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Two-dimensional transition metal oxides have been widely explored as a catalyst in the high capacity non-aqueous lithium-oxygen batteries due to their excellent electrochemical performance in the o...

Group-III phosphide (MP, M = B, Al, Ga and In) monolayers have promising applications in photocatalysis, nanoelectronics and optoelectronics. Their stabilities in oxygen and water environments are crucial to their practical applications. In order to investigate the stabilities of the MP monolayers, density functional theory calculations combined with ab initio molecular dynamics (AIMD) simulations were performed to illustrate their interactions with oxygen and water molecules. It was found that an oxygen molecule spontaneously dissociates on the AlP, GaP and InP monolayers. In the meantime, the corresponding monolayer structures are severely distorted after annealing. In contrast, BP monolayer is stable in the oxygen environment due to a high dissociative barrier of 0.89 eV. We found that a water molecule dissociates on AlP monolayer with a dissociative energy barrier of 0.42 eV, but it can be stably adsorbed on the BP, GaP and InP monolayers without the breakage of O-H bonds. Nevertheless, with the increase of the number of water molecules, the formed intermolecular H-bonding can promote interactions between water molecules and the monolayers, leading to structural distortion in the GaP and InP monolayers. When putting a water molecule near the oxygen molecule, the oxidation barrier of the BP monolayer is reduced to 0.75 eV, which is still high enough to maintain its stable state. This investigation theoretically provides environmental conditions for the experimental fabrication and practical application of semiconductor monolayers.

Facing the challenge of increasingly severe environmental issues, many researchers are committed to seeking "post lithium-ion batteries" that can replace fossil fuels, one of which is alkali-metal-oxygen batteries. Nevertheless, the main bottleneck restricting the development of these batteries is the need for suitable catalysts to facilitate the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER). In this study, we attempt to modify the catalytic performance of δ-MnO

Alkali metal-oxygen batteries possess a higher specific capacity than alkali-ion batteries and stand out as the most competitive next-generation energy source. The core reaction mechanism of the battery is mainly the formation of alkali metal oxide during the discharge process and the decomposition of these oxides during the charge process. A large number of researchers have devoted themselves to seeking promising catalysts for the reaction. Two-dimensional Nb

Silicene has recently shown high electrochemical performance with discharging product Li2O(s) and high stability, avoiding discharging byproducts for nonaqueous lithium–oxygen batteries. At the fun...

Conversion of dinitrogen (N2) molecules into ammonia through electrochemical methods is a promising alternative to the traditional Haber-Bosch process. However, searching for an eligible electrocatalyst with high stability, low-onset potential, and superior selectivity is still one of the most challenging and attractive topics for the electrochemical N2 reduction reaction (NRR). Here, by means of first-principles calculations and the conductor-like screening model, four comprehensive criteria were proposed to screen out eligible NRR electrocatalysts from 29 atomic transition metals embedded on the defective boron phosphide (BP) monolayer with B-monovacancy (M/BP single-atom catalysts, SAC, M = Sc-Zn, Y-Cd, and Hf-Hg). Consequently, the Nb/BP and W/BP SACs are identified as the promising candidates, on which the N2 molecule can only be activated through the enzymatic pathway with the onset potentials of -0.25 and -0.19 V, and selectivities of 90.5 and 100%, respectively. It is worth noting that the W/BP SAC has the lowest overpotential among the 29 systems investigated. The electronic properties were also calculated in detail to analyze the activity origin. Importantly, the Nb/BP and W/BP SACs possess high thermal stabilities due to that their structures can be retained very well up to 1000 and 700 K, respectively. This work not only provides an efficient and reliable method to screen eligible NRR electrocatalysts but also paves a new way for advancing sustainable ammonia synthesis.

Additional file 1: Table S1. Associations between anaemia and AD biomarkers. Table S2. Associations between the severity of anaemia and AD biomarkers. Table S3. Association of anemia with CSF A��42. Table S4. Association of anemia with CSF A��40. Table S5. Association of anemia with CSF t-tau. Table S6. Association of anemia with CSF p-tau. Table S7. Association of anemia with CSF t-tau/A��42 ratio. Table S8. Association of anemia with CSF p-tau/A��42 ratio. Table S9. Association of anemia with CSF A��42/A��40 ratio. Table S10. Associations between the severity of anaemia and CSF A��42. Table S11. Associations between the severity of anaemia and CSF A��40. Table S12. Associations between the severity of anaemia and CSF t-tau. Table S13. Associations between the severity of anaemia and CSF p-tau. Table S14. Associations between the severity of anaemia and t-tau/A��42 ratio. Table S15. Associations between the severity of anaemia and p-tau/A��42 ratio. Table S16. Associations between the severity of anaemia and A��40/A��42 ratio.

