O2 Molecules Research Articles

Plasma atomic layer etching of ruthenium by oxygen adsorption-removal cyclic process

Ruthenium (Ru) is a next-generation metal interconnect material, and the demand for precise etching is on the rise. This study explores anisotropic atomic layer etching (ALE) of Ru, utilizing various oxygen adsorption methods (O radical, oxygen plasma, or O2 molecule) and two types of plasma sources: inductively coupled plasma (ICP) and ion beam source. Through ICP ALE, an etch per cycle (EPC) of ∼ 1.5 Å/cycle was achieved using oxygen plasma for adsorption. For ion beam ALE, EPC values of ∼ 0.8 Å/cycle were obtained using oxygen radical, and ∼ 0.4 Å/cycle through physisorption using oxygen molecule without plasma generation. The higher EPC with the ICP ALE was attributed to spontaneous etching during oxygen adsorption during the oxygen plasma generation. Conversely, the lower EPC with ion beam ALE during oxygen adsorption using O2 molecule without plasma generation resulted from nonuniform oxidation of Ru during the adsorption step. Among the three ALE methods, optimal Ru ALE with 100 % ALE synergy was achieved with ion beam ALE, likely due to the absence of ion bombardment during oxygen adsorption and the precise Ar+ ion energy for removing RuOx formed on the surface.

Dynamics of the Decomposition of Gas Molecules Containing Sulfur and Nitrogen from Char-S and Char-N Structures in Combustion and Pyrolysis Reactions

ABSTRACT Combustion states of char-S (C14H16O4S) and char-N (C18H19NO3) sub function molecules in a limited number of oxygen environments and pyrolysis states at high temperatures were examined quantum mechanically. In the study, the formation of all gases, with or without carbon, were determined. All the dynamics in which the O2 molecule could be effective in the combustion mechanism and all the elements that could affect the decomposition in the pyrolysis event were determined. The dynamics of the formation and disappearance of the highly stable CO molecule and CH2O (formaldehyde) molecules were shown in detail. It has been shown that the CO molecule is a catalysis that can bond with hydrocarbon groups and decompose them into small hydrocarbon groups at high temperature. In this study, it was shown that high temperature-dependent vibration and rotational energies, CO molecule and H-atom transfers play a role in the decomposition in the pyrolysis system, and the aromatic carbon ring group is the last particle group to decompose. In addition, the formation and dissociation dynamics of sulfoxylic acid, thioformic acid, hydrogen sulfide molecules originating from the Char-S system, as well as the formation conditions of hydrogen cyanide and pyridinyl molecules originating from the Char-N system, were determined. The study also showed that since the N-atom is located in the aromatic carbon ring, it makes the emergence of the nitrous oxide molecule difficult in pyrolysis systems.

Hollow porous organic framework nanotube for efficient photocatalytic H2O2 generation by promoting H2O oxidation

The hydrogen peroxide (H2O2) generation by photocatalytic O2 reduction coupling H2O oxidation is a promising alternative to the traditional anthraquinone method. However, the low mass transfer and weak water oxidation are still the major responsible for the low efficiency of photocatalytic H2O2 production. Herein, we present a porous organic framework (BPTEE-POF) with hollow nanotube structure containing 2,2′-bipyridine active center of H2O oxidation, which was synthesized by template-free Sonogashira cross-coupling reaction of 5,5′-dibromo-2,2′-bipyridine (BP) and 1,1,2,2-tetrakis(4-ethynylphenyl)ethene (TEE). The 2,2′-bipyridine moieties can effectively weaken HO bond and facilitate H2O oxidation to generate O2 and H+, which can be subsequently employed as reactants for non-sacrificial H2O2 production. Meanwhile, the throughout hollow structure of BPTEE-POF is conducive to mass transfer/diffusion of substrate and product by siphoning, which promotes O2 and H2O molecules to contact with catalytic active sites and causes the quick dissociation of H2O2 from active sites, thereby boosting the overall reaction kinetic and efficiency.

