SwePub - sökning: WFRF:(Yang Xiaoyong)

Numrering	Referens	Omslagsbild	Hitta
1.	2019 Tidskriftsartikel (refereegranskat)
2.	Yang, Xiaoyong, et al. (författare) Investigating the solution and diffusion properties of hydrogen in alpha-Uranium by first-principles calculations 2020 Ingår i: Progress in nuclear energy (New series). - : PERGAMON-ELSEVIER SCIENCE LTD. - 0149-1970 .- 1878-4224. ; 122 Tidskriftsartikel (refereegranskat)abstract The stability, solution and diffusion properties of an interstitial hydrogen atom in uranium metal have been firstly investigated by first-principles calculations. In energy, the octahedral site is more favorable for hydrogen to occupy than tetrahedra site with neglectable anisotropic perturbation. Besides, the effects of temperature on solution energy are quantified, which demonstrate the solution energy decreases fast with temperature. The calculated density of states and electronic charge re-distribution are analyzed. It is found the conductivity of metal uranium remains well after hydrogen occupied the interstitial position with lower concentration. The minimum migration pathways of interstitial hydrogen in uranium lattice are characterized by the climbing image nudged elastic band (CINEB) method. The obtained energy barriers are 0.239 eV, 0.298 eV and 0.313 eV with respect to O <-> T, O <-> O and T <-> T pathways with feeble structural deterioration. We believe our results for hydrogen diffusion in such a complex f -electron system not only provide en evidence for uranium corrosion but also supports the future experiments on measuring the hydriding rate and their interpretations.
3.	Yang, Xiaoyong, et al. (författare) Structural, electronic, mechanical and thermodynamic properties of U-Si intermetallic compounds : A comprehensive first principles calculations 2022 Ingår i: Progress in nuclear energy (New series). - : Elsevier BV. - 0149-1970 .- 1878-4224. ; 148, s. 104229- Tidskriftsartikel (refereegranskat)abstract Uranium silicides are proposed as the prominent accident tolerant fuels for the light water reactors (LWR) due to their high metal density and high thermal conductivity. Among the U-Si alloys, the alloy with high U:Si ratio is more favorable for nuclear fuel application due to the higher uranium density. Thus, the crystal structure, mechanical property, electronic structure, phonon band structure and thermodynamic property of U3Si, U3Si2 and USi compounds, along with the thermodynamic reaction between U-Si intermetallic compounds are systematically studied in our work. The optimized structural parameters of these U-Si alloys are comparable with previous results. Besides, all of them are metallic in nature. Since the calculated elastic constants satisfy the Born stability criteria, one can know U-Si alloys are mechanically stable. The phonon dispersion curves are obtained based on the density functional perturbation theory (DFPT). Accordingly, various thermophysical properties, such as Helmholtz free energy, heat capacity, internal energy and entropy are calculated. Furthermore, the reaction energies related to the formation of U3Si, U3Si2 and USi as well as transformation between them are calculated. It is revealed at the same chemical environment the reaction to form USi occurs more easily, whereas the high temperature and sufficient uranium environment are more in favor for fully silicification of uranium metal into U3Si. Theoretical investigation of this work is expected to provide some new insights for the application of uranium silicides as nuclear fuels and future exploration on the design and synthesis of new-type uranium silicides.
4.	Fang, Xing, et al. (författare) Microstructure and mechanical properties of the laser welded air-hardening steel joint 2024 Ingår i: Materials Characterization. - : Elsevier BV. - 1044-5803 .- 1873-4189. ; 213 Tidskriftsartikel (refereegranskat)abstract The decrease in mechanical properties of high-strength steel after welding is an important issue affecting the wide application of high-strength steel. Air-hardening steel is a high-strength steel suitable for lower body structural parts such as subframes. Its application process involves welding, hot forming and other processes. The present work investigates the microstructure and mechanical properties of the air-hardening steel laser welded joint that is air-cooled after hot forming in the two-phase zone (800 °C). The microstructure was characterized by electron backscattered diffraction (EBSD), scanning electron microscope (SEM) and transmission electron microscope (TEM). The results show that during hot forming, the welded joint transforms from martensite to ferrite and acicular martensite, and the base metal transforms from ferrite to polygonal martensite and ferrite. The difference in martensite morphology between the welded joint and the base metal is attributed to the nucleation positions of austenite. The structural evolution of the welded joint and the base metal is accompanied with the annihilation and reproduction of dislocations, which results in significant changes in hardness. The hardness value dropped from the highest 430 HV to 271 HV in the welded joint, while increased from the lowest 184 HV to 203 HV in the base metal. After hot forming, the tensile strength of the welded sample is reduced by only 36 MPa, and the total elongation is slightly decreased by about 1.5% compared with the unwelded sample. The welded joint and the base metal have similar plastic deformation capabilities, since the acicular martensite in the welded joint displays good plastic deformation ability, and the dislocation density of the welded joint and the base metal is similar. Overall, the microstructure and dislocation density of the air-hardening steel welded joint after hot forming are similar to those of the base metal, which is responsible for the good mechanical properties of air-hardening steel welded joint.
5.	Fang, Zhiwei, et al. (författare) Structural stability and aqueous durability of Cs incorporation into BaAl2Ti6O16 hollandite 2022 Ingår i: Journal of Nuclear Materials. - : Elsevier BV. - 0022-3115 .- 1873-4820. ; 565, s. 153716- Tidskriftsartikel (refereegranskat)abstract Hollandite ceramics are well-recognized as a promising host for immobilizing radioactive cesium. In the present paper, the [BaxCsy][(Al3+,Ti3+)(2x +y)Ti-8-2x-y(4+)]O-16 (0.4 <= x, y <= 0.8) ceramics were fabricated to in-vestigate the effect of incorporated Cs on structural stability and durability of (Ba,Cs)(Al,Ti)(8)O-16 ceramics with Cs-incorporated. It was found that the sintered samples at 1250 degrees C show a pure hollandite phase with tetragonal structure (I4/m) and high Cs retention. Moreover, the synthesized (Ba,Cs)(Al,Ti)(8)O-16 ceramics exhibit an excellent aqueous stability and the normalized Cs release rate is 2.82 (+/- 0.27) x10(-3) g m(-2) d(-1) after 28 days. All these results reveal that (Ba,Cs)(Al,Ti)(8)O-16 is a promising candidate as a Cs-waste form.
