Os Atoms Research Articles

Photo-assisted highly efficient electrocatalytic N2 fixation on nonmetal-metal dual atom catalysts through the reversable evolution of active center

The electrocatalytic reduction naturally abundant dinitrogen (N2) to ammonia (NH3) offers a promising alternative to the harsh Haber–Bosch process. However, developing catalysts for high-performance electrocatalytic N2 reduction reaction (NRR) remains a significant challenge. In this study, density functional theory (DFT) calculations were employed to investigate boron-transition metal atom pairs (B–TM) supported on graphitic carbon nitride (g-C6N6) as dual-atom catalysts for photo-assisted electrocatalysis of NRR. It was demonstrated that B–TM atom pair can be successfully embedded on g-C6N6. Among the considered B–TM@g-C6N6 catalysts, B–Os@g-C6N6 exhibits exceptional catalytic activity for NRR via a consecutive mechanism, with the lowest overpotential of 0.21 V, outperforming the efficiency of widely used noble catalysts. Notably, both B and Os atoms directly participate in N2 activation through σ-donation and π*-backdonation mechanism. Furthermore, the adsorption of intermediates can induce the reversable evolution of the active center, accelerating the NRR. Therefore, these novel characteristics endow B–Os dual atom catalyst with excellent NRR performance. Importantly, B–Os@g-C6N6 also shows suitable band edges and high capability of visible-light absorption, which can assist N2 conversion under visible-light irradiation. This work offers new insights and ideas for designing nonmetal-metal atom pair as dual atom catalyst for the photo-assisted electrocatalytic reduction of N2 to NH3.

Enhanced VOCs adsorption on Group VIII transition metal-doped MoS2: A DFT study

Volatile organic compounds (VOCs) represent a significant category of toxic and harmful air pollutants. Among the various abatement techniques available for VOCs, adsorption technology is widely recognized as a cost-effective solution. In this study, density functional theory (DFT) was employed to calculate and compare the adsorption capacities of six typical VOCs on pristine MoS2 and MoS2 modified with Group VIII (MVIII) transition metals atoms. It is found that MVIII-MoS2 monolayer demonstratesa significant enhancement in adsorption capabilities for VOCsrelative to pristine MoS2. Among these Group VIII transition metals atoms, Fe, Ru and Os atoms exhibited the most significant VOCs adsorption enhancement, with Fe atoms demonstrating a particularly pronounced effect. This suggests a synergistic interaction between the metal dopants and the substrate. Density of states (DOS) and charge density difference analyses provided further insights into the mechanisms underlying improved adsorption capability. Interestingly, the introduction of MVIII atoms results in the emergence of a novel state density within the surface state of MoS2, thereby facilitating enhanced electron transfer between VOCs and the substrate. Charge density difference calculations further corroborated these findings, with certain configurations exhibiting significant electron cloud overlap. Such modification leads to more active electron transfer, thereby increasing the substrate’s affinity for VOC molecules and consequently improving the adsorption efficiency. The findings not only enhance the comprehension of VOC adsorption mechanisms on MoS2 but also underscore the potential of metal-doped two-dimensional materials for environmental applications.

First principles insights into the electronic and magnetic properties of [formula omitted] doped with VIII-group transition metal single atom

Inspired by the unprecedented surface chemical reaction activity of single-atom catalysts (SAC), this research presents a theoretical study on the doping of SnO2(110) surface with transition metal group VIII atoms (Fe, Co, Ni, Ru, Rh, Pd, Os, Ir, Pt). Using density functional theory (DFT), the formation energy, electronic structure, charge transfer and magnetic moments of the SnO2(110) system before and after doping were investigated. The formation energies of the different doped systems vary depending on the doping position. The doping of transition metal (TM) atoms can induce produces both charge transfer and magnetic moment. The charge transfer is largest in the Pd-doped system, with + 0.68 e at the position of the penta-coordinated Sn atom (Sn5c position) and + 0.67 e at the position of the hexa-coordinated Sn atom (Sn6c position), while the Co-doped system exhibits the smallest charge transfer of + 0.19 e (Sn6c position). Fe, Co, Ni, Ru and Os atoms introduce magnetic moments, with the Fe-doped system (Sn5c position) having the highest magnetic moments of 2.91 μB. In the SnO2(110) surface system doped with TM atoms, there are varying degrees of orbital overlap between the TM atoms and their surrounding O atoms. This theoretical work provides valuable insights into the physical properties of metal oxide based single-atom catalysts.