Efficient photocatalytic activity by constructing double anion defects: synergistic and process mechanism

An S-Ov co-modified double defects photocatalyst (S10 %-ZnOov) for efficient degradation of pollutants in the water environment was fabricated by introducing S and Ov into ZnO through simple hydrothermal procedures. The prepared S10 %-ZnOov exhibited enhanced photoactivity (major pollutants degradation within 60 min) and double defects synergistic co-promotion in the photocatalytic system. Experiments, characterization, and DFT calculations confirmed that the introduced S-Ov double defects not only provided stable and efficient electronic channels for electron transfer on the material surface (promoting the separation and transfer process of charges), but also provided abundant active sites (facilitated adsorption and oxide process of H2O and O2 molecules) for the surface catalytic process, which achieved the enhancement of photocatalytic performance and promoted the generation of ROS (H2O2, ·OH and O2·-). This study revealed the synergistic mechanism and catalytic properties of the double defects, providing a new idea for the development of highly active photocatalysts for environmental remediation.

The intense charge migration and efficient photocatalytic NO removal of the S-scheme heterojunction composites Bi7O9I3-BiOBr

For purpose of efficient photocatalytic removal of NO molecules, both components of bismuth-rich Bi7O9I3 and BiOBr were typically selected to create binary heterojunction composites Bi7O9I3-BiOBr (BI-BBX) through a facile in-situ synthetic protocol. These composites underwent thorough characterization using a range of analytical methods and were subjected to photocatalytic removal of NO at ppb level under visible light for the first time. These produced composites showed enhanced photocatalytic behavior and the best candidate BI-BB0.2 demonstrated the highest removal efficiency among all tested samples. Density-functional theory (DFT) calculations revealed the intense charge migration at the interface. In addition, the composites surface exhibited a propensity to adsorb and activate O2, H2O, and NO molecules, thus promoting the catalytic conversion of NO to NO2– and further NO3– species. Entrapping experiments and electron spin resonance (ESR) results demonstrated the increased generation of oxygen-containing species O2–, 1O2, and ·OH, which was attributed to the rational creation of heterojunctions with similar crystal structures and efficient migration and separation of generated charge carriers in an S-scheme model. This study provides insight into the design and development of Bi7O9I3-based composites for effective dislodge of NO upon the visible-light irradiation.

Pinning-effect single-atom NiCo alloy embedded graphene-aerogel in electro-fenton process for rapid degradation of emerging contaminants

Inspired by the growing development of dual single-atom catalysts (SACs), a bimetallic single-atom alloy (SAA) based macro-assembled graphene aerogel (MAGA) was synthesized in this study. The single-atom NiCo alloy-based graphene aerogel (i.e., NiCo/GO aerogel) with pinning effect was used as a sustainable cathode material in an in-situ H2O2 generation system (i.e., electro-Fenton (EF) process). The atomic structure of NiCo/GO aerogel was identified by the combined microscopic and spectroscopic techniques. The SAA cathode exhibited a remarkable catalytic activity towards the two-electron-dominated oxygen reduction reaction (ORR) with the EF process for wastewater treatment. The energy consumption was calculated to be around 0.660 kW·h/t for treatment of water containing 2 mg L−1 ibuprofen (IBU). Density functional theory (DFT) analysis revealed the specific roles of the dual-functional NiCo SAA in the GO aerogel cathode, i.e., the Co sites more preferentially adsorb O2 molecules for H2O2 generation while the Ni sites function as the active sites for H2O2 dissociation and activation. The research findings shed light on the controlled synthesis of SAAs for advanced catalysis and its potential application in the treatment of emerging organic contaminants for water safety and pollution control.