6.	Li, Shuyang, et al. (författare) Efficient photoreduction strategy for uranium immobilization based on graphite carbon nitride/perovskite oxide heterojunction nanocomposites 2021 Ingår i: Applied Catalysis B. - : Elsevier BV. - 0926-3373 .- 1873-3883. ; 298 Tidskriftsartikel (refereegranskat)abstract The photoreduction conversion of soluble U(VI) to insoluble U(IV) is an economical strategy for the efficient removal of uranium from radioactive wastewater. A graphite carbon nitride and pemvskite oxide heterojunction composite (g-C3N4/LaFeO3) is designed for the photocatalytic reduction of U(VI) under simulated sunlight conditions from aqueous solution, the reduction-immobilization mechanism is interpreted with the aid of spectroscopic evidence. The proposed heterojunction structure exhibits efficient removal ability (460 mg/g) over a wide range of U(VI) concentrations due to the suppressed recombination of photogenerated electron-hole pairs and the prolonged lifetimes of the photogenerated carriers. The catalytic efficiency is maintained at a high level after five cycles of reuse. The electrons on LaFeO3 transferred to valence band of g-C3N4, U(VI) is reduced by the electrons and center dot O-2(-) on the surface of g-C3N4. The g-C3N4/LaFeO3 heterojunction provides a promising strategy for the feasible recovery of U(VI) resources with inexhaustible solar energy.
7.	Ma, Jiang, et al. (författare) Investigating hollandite-perovskite composite ceramics as a potential waste form for immobilization of radioactive cesium and strontium 2021 Ingår i: Journal of Materials Science. - : Springer Nature. - 0022-2461 .- 1573-4803. ; 56:16, s. 9644-9654 Tidskriftsartikel (refereegranskat)abstract Ceramic matrix containing zirconolite, hollandite, and perovskite phases is proposed as a potential host for HLW immobilization. Hollandite phase principally immobilizes Cs, while perovskite phase mainly immobilizes Sr. In this study, hollandite–perovskite composite ceramics are considered as a specialized waste form for immobilizing the separated Cs and Sr from HLW streams and synthesized by a solid-state reaction method at 1300 °C for 5 h. The phase compositions of the synthesized composites were characterized by XRD and BSE. The XRD results indicated that the as-prepared ceramics are composed of tetragonal hollandite Ba0.8Cs0.4Al2Ti6O16, cubic perovskite SrTiO3, alongside a lesser amount of TiO2. The BSE—EDX results confirm that Cs partitions into the hollandite matrix, while Sr incorporates into perovskite host with homogenous distribution. In addition, aqueous durability testing was carried out using the MCC-1 static leach test method. The normalized release rates of Cs and Sr in HP-3 sample (i.e., 75 wt% Ba0.8Cs0.4Al2Ti6O16 + 25 wt% SrTiO3) were < 10−2 g·m−2·d−1 after 42 days, exhibiting excellent chemical durability. These results indicate that the hollandite–perovskite ceramic matrix could be considered as a customized host matrix for immobilization of the separated Cs and Sr from HLW streams.
8.	Wang, Xin-Xin, et al. (författare) What is the Role of Nb on Preferential Hydriding of Double-Phased Uranium, Stabilizing gamma-U, or Avoiding Hydrogen Aggregation? 2021 Ingår i: The Journal of Physical Chemistry C. - : American Chemical Society (ACS). - 1932-7447 .- 1932-7455. ; 125:17, s. 9364-9370 Tidskriftsartikel (refereegranskat)abstract Uranium as the heaviest naturally occurring element plays important roles in nuclear industries. Hydrogen-caused corrosions and irradiation-caused structural damages are two critical degradations that threaten the safe storage and practical applications of uranium. Through alloying with transition metals like Nb, the gamma-phase of U can be stabilized at room temperature, which shows better performance against hydrogen-caused corrosions than the ground-state alpha-U. The underlying mechanisms have not been fully understood yet. To explain the preferential hydriding phenomenon observed on a specially fabricated double-phase U-2.5 wt % Nb alloy, we perform multiscale ab initio calculations and kinetic Monte Carlo (KMC) simulations. We find that because of different diffusion mechanisms, intrinsic alpha-U and gamma-U already show different hydrogen accumulation behaviors. The existence of random Nb atoms further inhibits hydrogen accumulation in gamma-U. Our work declares its contribution by pointing out the important role of crystal lattice architectures on hydrogen accumulations in metals.
9.	Ba, Kun, et al. (författare) Billiard Catalysis at Ti3C2 MXene/MAX Heterostructure for Efficient Nitrogen Fixation 2022 Ingår i: Applied Catalysis B. - : Elsevier BV. - 0926-3373 .- 1873-3883. ; 317, s. 121755- Tidskriftsartikel (refereegranskat)abstract Electrocatalytic ammonia (NH3) conversion under ambient atmosphere is crucial to mimic the nature's nitrogen cycle. But currently it is always interrupted by the HER process which is more competitive. Herein, we tactically cultivate a series of incompletely etched Ti3AlC2 MAX / Ti3C2 MXene based heterostructure catalysts whose composition can be finely tuned through regulation of the LiF percentage in mixed chemical etching agent. Notably, the surface potential difference between MAX and MXene is ~40 mV, indicating that the electron can be readily transferred from MAX to MXene across the interfaces, which is favorable for N2 fixation, yielding an outstanding Faradic efficiency of 36.9%. Furthermore, density functional theory calculations reveal the billiard-like catalysis mechanism, where the intermediates are alternatively adsorbed on MAX or MXene surfaces. Meanwhile, the rate-determining step of NH → NH2 possesses an energy barrier of 0.96 eV on the hetero-interface which follows associative distal mechanism. This work opens a new frontier of heterostructured catalyst for balancing electrical conductivity and catalytic activity in electrocatalysis.
10.	Chen, Xue, et al. (författare) Co-Doped Fe3S4Nanoflowers for Boosting Electrocatalytic Nitrogen Fixation to Ammonia under Mild Conditions 2022 Ingår i: Inorganic Chemistry. - : American Chemical Society. - 0020-1669 .- 1520-510X. ; 61:49, s. 20123-20132 Tidskriftsartikel (refereegranskat)abstract Compared with the Haber Bosch process, the electrochemical nitrogen reduction reaction (NRR) under mild conditions provides an alternative and promising route for ammonia synthesis due to its green and sustainable features. However, the great energy barrier to break the stable NN bond hinders the practical application of NRR. Though Fe is the only common metal element in all biological nitrogenases in nature, there is still a lack of study on developing highly efficient and low-cost Fe-based catalysts for N2fixation. Herein, Co-doped Fe3S4nanoflowers were fabricated as the intended catalyst for NRR. The results indicate that 4% Co-doped Fe3S4nanoflowers achieve a high Faradaic efficiency of 17% and a NH3yield rate of 37.5 μg·h-1·mg-1cat.at-0.55 V versus RHE potential in 0.1 M HCl, which is superior to most Fe-based catalysts. The introduction of Co atoms can not only shift the partial density states of Fe3S4toward the Fermi level but also serve as new active centers to promote N2absorption, lowering the energy barrier of the potential determination step to accelerate the catalytic process. This work paves a pathway of the morphology and doping engineering for Fe-based electrocatalysts to enhance ammonia synthesis.