Structural, magnetic, elastic, and thermoelectric properties of Ba2InOsO6 double perovskite in the cubic phase: A DFT + U study with spin-orbit-coupling

In this study, we comprehensively investigate the structural, electronic, magnetic, elastic, and thermal properties of the double perovskite Ba2InOsO6 using density functional theory (DFT). Our results show that the ferromagnetic phase is the most stable, with the net magnetic moment primarily arising from the Os atom. The half-metallic behavior exhibited by Ba2InOsO6, characterized by a band gap of 3.62 eV in the TB-mBJ + U approximation, decreases upon the inclusion of spin–orbit coupling (SOC). This half-metallic property, coupled with the stability of the ferromagnetic phase, makes Ba2InOsO6 particularly suitable for spintronic applications, as it can facilitate efficient spin injection and transport. Elasticity analysis indicates moderate brittleness, while thermoelectric properties, calculated using the Boltzmann transport model, reveal n-type conductivity and notable thermopower, suggesting potential for thermoelectric applications. This work provides a solid foundation for future experimental studies and potential applications in advanced technologies.

Noble metal-modified copper surfaces for alkaline condition hydrogen evolution reaction

Cu-based materials would be attractive candidates for cost-effective alkaline hydrogen evolution reaction (HER) electrocatalysts due to high abundance, excellent conductivity, and excellent stability in alkaline environments, if not for the inherent inertness of Cu in HER. This inertness has led to a relative lack of research on Cu-based HER catalysts in both experimental and theoretical domains. Here, We report engineered Cu(111) surfaces that can significantly improve the poor activity of H2O dissociation on pure Cu(111) surface. We do this by introducing noble metal atoms (M = Ru, Rh, Pd, Ag, Os, Ir, Pt) through surface doping. These modified surfaces exhibit excellent thermodynamic and electrochemical stability, with the exception of Cu(111)-Ag. Notably, the H2O dissociation energy barrier on Cu(111)-Os (Eb) is only 0.74 eV, which is much smaller than that (1.31 eV) of pure Cu(111), and is even lower than that of Pt (Eb = 0.92 eV), which is commercially used for electrodes. The low Eb and resulting expected excellent performance of Cu(111)-Os for water splitting is related to the particular local electronic properties of doped Os atoms, specifically the electronic structure of the Os d-orbitals, which have a d-band center near Fermi level (EF) and a high density of states around EF, including just above EF. These results are expected to stimulate the investigation of surface alloyed Cu, leading to a new direction for the design of high-performance and low-cost electrocatalysts.

Non-trivial topological surface states regulation of 1 T-OsCoTe2 enables selective C―C coupling for highly efficient photochemical CO2 reduction toward C2+ hydrocarbons

Despite ongoing research, the rational design of non-trivial topological semimetal surface states for the selective photocatalytic CO2 conversion into valuable products remains full of challenges. Herein, we present the synthesis of lattice-matched 1 T-OsCoTe2 for the photoreduction upgrading of CO2 to tri-carbon (C3) alkane (propane, C3H8) by the integration of experimental work and theory prediction/calculation. Experimental studies suggested a high electron-based selectivity of 71.2 % for C3H8 and an internal quantum efficiency of 54.6 % at 380 nm. In-situ X-ray photoelectron spectroscopy and X-ray absorption fine structure spectroscopy demonstrated that Co and Os atoms coordinated with Te atoms enable an efficient Os―Te―Co electron transfer to activate the generation of *CH3, *CHOCO and *CH2OCOCO. Density functional theory calculations further confirmed Os―Te―Co electron bridging on the improved CO2 conversion kinetics. To our knowledge, this is the first report suggesting the role of Os atoms in accelerating the photocatalytic CO2 conversion activity of the topological semimetal 1 T-OsCoTe2.