ANN and DFT investigation of 55-atom icosahedral Ag-Pt nanoalloys: Understanding structure, dynamics, and [formula omitted] activation

An artificial neural network (ANN)–based interatomic potential has been constructed to examine the structural properties of Ag55−nPtn nanoalloys, where n= 0–14. We conducted molecular dynamics simulations for global-optimizations of these nanoalloys using ANN-based interatomic potential. The relative stability of the Ag-Pt nanoalloys has been studied using stability indicators such as cohesive energy, excess energy and interaction energy. Additionally, we analyse the adsorption of O2 and CO molecules on Ag55−nPtn nanoalloys using the first-principles density functional theory based (DFT) method. The presence of Pt doping has been found to increase the adsorption strength of O2 and CO on the Ag55−nPtn nanoalloys compared to the pure Ag55 nanocluster. Our investigation suggests that the presence of Pt atoms in the core of the nanoalloy has a relatively minor effect on the adsorption of O2 and CO in comparison to Pt atoms present on the surface. The adsorption of O2 and CO on Ag41Pt14 nanoalloy, in which one of the Pt atoms is present at the surface of the nanoalloy, shows strongest adsorption among all the compositions of Ag55−nPtn nanoalloys.

Radiative emissions from charge exchange processes in collisions of 0.7–10.0 keV He[formula omitted] with N[formula omitted] and O2 molecules

We present an experimental study of the dissociative excitation in the collision of helium ions with nitrogen and oxygen molecules for collision energy of 0.7–10.0 keV. Absolute emission cross sections are measured and reported for the most pronounced nitrogen and oxygen atomic and ionic lines in vacuum ultraviolet (80–130nm) and visible (380–670nm) spectral regions. Remarkable similarities of the processes realized in He++N2 and He++O2 collision systems are observed. We present polarization measurements for He++N2 collision system.The emission of excited dissociative products was detected using an improved high-resolution optical spectroscopy method. This method incorporates the retarding potential method and a high resolution electrostatic energy analyzer to precisely measure the energy of incident particles and the energy of dispersion. The improvement in the optical sensitivity allows us to measure the cross section on the order of 10−19 cm2 or lower.

Theoretical study of adsorption properties and CO oxidation reaction on surfaces of higher tungsten boride

Most modern catalysts are based on precious metals and rear-earth elements, making some of organic synthesis reactions economically insolvent. Density functional theory calculations are used here to describe several differently oriented surfaces of the higher tungsten boride WB5-x, together with their catalytic activity for the CO oxidation reaction. Based on our findings, WB5-x appears to be an efficient alternative catalyst for CO oxidation. Calculated surface energies allow the use of the Wulff construction to determine the equilibrium shape of WB5-x particles. It is found that the (010) and (101) facets terminated by boron and tungsten, respectively, are the most exposed surfaces for which the adsorption of different gaseous agents (CO, CO2, H2, N2, O2, NO, NO2, H2O, NH3, SO2) is evaluated to reveal promising prospects for applications. CO oxidation on B-rich (010) and W-rich (101) surfaces is further investigated by analyzing the charge redistribution during the adsorption of CO and O2 molecules. It is found that CO oxidation has relatively low energy barriers. The implications of the present results, the effects of WB5-x on CO oxidation and potential application in the automotive, chemical, and mining industries are discussed.

The Effects of Halogen (Cl, Br) Decorating on the Gas Adsorption Behaviors of the Pristine Black Phosphorene: A First-Principles Study

As a novel two-dimensional (2D) material, black phosphorene (BP) finds wide applications in gas adsorption and detection devices due to its distinctive optical, thermoelectric, and surface properties. However, numerous studies have demonstrated that BP exhibits strong selectivity towards gas adsorption and displays significant affinity towards gas molecules containing the element N, thereby greatly impeding its utilization in gas detection. To partially compensate for this deficiency, this study investigates the impact of halogen atom decoration on the adsorption behavior of BP towards CO2, H2O, and O2 molecules. Furthermore, a comparison is made between the variations in gas adsorption energy with and without decorated halogen atoms. The results showed that the adsorbates of CO2, H2O, and O2 molecules and halogen atoms (Cl, Br) adsorbed at the top (T) site of BP was much stronger than those at the bridge (B) and the hollow (H) sites of the P-P bond of BP, owing to their low adsorption energies. After the t position of BP is modified by the halogen (Cl, Br) atom, the optimal adsorption of CO2 changes from −0.85 eV to −1.70 eV (Cl) and −1.64 eV (Br), and the optimal adsorption of H2O changes from −0.72 eV to −1.48 eV (Cl) and −1.23 eV (Br), respectively. The adsorption properties were significantly enhanced. That is to say, the gas adsorption properties of BP have been largely improved by halogen Cl (Br) atoms decorating.