11.	Gao, Chan, et al. (författare) Defect evolution behaviors from single sulfur point vacancies to line vacancies in monolayer molybdenum disulfide 2021 Ingår i: Physical Chemistry, Chemical Physics - PCCP. - : Royal Society of Chemistry. - 1463-9076 .- 1463-9084. ; 23:35, s. 19525-19536 Tidskriftsartikel (refereegranskat)abstract Two-dimensional monolayer transition metal dichalcogenides (TMDs) are promising candidates for many novel nanoelectronic and optoelectronic applications due to their exceptional electronic, optical, chemical and mechanical properties. Experimentally, single chalcogen point vacancies caused by electron beam irradiation are found to agglomerate into line vacancy defects in monolayer TMDs. Herein, the corresponding defect evolution behaviors from single sulfur point vacancies to line vacancies in the monolayer molybdenum disulfide (MoS2) have been systematically studied using molecular dynamics and first principles calculations. The experimental observations of the defect evolution from single sulfur point vacancies to line vacancies are reproduced at the atomic level. The results indicate that the di-vacancy line defect and a point vacancy separated by a sulfur atom in a line evolve into tri-vacancy line defects, and the di-vacancy line defects can rotate 60 degrees clockwise or counterclockwise. Moreover, two adjacent di-vacancy line defects with an angle of 120 degrees can evolve into tri-vacancy line defects. High temperature and large vacancy concentrations promote the defect evolution from point vacancies to line vacancies. Intriguingly, compared with the randomly distributed point vacancy defects, the line vacancy defects formed after the defect evolution significantly decrease the mechanical properties, such as the ultimate strength, ultimate strain and Young's modulus of monolayer MoS2. In addition, the mechanical properties decrease with increasing vacancy concentration and temperature for the final configurations after defect evolution in monolayer MoS2 with different vacancy concentrations at different temperatures. The band gaps of monolayer MoS2 with line vacancy defects are smaller than those with randomly distributed point vacancy defects. Therefore, our study clarifies the defect evolution behaviors from single sulfur point vacancies to line vacancies in monolayer MoS2 and opens an opportunity for the novel nanoelectronic and optoelectronic applications of monolayer TMDs.
12.	Gao, C., et al. (författare) Machine learning-enabled band gap prediction of monolayer transition metal chalcogenide alloys 2022 Ingår i: Physical Chemistry, Chemical Physics - PCCP. - : Royal Society of Chemistry (RSC). - 1463-9076 .- 1463-9084. ; 24:7, s. 4653-4665 Tidskriftsartikel (refereegranskat)abstract Monolayer transition metal dichalcogenide (TMD) alloys with tunable direct band gaps have promising applications in nanoelectronics and optoelectronics. The composition-dependent band gaps of ternary, quaternary and quinary monolayer TMD alloys have been systematically studied combining density functional theory and machine learning models in the present study. The excellent agreement between the DFT-calculated band gaps and the ML-predicted values for the training, validation and test datasets demonstrates the accuracy of our machine learning based on a neural network model. It is found that the band gap bowing parameter is closely related to the difference between the band gaps of the endpoint material compositions of the monolayer TMD alloy and increases with increasing band gap difference. The band gap bowing effects of monolayer TMD alloys obtained by mixing different transition metals are attributed to the conduction band minimum positions, while those of monolayer TMD alloys obtained by mixing different chalcogen atoms are dominated by the valence band maximum positions. This study shows that monolayer TMD alloys with tunable direct band gaps can provide new opportunities for band gap engineering, as well as electronic and optoelectronic applications.
13.	Gao, Chan, et al. (författare) Synergistic vacancy defects and mechanical strain for the modulation of the mechanical, electronic and optical properties of monolayer tungsten disulfide 2021 Ingår i: Physical Chemistry, Chemical Physics - PCCP. - : Royal Society of Chemistry. - 1463-9076 .- 1463-9084. ; 23:10, s. 6298-6308 Tidskriftsartikel (refereegranskat)abstract Monolayer transition metal dichalcogenides (TMDs) are the potential candidate materials in nanoelectronic and optoelectronic applications due to their unique physical and chemical properties. Although both defect and strain greatly alter the structural, physical and chemical properties of monolayer TMDs, the defective monolayer TMDs under applied strain have not been adequately studied. In this paper, the synergistic effects of sulfur vacancy defects and mechanical strain on the mechanical, electronic and optical properties of monolayer tungsten disulfide (WS2) have been systematically studied using first principles density functional theory. The results indicate that the sulfur vacancy formation energy increases linearly with increasing sulfur vacancy concentration under different strains. The strain energy and stress of monolayer WS2 with different sulfur vacancy concentrations increase with increasing applied strain in the strain range of -10% to 10%. The band gap of monolayer WS2 decreases with increasing sulfur vacancy concentration under different strains. Moreover, compared with unstrained conditions, 5% compressive strain increases the band gap at a larger vacancy concentration and the case is just opposite at a smaller vacancy concentration, while 5% tensile strain decreases the band gap. The band gap of monolayer WS2 with different sulfur vacancy concentrations firstly increases and then shrinks with increasing applied strain under compressive strain, whereas it decreases monotonically under tensile strain in the strain range of -10% to 10%. In the visible-light wavelength region, the out-of-plane absorption coefficient under different strains increases with increasing sulfur vacancy concentration. Furthermore, 5% compressive strain enhances the absorption coefficient and 5% tensile strain decreases the absorption coefficient. Hence, the synergistic effects of sulfur vacancy defects and mechanical strain in monolayer TMDs can open new avenues for their applications in nanoelectronic and optoelectronic devices.
14.	Luo, Zhihui, et al. (författare) Revealing the Charge Storage Mechanism of Nickel Oxide Electrochromic Supercapacitors 2020 Ingår i: ACS Applied Materials and Interfaces. - : AMER CHEMICAL SOC. - 1944-8244 .- 1944-8252. ; 12:35, s. 39098-39107 Tidskriftsartikel (refereegranskat)abstract Nickel oxide (NiO) is considered one of the most promising positive anode materials for electrochromic supercapacitors. Nevertheless, a detailed mechanism of the electrochromic and energy storage process has yet to be unraveled. In this research, the charge storage mechanism of a NiO electrochromic electrode was investigated by combining the in-depth experimental and theoretical analyses. Experimentally, a kinetic analysis of the Li-ion behavior based on the cyclic voltammetry curves reveals the major contribution of surface capacitance versus total capacity, providing fast reaction kinetics and a highly reversible electrochromic performance. Theoretically, our model uncovers that Li ions prefer to adsorb at fcc sites on the NiO(1 1 1) surface, then diffuse horizontally over the plane, and finally migrate in the bulk. More significantly, the calculated theoretical surface capacity (106 mA h g(-1)) accounts for about 77.4% of the total experimental capacity (137 mA h g(-1)), indicating that the surface storage process dominates the whole charge storage, which is in accordance with the experimental results. This work provides a fundamental understanding of transition-metal oxides for application in electrochromic supercapacitors and can also promote the exploration of novel electrode materials for high-performance electrochromic supercapacitors.