Evidence for the formation of (NN)xMN(M=Os and Ru) (x=1–3) complexes

MN and their N2 complexes (NN)MN, (NN)2MN, and (NN)3MN (M=Os and Ru) were obtained in the reaction of laser-ablated transition metal Os and Ru atoms with nitrogen in excess solid argon at 4 K through matrix isolation infrared spectroscopy and quantum chemical calculations. The maximum coordinated N2 number is got according to the energy surface. With the increase of coordinated number, the M-N bond length increase in accordance with the red shift of M-N stretching mode from 1130.2 cm−1 to 1052.1 cm−1 for OsN series and from 1119.1 cm−1 to 984.1 cm−1 for RuN series. In addition, a new product (NN)2NOsOsN(NN)2 was discovered in the reaction of laser-ablated Os with N2 in N2 matrix, which could be regarded as NOsOsN coordinated by four N2 molecules. The reason that growth of M-N bond length in (NN)xMN with the N2 coordination was explained in detail, which was mainly caused by relativistic effect.

Rule breaker boron clusters: a new class of hypoelectronic osmaborane clusters [(Cp*Os)2BnHn] (n = 6-10).

Since the pioneering electron counting rule for borane clusters was proposed by Wade, the structures and bonding of boron clusters and their derivatives have been elegantly rationalised. However, this rule and its modified versions faced problems explaining the electronic structures of less spherical deltahedra, unlike the core geometries of borate dianions [BnHn]2- (n = 6-12). Herein, we report the isolation of a series of osmaborane clusters [(Cp*Os)2BnHn], 1-5, (n = 6-10) by the thermolysis of an in situ generated intermediate, obtained from the rapid condensation of [Cp*OsBr2]2 and [LiBH4·THF], with [BH3·THF] or [BH3·SMe2]. Interestingly, all these clusters show unusual less spherical deltahedral shapes that can be generated from canonical [BnHn]2- (n = 8-12) shapes by doing diamond-square-diamond (DSD) rearrangements. The DSD rearrangements led to the generation of higher degree vertices, which are occupied by Os atoms and also generated Os-Os bonds in these clusters. Theoretical calculations revealed that these Cp*Os⋯OsCp* interactions in clusters 1-5 played a crucial role in their structural shape and electron count. These less spherical deltahedral clusters are rare, and most significantly, clusters 1-5 with (n-1) skeleton electron pairs (SEPs) do not follow Wade-Mingos electron counting rules and can be classified as hypoelectronic closo clusters.

Unraveling the enigma of Craig-type Möbius-aromatic osmium compounds.

Nuclear magnetic resonance (NMR) chemical shifts and the magnetically induced current density (MICD) susceptibility of four osmium containing molecules have been calculated at the density functional theory (DFT) level using three relativistic levels of theory. The calculations were performed at the quasi-relativistic level using an effective core potential (ECP) for Os, at the all-electron scalar exact two-component (X2C) relativistic level, and at the relativistic X2C level including spin-orbit coupling (SO-X2C). In earlier studies, the osmapentalene (1) and the osmapentalynes (2 and 3) were considered Craig-type Möbius aromatic and it was suggested that the analogous osmium compound (4) is Craig-type Möbius antiaromatic. Here, the ring-current strengths were obtained with the gauge including magnetically induced currents (GIMIC) method by integrating the MICD susceptibility passing through planes that intersect chemical bonds and by line integration of the induced magnetic field using Ampère-Maxwell's law. The ring-current calculations suggest that 1, 2 and 3 are weakly aromatic and that 4 is nonaromatic. The accuracy of the MICD susceptibility was assessed by comparing calculated NMR chemical shifts to available experimental data. Visualization of the MICD susceptibility shows that the ring current does not pass from one side of the molecular plane to the other, which means that the MICD susceptibility of the studied molecules does not exhibit any Möbius topology as one would expect for Craig-type Möbius aromatic and for Craig-type Möbius antiaromatic molecules. Thus, molecules 1-3 are not Craig-type Möbius aromatic and molecule 4 is not Craig-type Möbius antiaromatic as previously suggested. Calculations of the 1H NMR and 13C NMR chemical shifts of atoms near the Os atom show the importance of including spin-orbit effects. Overall, our study revisits the understanding of the aromaticity of organometallic molecules containing transition metals.