A Study on Dielectric Breakdown Properties of Hot CO2/O2/C5F10O Gas Mixture: Focus on Concentration Rate of O2 Gas

A gaseous mixture of CO2 and C5F10O has been widely investigated as one of the alternative gases for SF6. Due to the better electron attachment ability of oxygen molecule O2, it is generally expected that adding of O2 gas would improve the dielectric strength of arc quenching and insulating gas for electric power equipment. Therefore, in this paper, the dielectric breakdown properties of hot CO2/O2/C5F10O gas mixture were numerically estimated. The calculation results revealed that the critical electric field strength of the CO2/C5F10O gas mixture is disappointingly decreased by the addition of O2 gas, especially in the temperature range of 3000 K to 1000 K. This is brought about by the increase of ionization reaction of CO2 molecules with an increase in the O2 concentration in the arc‐quenching gas of CO2/O2/C5F10O. © 2024 Institute of Electrical Engineers of Japan and Wiley Periodicals LLC.

Toward Monolayered Solar Cells: Luminescence Properties and Light Soaking in TMDs.

The optical and photonic characteristics of monolayer transition metal dichalcogenides (TMDs) play a pivotal role in their functionality as solar cell materials, light-emitting diodes (LEDs), and other electro-optical applications. In this study, we reveal the impact of prolonged illumination on the luminescence properties and Raman spectra of monolayered MoS2 and WS2─a process known as "light soaking". We find a light-induced transition from the physisorption to the chemisorption of ambient O2 and H2O molecules. In parallel, we observe the activation and passivation of defect sites in the samples (depending on their initial defect density), which is attributed to the adsorbed ambient molecules and the resulting light-driven interactions with defect sites. Thus, we can control the active defect density of monolayered TMDs and shed light on the fundamental mechanisms underlying their luminescence properties. Therefore, this work clarifies the source of changes to the luminescence properties of TMDs and opens the path toward their integration into advanced applications that may be affected by light soaking, such as solar cells and energy devices.

Hydroxyl-Bonded Co Single Atom Site on Boroncarbonitride Surface Realizes Nonsacrificial H2O2 Synthesis in the Near-Infrared Region.

Photocatalytic synthesis of hydrogen peroxide (H2O2) from O2 and H2O under near-infrared light is a sustainable renewable energy production strategy, but challenging reaction. The bottleneck of this reaction lies in the regulation of O2 reduction path by photocatalyst. Herein, the center of the one-step two-electron reduction (OSR) pathway of O2 for H2O2 evolution via the formation of the hydroxyl-bonded Co single-atom sites on boroncarbonitride surface (BCN-OH2/Co1) is constructed. The experimental and theoretical prediction results confirm that the hydroxyl group on the surface and the electronic band structure of BCN-OH2/Co1 are the key factor in regulating the O2 reduction pathway. In addition, the hydroxyl-bonded Co single-atom sites can further enrich O2 molecules with more electrons, which can avoid the one-electron reduction of O2 to •O2 -, thus promoting the direct two-electron activation hydrogenation of O2. Consequently, BCN-OH2/Co1 exhibits a high H2O2 evolution apparent quantum efficiency of 0.8% at 850nm, better than most of the previously reported photocatalysts. This study reveals an important reaction pathway for the generation of H2O2, emphasizing that precise control of the active site structure of the photocatalyst is essential for achieving efficient conversion of solar-to-chemical.