15.	Majumdar, Arnab, et al. (författare) High exothermic dissociation in van der Waals like hexagonal two dimensional nitrogene from first-principles molecular dynamics 2020 Ingår i: Applied Surface Science. - : Elsevier. - 0169-4332 .- 1873-5584. ; 529 Tidskriftsartikel (refereegranskat)abstract Mono and multilayered two dimensional (2D) nitrogene in which nitrogen atoms are single bonded are studied for energy applications. The structures are observed to be dynamically and thermally stable at room temperature but dissociate into triple bonded N-2 molecules at higher temperatures. From ab initio molecular dynamics simulations, the dissociation temperature is found to be decreasing with increasing number of layers (1500 K for single layer and 500 K for six layers). The energy released for the different layered cases is large due to the energy difference between single and triple-bonded nitrogen (similar to 0.88 - 1.8 eV/atom). Significantly high energy densities calculated for the multilayered structures (similar to 6 - 12.3 kJ/gm) can secure these materials an important position amongst non-nuclear and inorganic high energy density materials known today. We believe that this work will shed light on synthesizing next generation non-nuclear environmentally clean high energy density materials using multi-layer nitrogene that detonate at not very high temperatures.
16.	Meng, Qi, et al. (författare) Photo-enhanced uranium recovery from spent fuel reprocessing wastewater via S-scheme 2D/0D C3N5/Fe2O3 heterojunctions 2024 Ingår i: SusMat. - : Wiley. - 2766-8479. ; 4:2 Tidskriftsartikel (refereegranskat)abstract Re-extracting environmentally transportable hexavalent uranium from wastewater produced by spent fuel reprocessing using the photocatalytic technology is a crucial strategy to avoid uranium pollution and recover nuclear fuel strategic resources. Here, we have designed S-scheme 2D/0D C3N5/Fe2O3 heterojunction photocatalysts based on the built-in electric field and the energy band bending theory, and have further revealed the immobilization process of hexavalent uranium conversion into relatively insoluble tetravalent uranium in terms of thermodynamics and kinetics. According to the results, the hexavalent uranium removal and recovery ratios in wastewater are as high as 93.38% and 83.58%, respectively. Besides, C3N5/Fe2O3 heterojunctions also exhibit satisfactory catalytic activity and selectivity even in the presence of excessive impurity cations (including Na+, K+, Ca2+, Mg2+, Sr2+, and Eu3+) or various organics (such as xylene, tributylphosphate, pyridine, tannic acid, citric acid, and oxalic acid). It is believed that this work can provide a potential opportunity for S-scheme heterojunction photocatalysts to re-enrich uranium from spent fuel wastewater.
17.	Tsuppayakorn-aek, Prutthipong, et al. (författare) Route to high-T-c superconductivity of BC7 via strong bonding of boron-carbon compound at high pressure 2020 Ingår i: Scientific Reports. - : Springer Nature. - 2045-2322. ; 10:1 Tidskriftsartikel (refereegranskat)abstract We have analyzed the compositions of boron-carbon system, in which the BC7 compound is identified as structural stability at high pressure. The first-principles calculation is used to identify the phase diagram, electronic structure, and superconductivity of BC7. Our results have demonstrated that the BC7 is thermodynamically stable in the diamond-like P4m2 structure at a pressure above 244 GPa, and under temperature also. Feature of chemical bonds between B and C atoms is presented using the electron localization function. The strong chemical bonds in diamond-like P4m2 structure are covalent bonds, and it exhibits the s-p hybridization under the pressure compression. The Fermi surface shape displays the large sheet, indicating that the diamond-like P4m2 phase can achieve a high superconducting transition temperature (T-c). The outstanding property of BC7 at 250 GPa has manifested very hig h-T-c of superconductivity as 164 K, indicating that the carbon-rich system can induce the high-T-c value as well.
18.	Yan, Xiaoyong, et al. (författare) Benford's Law and the First Letter of Words 2018 Ingår i: Physica A. - : Elsevier. - 0378-4371 .- 1873-2119. ; 512, s. 305-315 Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract A universal First-Letter Law (FLL) is derived and described. It predicts the percentages of first letters for words in novels. The FLL is akin to Benford’s law (BL) of first digits, which predicts the percentages of first digits in a data collection of numbers. Both are universal in the sense that FLL only depends on the numbers of letters in the alphabet, whereas BL only depends on the number of digits in the base of the number system. The existence of these types of universal laws appears counter-intuitive. Nonetheless both describe data very well. Relations to some earlier works are given. FLL predicts that an English author on the average starts about 16 out of 100 words with the English letter ‘t’. This is corroborated by data, yet an author can freely write anything. Fuller implications and the applicability of FLL remain for the future.
19.	Yang, Xiaoyong, et al. (författare) An emerging Janus MoSeTe material for potential applications in optoelectronic devices 2019 Ingår i: Journal of Materials Chemistry C. - : ROYAL SOC CHEMISTRY. - 2050-7526 .- 2050-7534. ; 7:39, s. 12312-12320 Tidskriftsartikel (refereegranskat)abstract Motivated by the extraordinary physical and chemical properties of Janus transition-metal dichalcogenides (TMDs) due to the change of the crystal field originating from their asymmetry structures, the electronic and optical properties of the MoSeTe monolayer in 2H and 1T phases are systematically studied by first-principles calculations, and a detailed comparison with the parental MoSe2 and MoTe2 monolayer is made. It is found that 2H-MoSeTe exhibits a direct bandgap of 1.859 eV and an indirect band gap of 0.391 eV in the 1T phase, resulting in a different way to interact with sunlight. Besides, the obtained results show that the SOC has little effects on the band gaps. The calculated optical properties show a significant red shift from the MoSe2 to MoSeTe to MoTe2 monolayer. However, a blue shift is observed from the in-plane to out-of-plane direction. Moreover, both electron-electron and electron-hole correlation effects are considered for obtaining the optical spectra of systems by G(0)W(0) and G(0)W(0) + BSE approaches. Besides, the absorption coefficient value reaches up to 1 x 10(6) cm(-1) in both phases, implying the high efficiency in the utilization of solar energy for the MoSeTe monolayer. Additionally, the 1T-MoSeTe monolayer is a good hot mirror material in that its maximum reflectivity could reach up to 51% in the infrared region. Additionally, the average optical absorbance of the Janus MoSeTe monolayer in the visible light region is calculated to be about 2% and the corresponding average transmittance is around 80%. More importantly, the difference in the optical response for the two side surfaces is considered in our work due to the intrinsic asymmetric structure of Janus MoSeTe. These results not only predict the great potential application of Janus MoSeTe in optoelectronics-electronic devices, but may enable the discovery of new optical science and the realization of various light emissions, detection, modulation and manipulation functions of specific frequencies.