Strain and stacking induced topological phase transition in bipolar ferromagnetic semiconductor OsClBr

The combination of valleytronics and topology has great potential significance in condensed matter and material physics. Here, based on first-principles calculations, we predict a dipolar ferromagnetic semiconductor OsClBr. Benefiting from strong spin–orbit coupling and the intrinsic exchange interaction of localized d electrons, spontaneous valley polarization occurs. In addition, the tensile strain can induce topological phase transitions between ferrovalley, half-valley-metal, and valley-polarization quantum anomalous Hall (VQAH) phases, which can be attributed to the band inversion between dz2 and dxy/dx2−y2 orbitals of Os atom. Moreover, stacking-dependent topological phase transitions can be found in bilayer OsClBr, and the robustness of VQAH phase in b − 1 configuration under a wide strain range has been proved, which is greatly beneficial for the regulation of quantum states. Our work provides a potential opportunity for the preparation and application of low-power consumption electronics devices.

Kagome-like BiP3 Monolayer: An Emerging Quasi-Direct Auxetic Semiconductor Coupled with High Anisotropic Mobility toward Visible-Light-Driven Photoelectrocatalytic pH-Robust Overall Water-Splitting.

Two-dimensional (2D) Janus materials exhibit an outstanding potential that can meet the rigorous requirements of photocatalytic water splitting resulting from their unique atomic arrangement. However, these materials are quite scarce. Through ab initio density functional theory calculations, we introduce a kagome topology into the honeycomb lattice of blue phosphorene using phosphorus and bismuth atoms to build a hybrid honeycomb-like kagome lattice, realized by a hitherto unknown kagome-like Janus-like BiP3 monolayer with robust stability. Excitingly, the out-of-plane asymmetry benefiting from kagome and honeycomb topologies gives rise to a significantly negative out-of-plane Poisson's ratio and an obvious built-in electric field pointing from the sublayer of the P atom to the sublayer of the Bi atom. In conjunction with the investigations that encompass semiconducting properties, such as a quasi-direct gap, suitable band-edge positions, effective visible-light absorption, and high carrier mobility, the BiP3 monolayer achieves overall water splitting at pH 0-14 regardless of strain. Moreover, this intrinsic electric field provides a sufficient photogenerated carrier driving force for water splitting. The bare BiP3 comprises P and Bi atoms that function as catalysts for the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) active sites, respectively. Upon exposure to light, the reaction of water into H2 and O2 can be observed across a pH range of 0-14. Meanwhile, by designing a transition-metal single-atom catalyst (TM@BiP3), our investigations have shown that embedding a single TM on BiP3 is a feasible route to improving the HER/OER activity by reducing the overpotentials to -0.039 and 0.58 eV for Mo and Os atoms, respectively. In this case, the positive value of the external potential acts as a sufficient OER driving force, i.e., in the light environment, the Os@BiP3 system can promote water molecules spontaneously oxidized into O2 at pH 0-14.

Tuning Active Metal Atomic Spacing by Filling of Light Atoms and Resulting Reversed Hydrogen Adsorption-Distance Relationship for Efficient Catalysis

HighlightsDensity functional theory calculations indicates that interstitial B atoms can tune the atomic spacing of host metal Os and achieve a reversal hydrogen adsorption-distance relationship.The structure–activity relationship between the spacing of active Os atoms and catalytic activity is established.Prepared OsB2 with increasing dOs-Os of 2.96 Å presents the optimal hydrogen evolution reaction activity (8 mV @ 10 mA cm−2) and robust stability in alkaline media.

Electronic-correlation induced sign-reversible Berry phase and quantum anomalous valley Hall effects in Janus monolayer OsClBr.