Influence of Hf Doping on the Oxygen Behaviors on ZrCo(110) Surface Using First-Principles Calculation

ZrCo alloy is easily poisoned by impurity gases such as O2, CO, and CO2, resulting in a deterioration in hydrogen storage performance. In this study, we conducted a comprehensive investigation into the adsorption and dissociation characteristics of oxygen on the ZrCo(110) surface using first-principles calculations. Previous studies indicated that the anti-disproportionation properties of ZrCo alloy can be significantly improved by Hf substitution, but the effect of Hf doping on the anti-poisoning properties has not been reported. We also examined the effect of Hf doping on the adsorption, dissociation, and diffusion characteristics of oxygen. It is found that on the ZrCo(110) surface, O2 molecules are easily dissociated and then stably adsorbed at the hollow site. Oxygen atoms will fill the surface preferentially and then diffuse inward. The doping of Hf has an insignificant impact on the adsorption or dissociation behavior of oxygen in comparison to the pure ZrCo surface. However, a notable observation is that the doping of Hf resulted in a reduction in the diffusion barrier for oxygen from the surface to the subsurface by 0.61 eV. Consequently, our study suggests that doping Hf is not an advisable strategy for improving the ZrCo(110) surface’s resistance to O2 poisoning because of improved oxygen permeability.

Simulating Vibronic Spectra by Direct Application of Doktorov Formulas on a Superconducting Quantum Simulator.

In this work, a direct quantum implementation of the Doktorov formulas for calculating the vibronic spectrum of molecules under the harmonic approximation is presented. It is applied to the three-atom molecules H2O, SO2, ClO2, HS2, and ZnOH. The method solves the classically hard problem of estimating the Franck-Condon (FC) factors by using the Duschinsky matrices as the only input via the Doktorov quantum circuit. This has the advantage of avoiding basis changes, artificial squeezing parameters, and symmetry dependencies. In other words, it is a general method for three-atom molecules that can easily be generalized to bigger molecules. The results are compared with other quantum algorithms and classical anharmonic algorithms. Furthermore, the circuit requirements are studied in order to estimate its applicability on real superconducting quantum hardware.

Phase segregation and nanoconfined fluid O2 in a lithium-rich oxide cathode

Lithium-rich oxide cathodes lose energy density during cycling due to atomic disordering and nanoscale structural rearrangements, which are both challenging to characterize. Here we resolve the kinetics and thermodynamics of these processes in an exemplar layered Li-rich (Li1.2–xMn0.8O2) cathode using a combined approach of ab initio molecular dynamics and cluster expansion-based Monte Carlo simulations. We identify a kinetically accessible and thermodynamically favourable mechanism to form O2 molecules in the bulk, involving Mn migration and driven by interlayer oxygen dimerization. At the top of charge, the bulk structure locally phase segregates into MnO2-rich regions and Mn-deficient nanovoids, which contain O2 molecules as a nanoconfined fluid. These nanovoids are connected in a percolating network, potentially allowing long-range oxygen transport and linking bulk O2 formation to surface O2 loss. These insights highlight the importance of developing strategies to kinetically stabilize the bulk structure of Li-rich O-redox cathodes to maintain their high energy densities.

Origin of Unprecedented Formation and Reactivity of FeIV═O Species via Oxygen Activation: Role of Noncovalent Interactions and Magnetic Coupling.

Emulating the capabilities of the soluble methane monooxygenase (sMMO) enzymes, which effortlessly activate oxygen at diiron(II) centers to form a reactive diiron(IV) intermediate Q, which then performs the challenging oxidation of methane to methanol, poses a significant challenge. Very recently, one of us reported the mononuclear complex [(cyclam)FeII(CH3CN)2]2+ (1), which performed a rare bimolecular activation of the molecule of O2 to generate two molecules of FeIV═O without the requirement of external proton or electron sources, similar to sMMO. In the present study, we employed the density functional theory (DFT) calculations to investigate this unique mechanism of O2 activation. We show that secondary hydrogen-bonding interactions between ligand N-H groups and O2 play a vital role in reducing the energy barrier associated with the initial O2 binding at 1 and O-O bond cleavage to form the FeIV═O complex. Further, the unique reactivity of FeIV═O species toward simultaneous C-H and O-H bond activation process has been demonstrated. Our study unveils that the nature of the magnetic coupling between the diiron centers is also crucial. Given that the influence of magnetic coupling and noncovalent interactions in catalysis remains largely unexplored, this unexplored realm presents numerous avenues for experimental chemists to develop novel structural and functional analogues of sMMO.

