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Aqueous aluminum-ion batteries (AIBs) are potential candidates for future large-scale energy storage devices owing to their advantages of high energy density, resource abundance, low cost, and environmental friendliness. However, the exploration of suitable electrode materials is one of the key challenges for the development of aqueous AIBs. To address this issue, a new Ti-deficient rutile titanium dioxide (Ti0.95□0.05O1.79Cl0.08(OH)0.13) was achieved via univalent ion doping and evaluated as an anode for aqueous AIBs. This material yields a reversible capacity of 143.1 mA h g−1 at 0.5 A g−1. Even at 3 A g−1, an initial reversible charge capacity of 78.3 mA h g−1 can be achieved and retains almost 82% after 110 cycles. The Al3+ ion storage mechanism has been intensively investigated by ex-situ XRD, XPS, SEM, TEM and Raman techniques, indicating that Al3+ ions can reversibly insert into Ti vacancies and lattice of the Ti0.95□0.05O1.79Cl0.08(OH)0.13 without phase change, leading to much enhanced capacity as compared to the commercial rutile TiO2. These results demonstrate that cationic defect engineering is an effective strategy to improve the electrochemical properties of electrode materials for aqueous AIBs.

Graphical abstract Schematic of H permeation of dense metallic membrane., Highlights • Interaction between H and V surface and bulk are fully studied. • H coverage (θ) effects the adsorption energy of H/V(1 0 0). • H solubility and diffusivity depend slightly on the H concentration., To investigate the H2 purification mechanism of V membranes, we studied the adsorption, dissociation, and diffusion properties of H in V, an attractive candidate for H2 separation materials. Our results revealed that the most stable site on the V (1 0 0) surface is the hollow site (HS) for both adsorbed H atoms and molecules. As the coverage range increases, the adsorption energy of H2 molecules first decreases and then increases, while that of H atoms remains unchanged. The preferred diffusion path of atoms on the surface, surface to first subsurface, and first subsurface to second subsurface is HS → bridge site (BS) → HS, BS → BS, and BS → tetrahedral interstitial site (TIS) → BS, respectively. In the V bulk, H atoms occupy the energetically favourable TIS, and diffuse along the TIS → TIS path, which has a lower energy barrier. This study facilitates the understanding of the interaction between H and metals and the design of novel V-based alloy membranes.

The group VB metals (V, Nb, Ta) are referred to as one of the most valuable hydrogen separation membrane materials because of their advantages over Pd. To evaluate the hydrogen-permeation performance of the three metals, their structure stability, H-solubility, H-diffusivity, H-permeability, and elastic stiffness tensors have been investigated using the first-principles method. Our results reveal that the tetrahedral interstitial site (TIS) is favorable position for H-occupying, but mainly because H-solution enthalpy is the lowest. H-diffusion coefficient follows the order of V > Nb > Ta, H-permeability and H-permeation flux follow the order of Nb > V > Ta. The attractive interactions between H atoms are weak, so it is impossible to form H2 molecules inside the metals, and all metal hydride phases present good ductility. The calculated Debye temperature is basically consistent with the experimental value. These results provide fundamental data for the further design of alloy membranes based on VB metals.

Vanadium-based materials are considered ideal for hydrogen separation membranes owing to their higher hydrogen permeability and mechanical strength and lower cost compared with other widely used materials such as Pd alloys. However, pure V exhibits severe hydrogen embrittlement, which is often solved by alloying. In the present study, we used first-principles method to systematically calculate the hydrogen solubility, diffusivity, and other mechanical properties of different V-based binary alloys, namely, V–Co, V–Mo, V–Pd, V–Ru, and V–W. The alloys were found to possess stable crystal structures, and on exposure to hydrogen, the H atoms preferentially occupied the tetrahedral interstitial sites (TISs) in both the pure V and alloy within the material matrix, preferentially diffusing between TISs. The hydrogen diffusion coefficients of the different alloys decreased in the order V–Pd > V–Co > V–Ru > V–Mo > V–W. The alloys and their hydrides also exhibited good mechanical properties, with their resistances to hydrogen embrittlement decreasing in the order V–Co > V–Ru > V–Pd > V–Mo > V–W. This revealed that the resistance to hydrogen embrittlement of the alloy increased with decreasing atomic size of the alloying element. The findings of this study promise to facilitate the development of novel V-alloy membranes for hydrogen separation and purification.