20.	Yang, Xiaoyong, et al. (författare) Enhanced overall water splitting under visible light of MoSSe vertical bar WSSe heterojunction by lateral interfacial engineering 2021 Ingår i: Journal of Catalysis. - : Elsevier. - 0021-9517 .- 1090-2694. ; 404, s. 18-31 Tidskriftsartikel (refereegranskat)abstract Photocatalytic splitting water is a promising method to obtain hydrogen energy. While design and synthesis of efficient and economical photocatalysts is one of the important contents. Janus MoSSe and WSSe monolayers are efficient and wide sunlight harvesting photocatalysts due to their intrinsic vertical electric fields. So how is the photocatalytic performance of lateral MoSSe vertical bar WSSe heterojunctions, which possesses an intra-plane interface and intrinsic vertical electric field? In the present work, the structural property, electronic characteristic, optical property, and photocatalytic application of MoSSe vertical bar WSSe lateral heterojunctions are systematically investigated. It is found that both zigzag and armchair configurations are semiconductors with suitable bandgaps of similar to 1.60 eV. Besides, they possess a type-II band alignment where electrons tend to accumulate at the coupling interface of MoSSe side and holes at WSSe side, giving rise to a paralleled electric field in heterojunctions, which can largely promote the separation of photo-generated carriers. More remarkably, these heterojunctions exhibit pronounced solar-spectrum absorption efficiency, proper valence, and conduction band positions by initializing the redox reactions of H2O and high carrier mobility. Intriguingly, the zigzag MoSSe vertical bar WSSe heterojunction has a better photocatalytic performance in an acidic environment, and the armchair MoSSe vertical bar WSSe prefers to produce H-2 and O-2 in a neutral environment. These fascinating properties render the intra-plane MoSSe vertical bar WSSe heterojunctions as the wide solar harvesting photocatalysts in further overall water splitting.
21.	Yang, Xiaoyong, et al. (författare) Fluoride ion batteries : Designing flexible M2CH2 (M=Ti or V) MXenes as high-capacity cathode materials 2020 Ingår i: Nano Energy. - : Elsevier. - 2211-2855 .- 2211-3282. ; 74 Tidskriftsartikel (refereegranskat)abstract The new concept of rechargeable fluoride ion batteries (FIBs) could potentially be safer, cheaper and higher energy density than those of traditional batteries. However, due to the higher working temperature (~340 K) and the choice of electrolytes and electrodes with excellent electrochemical performance, FIBs are not utilized in daily life yet. In our work, we have systematically investigated several critical parameters of M2CH2 (M = Ti or V) MXenes to assess their performances as cathode materials for rechargeable FIBs, including energetic stability and thermal dynamic stability, electronic property, strain-driven ionic mobility, average open circuit voltage and theoretical specific capacity. Specifically, the ground state structures of M2CH2 are firstly confirmed and then F ion adsorption behavior on the substrate is investigated. Sequentially, F− microscopic diffusion path and migration barrier are identified with and without driven by strain. It reveals that Ti2CH2 displays a lower F− diffusion energy barrier than that of V2CH2 monolayer in a large strain span. Besides, an appropriate control of compression strain could effectively increase the F− mobility due to the change of surface state on Ti2CH2. Importantly, the obtained results show that the F− intercalation into Ti2CH2 exhibits a larger storage capacity (488 mA h g−1) and higher open circuit voltage (4.62 V) than these into V2CH2 monolayer. Moreover, ab initio molecular dynamics (AIMD) calculations prove F2Ti2CH2 is thermo-dynamically stable at 500 K, while, HF compound emerges on F2V2CH2 monolayer at 300 K, implying that Ti2CH2 cathode is possible to work at harshest environment. A combination of these key parameters, we demonstrate that Ti2CH2 monolayer has potential to be a flexible and strain-controllable cathode material for rechargeable FIBs. We hope our detailed investigations could serve as a motivation and provide valuable insights for future experiments to design flexible and dynamically stable cathode materials of high-performance FIBs.
22.	Yang, Xiaoyong, et al. (författare) Hybrid-Density Functional Calculations of Structural, Electronic, Magnetic, and Thermodynamic Properties of alpha-Cu2P2O7 2023 Ingår i: Applied Sciences. - : MDPI AG. - 2076-3417. ; 13:1 Tidskriftsartikel (refereegranskat)abstract We present a comparative study (using PBE, PBE0, and HSE functionals) of electronic and atomic structure, magnetism, and phonon dispersion relations of a-Cu2P2O7. Four possible magnetic configurations are considered, FM, AFM-1, AFM-2, and AFM-3. The calculations reveal that a-Cu(2)P2O(7) is mechanically and thermodynamically stable. The elastic moduli indicate a weak resistance of the compound to volume and shear deformations. The electronic structure at the valence band maximum is dominated by O, with a small admixture of Cu-d(x2-y2) states. The conduction band results from the hybridization between Cu and O states which, in the case of AFM-2, produces the largest band gap of 3.966 eV and the smallest magnetic moment of +/- 0.785 m B on Cu. AFM-2 is found to be the lowest-energy structure that may be viewed as consisting of quasi-one-dimensional Cu1 Cu-2 Cu-3 Cu-4 chains along the b axis; the antiferromagnetism is due to two identical Cu O Cu paths with a bond angle of 100.301 ffi. The phonon spectra exhibit four distinct frequency ranges corresponding to different vibrational modes of ions and ionic groups. Thus, a quantitative description of the structural, electronic, and magnetic properties of alpha-Cu(2)P2O(7) is possible using the HSE hybrid functional, which enables computational studies of transition metal pyro compounds.
23.	Yang, Xiaoyong, et al. (författare) Interfacial aspect of ZnTe/In2Te3 heterostructures as an efficient catalyst for the hydrogen evolution reaction 2019 Ingår i: Journal of Materials Chemistry A. - : Royal Society of Chemistry. - 2050-7488 .- 2050-7496. ; 7:48, s. 27441-27449 Tidskriftsartikel (refereegranskat)abstract In the class of two-dimensional (2D) materials, group III2-VI3 compounds have drawn intense attention due to its excellent surface properties. In this work, based on first-principles calculations, we have systematically investigated the structural, electronic, optical and photocatalytic properties of a ZnTe/In2Te3 heterostructure, along with its interfacial effects, to design an efficient photocatalyst. We have employed hydrogen adsorption free energy (Delta G(H*)) as a key parameter to demonstrate the enhancement in photocatalytic activity of ZnTe/In2Te3 compared to a pristine In2Te3 monolayer, which is further verified with the explicit water environment. The underlying mechanism is governed by the partial charge distributions of pristine In2Te3 and ZnTe/In2Te3 heterostructures. The presence of the ZnTe monolayer also altered the bandgap of the In2Te3 monolayer from an indirect gap of 1.238 eV to direct gaps of 0.298 eV and 0.181 eV in A- and B-type interfaces of the ZnTe/In2Te3 heterostructure, respectively. Calculated optical absorption spectra indicate that ZnTe/In2Te3 heterostructures possess better sunlight-harvesting capability compared to monolayer In2Te3 near the infrared and visible light regions, implying their potential as an excellent light-absorber. Our predictions provide new guidance for designing 2D III2-VI3 heterostructures and expand the applications of these materials in photovoltaics, photocatalysts, and other nanodevices in the future.