Termolecular Eley–Rideal pathway for catalytic oxidation of nitric oxide on [Pt2]0,± dimers using O2

AbstractA comprehensive density functional theory (DFT) investigation of the catalytic oxidation of NO to NO2 on neutral and charged [Pt2]0,± dimers has been considered employing M06L/def2TZVP level of theory. Single as well as co‐adsorption energies of NO and O2 molecules suggest that the traditional Langmuir Hinshelwood (LH) mechanism and less explored termolecular Eley–Rideal (TER) and termolecular Langmuir Hinshelwood (TLH) mechanisms, are suitable for a full catalytic reaction pathway in which two NO molecules are converted to two NO2 molecules, initiated by an activated O2 molecule. Activation barrier reveals that the TER mechanism is found to be more reliable in converting two NO molecules into two NO2 molecules on [Pt2]¯ dimer. In addition to shedding light on the intrinsic characteristics of Pt2 dimers, the study will serve as a benchmark for investigating the oxidation process of NO to NO2 utilizing models of termolecular chemical processes.

Atomically dispersed magnesium enhancing reactive oxygen species generation over g-C3N4 nanosheets for efficient photocatalytic NO removal

Photoinduced reactive oxygen species (ROSs)-involving nitrogen oxide (NOx) abatement offers a green way to mitigate environmental air pollution. Developing cost-effective photocatalysts remains challenging yet crucial. Herein, an atomically dispersed Mg-modified g-C3N4 nanosheet photocatalyst (xMg-CN) with excellent photoactivity is developed. The 1.0Mg-CN sample delivers a high NO removal rate of 52.3% under visible light irradiation within 30 min, far surpassing the Mg-free analog (CN, 41.2%). Moreover, a suppressed NO2 by-product discharge can be achieved. The introduction of Mg single atoms (SAs) alters the charge density distribution on the triazine ring plane of g-C3N4, inducing the formation of a built-in electric field, which improves the photoexcited charge carrier separation. Additionally, Mg SAs contribute to the adsorption and activation of O2 molecules, resulting in enhanced ROSs production, as evidenced by the experiments and theoretical simulations. The findings shed light on the role of SAs in designing highly efficient g-C3N4-based photocatalysts for air purification.

Understanding of mercury/oxygen reaction mechanism over BiOBr photocatalyst with oxygen vacancy

BiOBr with the advantage of easily generated surface oxygen vacancy, has been considered as a promising photocatalyst for Hg0 oxidation in the flue gas and the active oxygen species is crucial for the oxidation reaction. Nevertheless, the detailed mercury/oxygen reaction mechanism on the BiOBr surface is still unclear and the effect of oxygen vacancy on the reaction process was worth in-depth study. Herein, the oxygen-involved Hg0 oxidation mechanism on the BiOBr surface and the effect of oxygen vacancy were deeply understood by quantum chemistry calculation. The reactivity difference of chemisorbed and lattice oxygen species was revealed. Therein, the chemisorbed oxygen derived from the activation of gaseous O2 molecule showed the higher reactivity than lattice oxygen for Hg0 oxidation reaction. The introduction of oxygen vacancy could promote O2 activation and simultaneously reduce the energy barrier of HgO formation from 1.76 to 1.45 eV. In addition, the energy barrier of oxygen vacancy recovery (0.05 eV) was higher than that of O2 activation (0.02 eV), indicating that the initial oxygen vacancy could be retained in the reaction process. This work deeply revealed the mercury/oxygen reaction mechanism over BiOBr photocatalyst and provided the guidance for the catalyst design in the photocatalytic Hg0 oxidation.