bonding nature in ligand-protected metal clusters via wet synthesis.

Boron displays many unusual structural and bonding properties due to its electron deficiency. Here we show that a boron atom in a boron monoxide cluster (B9O−) exhibits transition-metal-like properties. Temperature-dependent photoelectron spectroscopy provided evidence of the existence of two isomers for B9O−: the main isomer has an adiabatic detachment energy (ADE) of 4.19 eV and a higher energy isomer with an ADE of 3.59 eV. The global minimum of B9O− is found surprisingly to be an umbrella-like structure (C6v, 1A1) and its simulated spectrum agrees well with that of the main isomer observed. A low-lying isomer (Cs, 1A′) consisting of a BO unit bonded to a disk-like B8 cluster agrees well with the 3.59 eV ADE species. The unexpected umbrella-like global minimum of B9O− can be viewed as a central boron atom coordinated by a η7-B7 ligand on one side and a BO ligand on the other side, [(η7-B7)-B-BO]−. The central B atom is found to share its valence electrons with the B7 unit to fulfill double aromaticity, similar to that in half-sandwich [(η7-B7)-Zn-CO]− or [(η7-B7)-Fe(CO)3]− transition-metal complexes. The ability of boron to form a half-sandwich complex with an aromatic ligand, a prototypical property of transition metals, brings out new metallomimetic properties of boron.

Understanding metal–water interactions and hydrogen-bonding in water droplets is important but highly challenging. Various transition metals may serve as effective coordination centers to water; however, not in all cases is water bonded to a metal center as single molecules. We report here the observations of gas-phase rhodium clusters and their interactions with water. A series of rhodium–water clusters, Rhn±,0(H2O)m (n = 3–30, m = 1–5), with isotope labels were detected by mass spectrometry after exposure to different water concentrations, among which Rh8+(H2O)4 and Rh9+(H2O)3 were prominent in the mass distributions, showing a size-dependent preference of water adsorption on rhodium clusters. Comprehensive density functional theory calculations reveal that the lowest energy structure of Rh9+(H2O)3 possesses a hydrogen-bonded cyclic (H2O)3 water trimer on the top of a tri-capped Rh9+ trigonal prism. The tri-capped Rh9+ trigonal prism and the cyclic (H2O)3 water trimer match in sizes, charge distributions, and orbital symmetries to form effective electrostatic cluster–cluster interactions. In contrast, Rh8+(H2O)4 contains four water molecules separately attached to a bi-capped octahedron, Rh8+, at four corners via single-molecule adsorption. The difference between covalent molecular adsorption and electrostatic cluster–cluster interaction in these two proto-typical rhodium hydrates is further demonstrated by detailed natural bonding orbital, electrostatic surface potential, and charge decomposition analyses.

Monolayer borophenes tend to be easily oxidized, while thicker borophenes have stronger antioxidation properties. Herein, we proposed four novel metallic boron crystals by stacking the experimentally synthesized borophenes, and one of the crystals has been reported in our previous experiments. Bilayer units tend to act as blocks for crystals as determined by bonding analyses. Their kinetic, thermodynamic and mechanical stabilities are confirmed by our calculated phonon spectra, molecular dynamics and elastic constants. Our proposed allotropes are more stable than the boron α-Ga phase below 1000 K at ambient pressure. Some of them become more stable than the α-rh or γ-B

The oxidation stability of borophene is deemed as a prerequisite for its broad applications; however, there is a contradiction from experiments as to whether boron atoms in borophenes are active or...

The successive discoveries of the cage-like D2d B40−/0 and C3/C2 B39− mark the onset of borospherene chemistry. Based on extensive global minimum searches and first-principles theory calculations, we predict herein the possible existence of the axially chiral cage-like C2 B38+ (1/1′) and C2 B382+ (3/3′) which are novel aromatic members of the borospherene family featuring a B21 boron triple-chain on the waist and four B6 hexagonal holes on the cage surface. Detailed bonding analyses show that the B38+ (1) and B382+ (3) possess 12 and 11 delocalized π bonds over a σ-skeleton, respectively, following the universal bonding pattern of σ + π double delocalization of the borospherene family. Extensive molecular dynamics simulations indicate that both B38+ (1) and B382+ (3) are dynamically stable at 700 K. The IR, Raman, and UV–vis spectra of these cluster cations are computationally simulated to facilitate their future spectral characterizations.

Coking on Ni surfaces limits the direct application of methane-based fuels in SOFCs with Ni-cermet anodes. Loading an anodic catalytic layer with a high catalytic activity for CH4 conversion can effectively protect the Ni-based anode from coking and increase the cell durability. In this work, a Ni–Fe alloy composite catalyst was prepared by reducing perovskite La0.7Sr0.3Fe0.8Ni0.2O3-δ (LSFN) and then evaluating its catalytic activity in the partial oxidation of CH4. The catalyst was applied on a conventional Ni–8 mol.% Y-stabilized ZrO2 (YSZ) anode for methane SOFCs using two methane-containing fuels (97% CH4–3% H2O and 30% CH4–70% air). The catalyst-modified cells showed much higher performances and durability than the conventional cell using a Ni–YSZ anode, indicating the potential application for direct-methane SOFCs.