Topological phase transition can be induced by electronic correlation effects combined with spin-orbit coupling (SOC). Here, based on the first-principles calculations +U approach, the influence of electronic correlation effects and SOC on topological and electronic properties of the Janus monolayer OsClBr is investigated. With intrinsic out-of-plane (OOP) magnetic anisotropy, the Janus monolayer OsClBr exhibits a sequence of states, namely, the ferrovalley (FV) to half-valley-metal (HVM) to quantum anomalous valley Hall effect (QAVHE) to HVM to FV states with increasing U values. The QAVHE is characterized by a chiral edge state linking the conduction and valence bands with a Chern number C = 1, which is closely associated with the band inversion between dx2-y2/dxy and dz2 orbitals, and sign-reversible Berry curvature. The section with larger U values (2.31-2.35 eV) is very essential for determining the new HVM and QAVHE states, and also proves that a strong electron correlation effect exists in the interior of the Janus monolayer OsClBr. When taking into consideration a representative U value (U = 2.5 eV), a valley polarization value of 157 meV can be observed, which can be switched by reversing the magnetization direction of Os atoms. It is noteworthy that the Curie temperature (TC) strongly depends on the electronic correlation effects. Our work provides a comprehensive discussion on the electronic and topological properties of the Janus monolayer OsClBr, and demonstrates that the electronic correlation effects combined with SOC can drive the emergence of QAVHE, which will open up new opportunities for valleytronic, spintronic, and topological nanoelectronic applications.

Understanding the acceleration effect of manganese and cerium doping on the hydration of CaO in CaO/Ca(OH)2 heat storage by density function theory

CaO/Ca(OH)2 heat storage system is one of the most promising candidates for large-scale thermochemical heat storage at temperature of 300–600 °C. In this work, the CaO/Ca(OH)2 heat storage performances of the Ce- and Mn-doped CaO were investigated and the mechanisms of promoting hydration by Ce and Mn doping were determined via density functional theory (DFT) calculations. The Mn-doped CaO exhibits the higher hydration conversion than CaO and Ce-doped CaO. The structural parameters, partial density of states, electron differential densities and energy barriers during hydration stage on the CaO, Ce- and Mn-doped CaO surfaces were compared to clarify the effects of Ce and Mn on hydration of CaO. The results show the detailed hydration reaction pathways on the CaO, Ce- and Mn-doped CaO surfaces. During the H2O adsorption stage, H2O on the Ce-doped CaO surface approaches the Ca atom first, while H2O on the Mn-doped CaO surface approaches the Os atom first. The adsorption energy for Ce- and Mn-doped CaO are −1.612 and −0.896 eV, respectively, which are higher than that for CaO. The doping of Ce and Mn accelerates the H2O adsorption on the CaO surface. The Mn doping causes the 84.3 % reduction in the energy barrier for hydration of CaO and the reduction by Mn doping is larger than that by Ce doping. Thus, Mn-doped CaO exhibits the higher hydration reactivity and hydration conversion than CaO and Ce-doped CaO. The DFT calculations determined the promotion mechanism of Ce and Mn doping on the hydration of CaO in CaO/Ca(OH)2 heat storage.

High-throughput identification of highly active and selective single-atom catalysts for electrochemical ammonia synthesis through nitrate reduction

The highly selective and active nitrate-to-ammonia electrochemical conversion (NO3 reduction reaction [NO3RR]) can be an appealing and supplementary alternative to the Haber-Bosch process. It also opens up a new idea for addressing nitrate pollution. Previous study demonstrated that FeN4 single-atom catalyst (SAC) indicates excellent NO3RR performance. Nonetheless, the mechanism that triggers the electrocatalytic NO3RR remains unclear. The feasibility of NO3RR over various SACs is verified in this study via high-throughput density functional theory calculations with the single transition metal (TM) atom coordinated with four nitrogen atoms supported on graphene as the example. We conducted a comprehensive screening of TM SAC candidates for stability, NO3− adsorption strength, catalytic activity, and selectivity. Results reveal that the most promising candidate among the 23 TM SACs is Os SAC with a low limiting potential of − 0.42 V. Os SAC is better than Fe SAC with a limiting potential of −0.53 V because of the strong interaction between the oxygen of NO3− species and Os atom. The origin of high NO3RR activity of Os SAC is explained by its inner electronic structure of the strong hybridization of the Os atom and NO3− caused by the increasing charge transfer from TM atom to NO3−, leading to the suitable NO3− adsorption. This research provides a fundamental insight of discovering novel NO3RR catalysts and may provide a motivating drive for the creation of effective ammonia electrocatalysts for further experimental investigation.