24.	Yang, Xiaoyong, et al. (författare) Probing the active sites of newly predicted stable Janus scandium dichalcogenides for photocatalytic water-splitting 2019 Ingår i: Catalysis Science & Technology. - : ROYAL SOC CHEMISTRY. - 2044-4753 .- 2044-4761. ; 9:18, s. 4981-4989 Tidskriftsartikel (refereegranskat)abstract The Janus structures of transition metal dichalcogenides with intrinsic dipoles have recently drawn attention as efficient candidates in the class of non-precious metal photocatalysts for water splitting. Here, we have proposed Janus ScXY (X/Y = S, Se, or Te, X not equal Y) monolayers as promising catalysts for the hydrogen evolution reaction (HER). We have thoroughly investigated the structural stabilities of the ScXY monolayers, as a primary step to understand the splitting mechanism more accurately. It has been observed that Janus ScSSe and ScSeTe monolayers are dynamically, thermally and mechanically stable, whereas the ScSTe monolayer is dynamically unstable. Moreover, based on hybrid functional (HSE06) calculations, these stable ScSSe and ScSeTe monolayers are semiconductors with direct band gaps of 1.810 and 0.921 eV, respectively. Considering spin-orbit coupling on top of the HSE06 calculations results in an insignificant change in the band gaps. The steady optical responses of Janus ScSSe and ScSeTe, respectively, in the visible and near IR spectra demonstrate their photocatalytic activities in the respective regions. Interestingly, we have observed excellent performance shown by the ScSeTe monolayer, where both surfaces are catalytically active, and maintain close to thermoneutral conditions with near-zero adsorption free energy at different H* coverages. Comparatively, the ScSSe monolayer shows poor performance for the HER due to strong bonds with the adsorbed hydrogen. Also, it has been confirmed that even the application of +/- 2% strain on the ScSSe monolayer does not enhance its HER activity. Our theoretical predictions demonstrate that out of all the Janus ScXY monolayers studied here, ScSeTe is the most active catalyst for the HER to efficiently split water, which certainly could make it worth performing further experimental investigations.
25.	Yang, Xiaoyong, et al. (författare) Recent Advancements and Future Prospects in Ultrathin 2D Semiconductor-Based Photocatalysts for Water Splitting 2020 Ingår i: Catalysts. - : MDPI. - 2073-4344. ; 10:10 Forskningsöversikt (refereegranskat)abstract Ultrathin two-dimensional (2D) semiconductor-mediated photocatalysts have shown their compelling potential and have arguably received tremendous attention in photocatalysis because of their superior thickness-dependent physical, chemical, mechanical and optical properties. Although numerous comprehensions about 2D semiconductor photocatalysts have been amassed up to now, low cost efficiency, degradation, kinetics of charge transfer along with recycling are still the big challenges to realize a wide application of 2D semiconductor-based photocatalysis. At present, most photocatalysts still need rare or expensive noble metals to improve the photocatalytic activity, which inhibits their commercial-scale application extremely. Thus, developing less costly, earth-abundant semiconductor-based photocatalysts with efficient conversion of sunlight energy remains the primary challenge. In this review, it begins with a brief description of the general mechanism of overall photocatalytic water splitting. Then a concise overview of different types of 2D semiconductor-mediated photocatalysts is given to figure out the advantages and disadvantages for mentioned semiconductor-based photocatalysis, including the structural property and stability, synthesize method, electrochemical property and optical properties for H2/O2 production half reaction along with overall water splitting. Finally, we conclude this review with a perspective, marked on some remaining challenges and new directions of 2D semiconductor-mediated photocatalysts.
26.	Yang, Xiaoyong, et al. (författare) Sensing the polar molecules MH3 (M = N, P, or As) with a Janus NbTeSe monolayer 2020 Ingår i: New Journal of Chemistry. - : Royal Society of Chemistry (RSC). - 1144-0546 .- 1369-9261. ; 44:19, s. 7932-7940 Tidskriftsartikel (refereegranskat)abstract The unique intrinsic electric field and prominent physical and chemical properties of Janus TMDs have attracted extensive attention for device applications. In this work, the performance of a Janus NbTeSe monolayer as a gas sensor is systematically investigated towards (N, P, and As)H-3 molecules combining first-principles calculations and non-equilibrium Green's function formalism. The adsorption energies and configurations of the molecules on different sites of the Janus NbTeSe are determined. It is found AsH3 exhibits a stronger interaction with the substrate than NH3 and PH3, implying Janus NbTeSe is more sensitive towards AsH3. Besides, the visible difference of adsorption energies for the molecules on two sides shows the selectivity of the NbTeSe monolayer. Notably, the interaction between the molecules and the substrate becomes weaker under strain-driven, indicating the fast recovery and re-utilization of NbTeSe as a gas sensor device. Importantly, Janus NbTeSe exhibits a high anisotropic transport behavior; the modification of I-V responses correspondingly shows a surface-dependent trend. With higher gas sensitivity, surface selectivity and strain-driven desorption property, NbTeSe monolayer is proposed as a compelling and feasible candidate for gas sensing devices.