Group-IV phosphide monolayers (MP, M=C, Si, Ge and Sn) provide a versatile platform for photocatalysts, as well as optoelectronic and nanoelectronic devices. Herein, comprehensive first-principles calculations and ab initio molecular dynamics (AIMD) simulations were performed to explore their stabilities in the air. We identified that the MP monolayers have excellent mechanical properties and their carrier mobilities are higher than that of phosphorene. The MP monolayers were predicted to possess superior oxidation resistance than the boron phosphide (BP) monolayer based on the proposed donation-backdonation theory. It was observed that the dissociation and chemisorption of a water molecule on the monolayers are kinetically difficult both in the water and in oxygen-water environments involving energy barriers of 1.28-3.48 eV. We also performed AIMD simulations at 300, 1000, 1200 and 1500 K. It is noteworthy that only the carbon phosphide (CP) monolayer can retain an intact structure at 1500 K, while the other three monolayers can just sustain to 1200 K. These results provide a guidance for their practical application and experimental fabrication.

Direct methanol fuel cell (DMFC) running on hydrogen is an attractive alternative power source for a wide range of applications. Importantly, the required hydrogen can be in situ released from the stable liquid, which ensures its safe transformation and storage. However, the catalyst in DMFC is usually poisoned by the generated CO species, thus it is challenging to find an efficient and durable catalyst for practical applications. Here, the mechanism of methanol oxidation reaction (MOR) on the Mo2P monolayer is first studied using density functional theory. Compared with the initial C–H and C–O bond scissions, the initial O–H bond scission is found to be the most favorable. The reason is systematically analyzed based on steric effect, activation Gibbs free energy (Gact) decomposition and the Bronsted − Evans − Polanyi (BEP) relationships. The further dehydrogenation of CH2OH via the O–H bond scission has a significantly lower Gact than that of CH3O, thus the methanol decomposition on the Mo2P monolayer may proceed via two competitive pathways, i.e., CH 3 OH → CH 3 O → CH 2 O → CHO → CO and CH 3 OH → CH 2 OH → CH 2 O → CHO → CO . Then, through overcoming a relatively low barrier, the generated CO species can be combined with hydroxyl group from water dissociation on the Mo2P monolayer to produce formic acid, which can be easily desorbed from the catalyst surface to avoid the block of active sites. This study provides a better understanding of the MOR mechanism and paves the way for further advancing the catalyst in DMFCs.

The data reported in this article are structural and physicochemical properties for bare and F, O, OH and CH3O-functionalized Nb n+1C n (n = 1, 2, 3 and 4) MXenes. The structural properties are presented as top views and side views from the X direction of the optimal structures of studied MXenes. The physicochemical properties include quantum capacitances, electrostatic potentials and electronic properties such as the projected density of states (PDOS) and band structures. Further interpretation and discussion of these data can be obtained from the article entitled "Possibility of bare and functionalized niobium carbide MXenes for electrode materials of supercapacitors and field emitters" (Xin and Yu, 2017) [1].

The main objective of this study is density functional theory investigations on adsorption and decomposition of N 2 O on ZnO(0001)-G nanocomposite. The adsorption and decomposition of small molecules on the magnetic oxides containing transition metals are relatively rare due to the modeling difficulties using current density functional approximations. A molecular modeling of the reaction mechanism was studied in this work through ab initio modeling of the catalytic adsorption and decomposition of N 2 O on ZnO(0001)-G. DFT was used to study the molecular mechanism of conceivable elementary steps of the decomposition of N 2 O over the most stable (0001) surface. Three reactions including the N 2 O bond cleavage, the oxygen atom transfer, forming a surface peroxy group O 2 2− were studied. The horse-like (N N O), parallel (N N O) and lying-atop-011 (O N N) with all three atoms of the N 2 O molecule interacting with the surface have been found as more stable adsorption forms, which have adsorption energies of −0.27, −0.23 and −0.23 eV, respectively. The activation energies of the N 2 O decomposition through mentioned reactions were found to be 2.73, 0.48 and 0.63 eV, respectively. The obtained results reveal that ZnO(0001)-G is not only an efficient but also a green catalyst in comparison with others such as Mn-G.

The boundary between quantum capacitance and pseudocapacitance is blurred due to their similarity in electronic populations. Here we propose the rules to classify the contributions of quantum capacitance and pseudocapacitance and their effects on the intrinsic ion transport kinetics based on the applied voltages and electronic structures. Systems including graphite, LiFePO4, LiTiS2, LiCoO2, and Ti3C2Tx MXene are employed to illustrate their different intrinsic kinetics according to the classifications based on the density functional theory calculations and the reported experimental measurements. These results can facilitate the step to screen the electrode materials with different kinetics through calculations.