Rotationally ordered ammonium cations in the crystal structure of (NH4)2OsBr6

AbstractRotational disorder is a common phenomenon in ammonium salts. The localization of hydrogen atoms and thus the distinction between rotationally ordered and disordered ammonium atoms by laboratory based X‐ray powder diffraction (XRPD) is a challenge, especially for compounds containing heavy atoms. For ammonium hexabromido osmate(IV), (NH4)2OsBr6, the analysis of XRPD data reveals a slight preference for a structure model with fully ordered ammonium cations ((ND4)2PdCl6 type (filled K2PtCl6 type), Fm m, a=1037.954(9) pm at 293(1) K, Br atoms on 24e with x(Br)=0.2385(1), H atoms on 32f with x(H)=0.191(2), Os atoms on 4a, N atoms on 8c). Interatomic distances (d(Os−Br): 6*247.6(1) pm, d(N−H): 4*106(2) pm, d(H−H): 3*173(3) pm) are consistent with those in comparable compounds, e. g. NH4Br and K2OsBr6. X‐ray diffraction (293 K≤T≤673 K) and thermal analysis (113 K≤T≤673 K) did not show any phase transition or any signs of disorder. The lattice parameters develop nearly linearly as described by the polynomial fit a=1024.38(16) pm+0.0410(7) T pm/K+8.8(7)×10−6 T2 pm/K2 for 313 K≤T≤653 K. (NH4)2OsBr6 shows beginning sublimation at 680 K. We therefore conclude that (NH4)2OsBr6 adopts the cubic (ND4)2PdCl6 type with fully ordered NH4+ cations from room temperature up to the temperature of its decomposition.

Strongly anisotropic electronic and magnetic structures in oxide dichlorides RuOCl2 and OsOCl2

Here, using density functional theory and density matrix renormalization group methods, we investigate the electronic and magnetic properties of RuOCl$_2$ and OsOCl$_2$ with $d^4$ electronic configurations. Different from a previous study using VOI$_2$ with $d^1$ configuration, these systems with $4d^4$ or $5d^4$ do not exhibit a ferroelectric instability along the $a$-axis. Due to the fully-occupied $d_{xy}$ orbital in RuOCl$_2$ and OsOCl$_2$, the Peierls instability distortion disappears along the $b$-axis, leading to an undistorted I${\rm mmm}$ phase (No. 71). Furthermore, we observe strongly anisotropic electronic and magnetic structures along the $a$-axis. The large crystal-field splitting energy (between $d_{xz/yz}$ and $d_{xy}$ orbitals) and large hopping between nearest-neighbor Ru and Os atoms suppresses the spin-orbital effect in $M$OCl$_2$ ($M$ = Ru or Os) with electronic density $n = 4$, resulting in a spin-1 system instead of a $J = 0$ singlet ground state. Moreover, we find staggered antiferromagnetic order with $\pi$ wavevector along the $M$-O chain direction ($a$-axis) while the magnetic coupling along the $b$-axis is weak. Based on Wannier functions from first-principles calculations, we calculated the relevant hopping amplitudes and crystal-field splitting energies of the $t_{2g}$ orbitals for the Os atoms to construct a multi-orbital Hubbard model for the $M$-O chains. Staggered AFM with $\uparrow$-$\downarrow$-$\uparrow$-$\downarrow$ spin structure dominates in our DMRG calculations, in agreement with DFT calculations.