This paper reports a way to utilize low-concentration coal-bed gas(LC-CBG) to generate power using SOFC technology. Ni–BaO–CeO2@SiO2 (@NBC) porous nanoparticles with a core-shell structure were synthesized and applied as a protective layer on an anode consisting of Ni–yttria stabilized zirconia (Ni–YSZ). Catalytic activity of @NBC relative to methane partial oxidation was evaluated. Electrochemical performance and durability of the @NBC-modified cells (@NBC//Ni–YSZ) were tested fed with simulated LC-CBG (30% CH4–70% air). A conventional cell without a protective layer (Ni–YSZ) and a bare NBC-modified cell (NBC//Ni–YSZ) were used for a comparison. The pre- and post-mortem microstructures of cells were analyzed. Influence of porosity of the anode layer on polarization resistance was also investigated. The loading mode of catalysts was discussed as well. Using simulated LC-CBG as a fuel, peak power density of @NBC//Ni–YSZ showed 50% increase at 800 °C comparing with Ni–YSZ at the same conditions. The aging test in galvano-static mode demonstrated good durability of @NBC//Ni–YSZ lasting for over 160 h when exposed to LC-CBG. For comparison, NBC//Ni–YSZ showed rapid voltage drop after 60 h. Voltage of the Ni–YSZ dropped after 10 h. No coking was observed on the @NBC//Ni–YSZ anode surface after the durability tests.

Transition-metal doping induces dramatic structural changes and leads to earlier planar → tubular → spherical → core–shell-like structural transitions in boron clusters. Inspired by the newly discovered spherical trihedral metallo-borospherene D3h La3&B18− (1) (Chen, et al., Nat. Commun., 2020, 11, 2766) and based on extensive first-principles theory calculations, we predict herein the first and smallest core–shell-like metallo-borospherenes C2v La3&[B2@B17]− (2) and D3h La3&[B2@B18]− (3) which contain a transition-metal-like B2 core at the cage center with unique donor–acceptor duality in La3&Bn− spherical trihedral shells (n = 17, 18). Detailed energy decomposition and bonding analyses indicate that the B2 core in these novel complexes serves as a π-donor in the equatorial direction mainly to coordinate three La atoms on the waist and a π/σ-acceptor in the axial direction mainly coordinated by two B6 triangles on the top and bottom. These highly stable core–shell complexes appear to be spherically aromatic in nature in bonding patterns. The IR, Raman, and photoelectron spectra of 2 and 3 are computationally simulated to facilitate their spectroscopic characterizations.

Since the discovery of the cage-like borospherenes D2d B40−/0 and the first axially chiral borospherenes C3/C2 B39−, a series of fullerene-like boron clusters in different charge states have been reported in theory. Based on extensive global minimum searches and first-principles theory calculations, we present herein two new axially chiral members C2 B31+ (I) and C2 B32 (VI) to the borospherene family. B31+ (I) features two equivalent heptagons on the top and one octagon at the bottom on the cage surface, while B32 (VI) possesses two equivalent heptagons on top and two equivalent heptagons at the bottom. Detailed bonding analyses show that both sea-shell-like B31+ (I) and B32 (VI) follow the universal σ + π double delocalization bonding pattern of the borospherene family, with ten delocalized π bonds over a σ skeleton, rendering spherical aromaticity to the systems. Extensive molecular dynamics simulations show that these novel borospherenes are kinetically stable below 1000 K. The IR, Raman, and UV-vis spectra of B31+ (I) and B32 (VI) are computationally simulated to facilitate their future experimental characterizations.

SrCo0.8Fe0.2O3−δ (SCF) exhibits high ionic–electronic conductivity. However, its instability in the presence of CO2 restricts its application in electrochemical devices. In this study, 5 mol% zirconium was introduced into SCF to improve its structural stability and CO2 tolerance. SrCo0.8Fe0.15Zr0.05O3−δ (SCFZ) showed metallic electrical conductivity above 500 °C. Furthermore, X-ray diffraction and CO2-temperature programmed desorption experiments indicated that SCFZ possessed adequate structural stability and CO2 tolerance. The oxygen reduction activity and CO2 tolerance were studied using a symmetrical cell, SCFZ|BaZr0.1Ce0.7Y0.1Yb0.1O3−δ (BZCYYb)|SCFZ. The electrochemical performances of the SCFZ material as a cathode were investigated systematically for proton-conducting solid oxide fuel cells (H+-SOFCs) with a configuration of NiO–BZCYYb|BZCYYb|SCFZ–BZCYYb. The output of 712 mW cm−2 at 700 °C and a durability test of over 300 h indicated that SCFZ had significant structural stability and CO2-tolerance.