27.	Yang, Xiaoyong, et al. (författare) Strain engineering of the electrocatalytic activity of nitrogen-rich BeN4 Dirac monolayer for hydrogen evolution reaction 2023 Ingår i: Nano Energy. - : ELSEVIER. - 2211-2855 .- 2211-3282. ; 113 Tidskriftsartikel (refereegranskat)abstract The strong bond energy and short bond length of N & EQUIV;N triple bond make it a challenging target for synthesizing nitrogen-rich compounds. However, recent research has successfully fabricated atomic-thick BeN4 layers under high pressure (Bykov et al., 2021). Beryllonitrene, a new 2D material, consists of a Be atom and polymeric nitrogen chains and has anisotropic Dirac cones located near the Fermi level. This distinguishes it from graphene, which has isotropic Dirac cones, bulk PtTe2 and 2D borophene, which have Dirac cones located far from the Fermi energy. The anisotropic Dirac cones in beryllonitrene result in ultrahigh carrier mobility and the potential for direction-dependent quantum devices. In this study, we systematically investigated the hydrogen evolution reaction (HER) catalytic activity of nitrogen-rich, non-precious BeN4 monolayer using first-principles DFT calculations. Our results demonstrate that BeN4 monolayer is thermally stable, and Be vacancy is the most energetically favorable site for hydrogen adsorption. We also found the Gibbs free energy (ΔGH) of H coverage can be turned to an optimal value of (ΔGH*) ≤0.2 eV through strain engineering, significantly enhancing the HER electrocatalytic activity of BeN4 monolayer. Furthermore, we examined both the homolytic Tafel reaction and heterolytic Heyrovsky reaction for HER mechanism using reaction kinetics and AIMD simulations. These findings can contribute to the development of high-performance, non-precious, and nitrogen-rich 2D catalysts for HER in future research.
28.	Yang, Xiaoyong, et al. (författare) Unveiling the energetic and structural properties of Pu doped zircon through electrochemical equilibrium diagram from DFT plus U calculations 2020 Ingår i: Journal of Nuclear Materials. - : Elsevier BV. - 0022-3115 .- 1873-4820. ; 539 Tidskriftsartikel (refereegranskat)abstract Zircon (ZrSiO4) mineral is a sustainable and promising material to store of radioactive waste that has received extensive attention by material, geochemical and environmental scientists. Although the incorporation of actinide elements in zircon lattices has been experimentally studied, bare fundamental work are carried out to systemically assess the structural and chemical stabilities of Pu doped zircon. The primary aim to unveil the Pu immobilization mechanism and assess the stability of PuxZr1-xSiO4 is carried out by calculating the formation energies, electron and hole affinities, and electronic levels of Pu doped zircon based on density functional theory. Our results reveal under mu = mu(O-poor) condition Pu-Si(4+), Pu-Zr(1+) and Pu-Zr(0) are respectively energetically favorable to form with increasing the electronic chemical potential. Besides, Pu-Zr(4+) is energetically favorable in an n-type environment under all these three conditions (i.e., mu = mu(O-poor), mu = mu(Pu/Zr), mu = mu(Pu/Si)). In addition, Pu doping will induce local structural distortion. Intriguingly however, self-repairing the symmetry of [ZrO8] polyhedra is first observed via the structural distortion in Pu-Zr(4+) configuration, which in turn could enhance the structural stability of PuxZr1-xSiO4. Ab initio molecular dynamic simulations demonstrate the configurations with negative formation energies are thermal stable at 500 K. The charge density difference and charge transfer are investigated to describe the chemical bonding nature. It is demonstrated Pu(5f)-O(2p) hybridization is more profound for interstitial Pu. Moreover, the bonding character of surrounding Zr atoms along [010] direction is almost identical to the pristine one, while it is distinctly changed towards [100] and [001] directions, showing remarkable anisotropy of PuxZr1-xSiO4. Oppositely, the ionicity in Pu-O bond is mainly featured when Zr or Si sites are substituted by Pu atoms which becomes stronger with increasing the hole doping process. (C) 2020 Elsevier B.V. All rights reserved.
29.	Ye, Tong, et al. (författare) Synthesis of Rhenium-Doped Copper Twin Boundary for High-Turnover-Frequency Electrochemical Nitrogen Reduction 2024 Ingår i: ACS Applied Materials and Interfaces. - : American Chemical Society (ACS). - 1944-8244 .- 1944-8252. ; 16:19, s. 24580-24589 Tidskriftsartikel (refereegranskat)abstract The precise design and synthesis of active sites to improve catalyst's performance has emerged as a promising tactic for electrochemistry. However, it is challenging to combine different types of active sites and manipulate them simultaneously at atomic resolution. Here, we present a strategy to synthesize Re atom-doped Cu twin boundaries (TBs), through pulsed electrodeposition and boundary segregation. The Re-doped Cu TBs demonstrate a highly efficient nitrogen reduction reaction (NRR) performance. Re-doped Cu TBs showed a turnover frequency of ∼5889 s-1, ∼800 times higher than the pure Cu TB active centers (∼7 s-1). In addition to the "acceptance-donation" activation of N2 molecules, theoretical calculations also reveal that the Re-Re dimer on TB can boost the NRR and impede the hydrogen evolution reaction synchronously, rendering Re-doped Cu TB catalysts with high NRR activity and selectivity.
30.	Ye, Tong, et al. (författare) Valence engineering at the interface of MoS2/Mo2C heterostructure for bionic nitrogen reduction 2023 Ingår i: Chemical Engineering Journal. - : Elsevier BV. - 1385-8947 .- 1873-3212. ; 452 Tidskriftsartikel (refereegranskat)abstract The natural nitrogenase is still the most efficient catalyst on earth to reduce the ambient N2 into ammonia. The central part of the molecular machine is powered by a metallic core, usually a molybdenum atom, whose co-ordination valence state remains an enigma for us to unveil and mimic. Unlike the flexible bio-enzyme, inorganic heterogeneous catalysts are usually rigid in the coordination structure, making their valence states invariable, except some localized defects. In this study, we successfully synthesized a two-dimensional MoS2/Mo2C elec-trocatalyst, which contains a heterostructured interface with efficient charge and magnetism separation, exhibiting a gradual and broad valence state transition from Mo4+ to Mo2+. Density functional theory (DFT) calculations reveal that Mo3+ sites at the interface have a strong N2 adsorption energy of -0.75 eV with the side -on configuration, and an activated hydrogenation of *NH2 species. This bionic electrocatalyst displays a splendid performance in nitrogen reduction reaction with a Faradic efficiency of 42 % at-0.1 V vs RHE.
31.	Yuan, Chunyu, et al. (författare) Defect and Donor Manipulated Highly Efficient Electron-Hole Separation in a 3D Nanoporous Schottky Heterojunction 2023 Ingår i: JACS Au. - : American Chemical Society (ACS). - 2691-3704. ; 3:11, s. 3127-3140 Tidskriftsartikel (refereegranskat)abstract Given the rapid recombination of photogenerated charge carriers and photocorrosion, transition metal sulfide photocatalysts usually suffer from modest photocatalytic performance. Herein, S-vacancy-rich ZnIn2S4 (VS-ZIS) nanosheets are integrated on 3D bicontinuous nitrogen-doped nanoporous graphene (N-npG), forming 3D heterostructures with well-fitted geometric configuration (VS-ZIS/N-npG) for highly efficient photocatalytic hydrogen production. The VS-ZIS/N-npG presents ultrafast interfacial photogenerated electrons captured by the S vacancies in VS-ZIS and holes neutralization behaviors by the extra free electrons in N-npG during photocatalysis, which are demonstrated by in situ XPS, femtosecond transient absorption (fs-TA) spectroscopy, and transient-state surface photovoltage (TS-SPV) spectra. The simulated interfacial charge rearrangement behaviors from DFT calculations also verify the separation tendency of photogenerated charge carriers. Thus, the optimized VS-ZIS/N-npG 3D hierarchical heterojunction with 1.0 wt % N-npG exhibits a comparably high hydrogen generation rate of 4222.4 μmol g–1 h–1, which is 5.6-fold higher than the bare VS-ZIS and 12.7-fold higher than the ZIS without S vacancies. This work sheds light on the rational design of photogenerated carrier transfer paths to facilitate charge separation and provides further hints for the design of hierarchical heterostructure photocatalysts.