The dietary lead (Pb) risk across China was assessed based on the margin of exposure (MOE) approach by comparing the level (1.5 μg/kg/d) based on the Pb concentrations in foodstuffs from1386 published articles. The Pb averages of the 18 foods were lower than their corresponding limits enacted by the Chinese government, ranging from 0.09 to 0.30 mg/kg. Food from plants had a much higher contribution to dietary Pb intake than that from animals (86% vs. 14%), and cereals and vegetables contributed 79% of the Pb intake from plant-based food. Although each category of food contained a relatively low Pb concentration, the accumulated Pb from the total diet posed a high risk to human health. The MOE risk from dietary Pb averaged 1.57 and ranged from 0.13 to 6.18, with high risks in southern, southwestern, eastern, central, and northern China. The MOE risk from Pb could be decreased by adjusting the dietary structure, and the ratio of people categorized as high risk (MOE < 1) would decrease from 56% to 37%, 41%, or 24% if the category of cereal or vegetable or both cereals and vegetables with the lowest Pb concentration in their local areas were selected, respectively.

Hydrogen embrittlement causes deterioration of materials used in hydrogen energy systems. Alloying is an effective means for overcoming this issue. In this study, the first-principles calculation method was used to investigate the effects of alloying Ni on the stability, dissolution, trapping, and diffusion behaviour of interstitial/vacancy H atoms in V. The calculated phonon spectra and solution energies of the vacancy/interstitial H atoms revealed that the V–Ni phase was dynamically and thermodynamically stable, and Ni addition could reduce the stability of V hydrides and improve their resistance to H embrittlement. H atoms in the interstitials and vacancies preferentially occupied the tetrahedral interstitial site (TIS) and octahedral interstitial site (OIS) with the lowest solution energies and diffused along the TIS → TIS and OIS → OIS paths with the minimum diffusion barrier energies. The trapping energy of the vacancy H atoms indicated that the addition of Ni could reduce the H trapping capability of the vacancies and suppress the retention of H in V. Detailed analysis of the calculated H diffusion barriers indicated that the presence of monovacancy defects blocked the diffusion of H atoms more than the presence of interstitials, and Ni doping did not enhance the H diffusion coefficient.

To improve the resistance to hydrogen embrittlement and hydrogen permeation performance of vanadium (V) membranes, first-principles calculations were employed to study the stability, dissolution, and diffusion properties of H in transition metal (M = Mo, W)-doped V membranes, as well as their mechanical and thermodynamic properties, as alternative candidates for H2 separation. Our results revealed that the doping percentage of Mo/W alloying can significantly improve the mechanical and thermodynamic properties of pure V. The most stable location for adsorbed H atoms is the tetrahedral interstitial site (TIS) in the body-centered cubic structure of the V1-xMx (x = 0.0625, 0.125, 0.1875, and 0.25) alloys. Additionally, the hydrogen migration path should preferentially follow TIS → nearest-neighbor TIS. An M content of 0.25 yields the best anti-hydrogen embrittlement and the highest hydrogen-diffusion properties. The addition of individual Mo or W as doping elements into the V-based system greatly enhanced the hydrogen diffusion coefficient, and the addition of both Mo and W significantly improved the anti-hydrogen embrittlement of V-based alloys. Our results also showed that hydrogen concentration markedly influenced the solubility and diffusivity of hydrogen in V-based alloy membranes. These results provide a basis for the design of V-based alloy hydrogen permeation membranes.

To investigate Mo doping effects on the hydrogen permeation performance of Nb membranes, we study the most likely process of atomic hydrogen adsorption and diffusion on/into Mo-doped Nb (100) surface/subsurface (in the Nb12Mo4 case) via first-principles calculations. Our results reveal that the (100) surface is the most stable Mo-doped Nb surface with the smallest surface energy (2.75 J/m2). Hollow sites (HSs) in the Mo-doped Nb (100) surface are H-adsorption-favorable mainly due to their large adsorption energy (&minus, 4.27 eV), and the H-diffusion path should preferentially be HS&rarr, TIS (tetrahedral interstitial site) over HS&rarr, OIS (octahedral interstitial site) because of the correspondingly lower H-diffusion energy barrier. With respect to a pure Nb (100) surface, the Mo-doped Nb (100) surface has a smaller energy barrier along the HS&rarr, TIS pathway (0.31 eV).