Unraveling the adsorption behaviors of uranium and thorium on the hydroxylated titanium carbide MXene

Hydroxylated titanium carbide Ti3C2(OH)2, a representative of MXenes, is employed to investigate adsorption behaviors for uranium and thorium using density functional theory based simulation methods. The structural analysis of the complexes compares very well to existing computational and experimental literatures. A closer look at the adsorption configurations and energies indicates that the main adsorption sites are deprotonated Os atoms of the OH groups terminated on the Ti3C2(OH)2 MXene surface. The most stable models for U(VI) and Th(IV) adsorbed on the Ti3C2(OH)2 MXene in the gas phase are bidentate and tridentate configurations, respectively. The adsorption ability of Th(IV) on the Ti3C2(OH)2 MXene is stronger than that of U(VI). More importantly, the aqueous solution has a remarkable effect on the coordinated environment of uranyl and Th4+ ions in the binding configurations. Uranyl and Th4+ ions adsorbed on the Ti3C2(OH)2 MXene in the aqueous environment form pentavalent coordinated structures. Extra OH– ligands from water molecules are found to interact with U and Th atoms compared with the adsorption configurations in the gas phase. Moreover, U-Oax double bonds in the uranyl break to form U-OH bonds in the adsorption model. For all the stable adsorption configurations, the coordinating interaction is the dominant factor, and Th-Os bonds present more covalent nature than U-Os bonds due to the larger charge transfers between Th and Os atoms. This work gives supplement to the experimental observations and will provide deeper insights into the physical chemistry behind the removal of uranium and thorium by using MXenes.

High-Throughput computational screening of Single-atom embedded in defective BN nanotube for electrocatalytic nitrogen fixation

The boron nitride nanotubes (BNNTs) have been widely used in various energy applications such as hydrogen storage, gas sensor, carbon dioxide reduction reaction, and so on. Herein, the potential application of BNNT-based catalysts was explored in electrocatalytic nitrogen reduction reaction (eNRR) by density functional theory (DFT) computations. A series of single metal/non-metal atoms (18 transition metals (3d ∼ 5d) and 6 non-metals (B, C, N, Si, P, and As)) supported on the defective BNNT were investigated. Among them, Os-doped (Os@BNNT) single-atom catalyst (SAC) can significantly promote the NRR process, and possess a rather low overpotential (0.31 V), as well as high selectivity over HER competition. The confined Os atom not only serves as an electron donor to supply electrons for NRR, but also acts as a channel for interfacial charge transfer between substrate and NRR intermediates. Moreover, the curved surface of BNNT can decrease the barrier for protonating *NH2 to·NH3. The synergistic collaboration of single-atom Os catalyst and curved surface of BNNT facilitates the NRR process. Our findings open up a new avenue for designing novel nanotube-based materials as eNRR electrocatalysts.

NO adsorption on the Os, Ir, and Pt embedded tri-s-triazine based graphitic carbon nitride: A DFT study

In this work, we have studied the adsorption performance of NO gas in the pristine and Os, Ir and Pt embedded g-C3N4 using the density functional theory calculations. It is found that the hexagonal cavity is the most stable site for the embedding of Os, Ir, and Pt on the g-C3N4. The obtained outcomes indicate that NO is physisorbed on pristine g-C3N4 whereas chemisorbed on the Os, Ir, and Pt embedded g-C3N4. The bandgap energy considerably decreases after embedding Os, Ir, and Pt atoms and NO adsorption. Partial density of states plots indicates that embedded metals are a bridge to enhance the hybridization between NO and the g-C3N4. The repositioning of HOMO and LUMO is noticed in the Os, Ir, and Pt embedded g-C3N4. Furthermore, it is observed that Os, Ir, and Pt embedded g-C3N4 are magnetic with total magnetic moments of 3.4037, 2.0476, and 1.6641 μβ correspondingly, which undergoes a significant change after NO adsorption. The Bader charge analysis indicates the acceptor nature of the NO gas molecule further validated the charge density difference calculations. Our calculations reveal that Ir embedded g-C3N4 can be considered an outstanding candidate for sensing NO gas and its elimination from the atmosphere.