32.	Zhang, Kaiyue, et al. (författare) Regulated Surface Electronic States of CuNi Nanoparticles through Metal-Support Interaction for Enhanced Electrocatalytic CO2 Reduction to Ethanol 2023 Ingår i: Small. - : Wiley. - 1613-6810 .- 1613-6829. ; 19:32 Tidskriftsartikel (refereegranskat)abstract Developing stable catalysts with higher selectivity and activity within a wide potential range is critical for efficiently converting CO2 to ethanol. Here, the carbon-encapsulated CuNi nanoparticles anchored on nitrogen-doped nanoporous graphene (CuNi@C/N-npG) composite are designedly prepared and display the excellent CO2 reduction performance with the higher ethanol Faradaic effiency (FEethanol ≥ 60%) in a wide potential window (600 mV). The optimal cathodic energy efficiency (47.6%), Faradaic efficiency (84%), and selectivity (96.6%) are also obtained at −0.78 V versus reversible hydrogen electrode (RHE). Combining with the density functional theory (DFT) calculations, it is demonstrated that the stronger metal-support interaction (Ni-N-C) can regulate the surface electronic structure effectively, boosting the electron transfer and stabilizing the active sites (Cu0-Cuδ+) on the surface of CuNi@C/N-npG, finally realizing the controllable transition of reaction intermediates. This work may guide the designs of electrocatalysts with highly catalytic performance for CO2 reduction to C2+ products.
33.	Zhao, XiaoFeng, et al. (författare) 2D g-C3N4 monolayer for amino acids sequencing 2020 Ingår i: Applied Surface Science. - : Elsevier BV. - 0169-4332 .- 1873-5584. ; 528 Tidskriftsartikel (refereegranskat)abstract An analog of graphene, graphitic carbon nitride (g-C3N4), is a promising metal-free conjugated polymer, owing to its excellent performance in biosensing and photocatalysis. We have demonstrated the adsorption of twenty-five amino acids (AA) employing DFT-D3 correction method of Grimme's dispersion and the non-equilibrium Green's function (NEGF) for describing the coherent transport in molecular devices coupled with adsorption energies, substrate-adsorbate distances, the density of states, charge transfer mechanism, molecular dynamics, work function, and bonding patterns. We have also depicted the current-voltage (I-V) characteristics where the curves of current vs. bias voltage (I-V-b) display a distinct response for each AA. Furthermore, we have illustrated the anti-bacterial mechanism of g-C3N4 utilizing bioinformatics study and compared it with DFT studies. We found evidence of a difference in transport, electronic as well as molecular mechanisms reinforcing the possibility of g-C3N4 applications based on sensors for AA sequencing of proteins, water-disinfection technique, and microbial control.
34.	Zhao, XiaoFeng, et al. (författare) Exploring the Degradation Behavior of Ce-Monazite in Water Solution through Adsorption and Penetration Kinetics 2020 Ingår i: The Journal of Physical Chemistry C. - : American Chemical Society (ACS). - 1932-7447 .- 1932-7455. ; 124:40, s. 22173-22184 Tidskriftsartikel (refereegranskat)abstract Monazite (LnPO(4), Ln = La-Gd) is an important light lanthanide phosphate for the application of ionic conductors, coatings, and diffusion barriers and the safe disposal of high-level radioactive wastes, and thus evaluating its chemical durability is critical. However, the degradation mechanism of monazite upon a water solution has not yet been fully established. In this work, the effects of water on the detailed structure and properties of CePO4 monazite are systematically investigated based on density functional theory. Some specific issues such as surface hydrolysis reaction and the nucleation of rhabdophane precipitation are discussed in detail and compared with the available dissolution experimental results. The results reveal that the interaction between water molecules and the (010) surface is dominated by the physisorption of the Ce atoms rather than [PO4] tetrahedron. The bilayer water with 16 H2O molecules can describe the fundamental forces at the water-monazite interface associated with water-solid interaction and water-water interaction. The penetrating water molecules play a key role in corroding down the whole (010) surface to form the Schottky defect pairs of Ce and [PO4]. Importantly, these dissolved ions are easily adsorbed on the defective area of the (010) surface, which contributes to the nucleation of CePO4 center dot 0.667H(2)O rhabdophane precipitation. Moreover, some potential diffusion pathways for the H2O molecule to migrate on the surface and penetrate into the inner (010) matrix are discussed.
35.	Zhao, Xiaofeng, et al. (författare) Strain-Engineered Metal-Free h-B2O Monolayer as a Mechanocatalyst for Photocatalysis and Improved Hydrogen Evolution Reaction 2020 Ingår i: The Journal of Physical Chemistry C. - : AMER CHEMICAL SOC. - 1932-7447 .- 1932-7455. ; 124:14, s. 7884-7892 Tidskriftsartikel (refereegranskat)abstract Developing stable metal-free materials with a highly efficient hydrogen evolution reaction (HER) has received intense research interest due to its renewable and environmentally friendly properties. In this work, we systematically investigated the HER catalytic activity of a new h-B2O monolayer based on first-principles calculations. The results show the B site in the h-B2O structure is energetically favorable for hydrogen with the calculated Gibbs free energy (Delta G(H)) of -0.07 eV, which is comparable to that of the Pt catalyst (Delta G(H)) = -0.09 eV). Moreover, the catalytic activity of the h-B2O monolayer is quite robust with increasing hydrogen coverages (from 1/9 to 9/9). Interestingly, the HER activity of the h-B2O monolayer is sensitive to the strains-driven. For example, applied tensile strains (0-2%) could weaken the bonding between hydrogen and the substrate, resulting in Delta G(H*) even close to 0 eV. However, the opposite trend is found for applied compressive strain. After analyzing the density of states (DOS), we found the h-B2O monolayer with absorbed hydrogen retains the metallic property, still exhibiting excellent electrical conductivity. These results reveal that the metal-free h-B2O monolayer is a promising candidate for HER applications.

Skapa referenser, mejla, bekava och länka

Länka till träfflistan

Träfflista för sökning "WFRF:(Yang Xiaoyong) "

Avgränsa träffmängd

År