Abstract:With a first-principles method based on density functional theory, the effect of the alloying element titanium ( Ti ) on the thermodynamic stability and electronic structure of hydrogen ( H ) in pure vanadium ( V ) is investigated. The interactions between H and the vacancy and the defect solution energies in a dilute V – Ti binary alloy are calculated. The results show that: (i) a single H atom prefers to reside in a tetrahedral interstitial site in dilute V – Ti binary alloy systems; (ii) H atoms tend to bon… Show more
“…To quantify the change in charge density, we also employed Bader charge analysis, which showed that the H atoms at the TS, BS, and HS have 0.4757, 0.5507, and 0.5965 e, respectively. As far as we know, more negatively charged H atoms have lower energies [20]. This is why the H atom is adsorbed more stably at the TS than at the other sites.Fig.…”
Section: Resultsmentioning
confidence: 88%
“…To our knowledge, preparing clean V surfaces for experiments is difficult and time-consuming [6], [17], [18]. Studies in the literature that theoretically calculate the H behaviour on V surfaces are limited, despite the interactions between atoms or molecules and solid surfaces being of interest to several industries, especially in heterogeneous catalysis, gas corrosion, separation, and crystal growth [19], [20], [21], [22]. Therefore, to provide further insight into the mechanism of H and metal interaction, the mechanisms of H permeation processes have been investigated in detail for metallic membranes.…”
“…To quantify the change in charge density, we also employed Bader charge analysis, which showed that the H atoms at the TS, BS, and HS have 0.4757, 0.5507, and 0.5965 e, respectively. As far as we know, more negatively charged H atoms have lower energies [20]. This is why the H atom is adsorbed more stably at the TS than at the other sites.Fig.…”
Section: Resultsmentioning
confidence: 88%
“…To our knowledge, preparing clean V surfaces for experiments is difficult and time-consuming [6], [17], [18]. Studies in the literature that theoretically calculate the H behaviour on V surfaces are limited, despite the interactions between atoms or molecules and solid surfaces being of interest to several industries, especially in heterogeneous catalysis, gas corrosion, separation, and crystal growth [19], [20], [21], [22]. Therefore, to provide further insight into the mechanism of H and metal interaction, the mechanisms of H permeation processes have been investigated in detail for metallic membranes.…”
“…They found that doping Ti into dilute V−Ti binary alloys inhibits the H solution and thereby suppresses hydrogen retention. 34 Ma et al examined the adsorption properties and mechanism of hydrogen molecules on Ti-decorated carbon-based hydrogen adsorbent structures using DFT calculations. According to the findings, Ti-decorated graphene appears to be a good material for hydrogen storage.…”
Section: Introductionmentioning
confidence: 99%
“…Hua et al calculated the interactions between H and the vacancy and defect solution energies as well as the contributions of Ti to stability in a dilute V–Ti binary alloy as a candidate structural material in fusion reactors. They found that doping Ti into dilute V–Ti binary alloys inhibits the H solution and thereby suppresses hydrogen retention . Ma et al examined the adsorption properties and mechanism of hydrogen molecules on Ti-decorated carbon-based hydrogen adsorbent structures using DFT calculations.…”
The effects of alloying and hydrogen dissolution on the mechanical, thermal, and electrical properties of vanadiumbased ternary alloys were investigated using density functional theory. Our study showed that pure V has a lower solution energy than V−Ti−X alloys. Also, tetrahedral interstitial sites are more favorable than octahedral sites to be occupied by the H atoms. Furthermore, the alloys with eight H atoms have a lower capacity than the pure V system for H-trapping at interstitial sites. These findings suggest that H-dissolution in alloys is less probable than in pure V, and the alloys are more resistant to hydrogen embrittlement, crack propagation, and fracture initiation. Indeed, V−Ti−Al shows a reliable performance and could be a viable non-Pd alloy for hydrogen separation. Studying the mechanical properties of pure V and the ternary alloys revealed that V−Ti−Ni provides the highest durability and better resistance to both external and hydrogen dissolution-induced internal stresses. The V−Ti−Pd alloy has a higher diffusion barrier energy (E b = 0.1807 eV) than pure V (E b = 0.1646 eV), indicating that the H atom faces more hindrance when it diffuses across the alloy. Nonetheless, in the hydrogen separation temperature range, the V−Ti−Pd alloy has the largest thermal expansion coefficient (α = 2.048×10 −5 K −1 ), which indicates its poor thermal characteristics. Altogether, the superior mechanical properties of the V−Ti−Ni alloy indicate that it will be resistant to deformation and have a long service life in hydrogen separation applications. The V−Ti−Ni alloy has a higher heat capacity than the others, which is important in exothermic processes like hydrogen separation.
“…With development of technology, there are increasing kinds of photocatalysts, including various oxides, sulfides, oxynitride semiconductors, etc. [4][5][6][7][8][9][10][11][12], which belong to inorganic materials. Inorganic photocatalysts materials have some drawbacks, for example limited concentration of active sites and heavy metal toxicity [13][14][15].…”
It is of practical significance to find organic metal-free catalyst materials. We propose a new graphene-like carbon nitride structure, which was able to meet these requirements well. Its primitive cell consists of eight carbon atoms and six nitrogen atoms. Hence, we called this structure g–C8N6. The stability of the structure was verified by phonon spectroscopy and molecular dynamics simulations. Then its electronic structure was calculated, and its band edge position was compared with the redox potential of water. We analyzed its optical properties and electron–hole recombination rate. After the above analysis, it is predicted that it is a suitable photocatalyst material. To improve its photocatalytic performance, two methods were proposed: applied tensile force and multilayer stacking. Our research is instructive for the photocatalytic application of this kind of materials.
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