Cation-exchange method is developed to synthesize vertically aligned NiS/SnS2 porous nanowalls for aqueous battery–supercapacitor hybrid devices with ultrahigh specific capacity.
We have studied the dynamic relationship between acetone and bridge-bonded oxygen (Ob) vacancy (VO) defect sites on the TiO2(110)-1 × 1 surface using scanning tunneling microscopy (STM) and density function theory (DFT) calculations. We report an adsorbate-assisted VO diffusion mechanism. The STM images taken at 300 K show that acetone preferably adsorbs on the VO site and is mobile. The sequential isothermal STM images directly show that the mobile acetone effectively migrates the position of VO by a combination of two acetone diffusion channels: one is the diffusion along the Ob row and moving as an alkyl group, which heals the initial VO; another is the diffusion from the Ob row to the five-coordinated Ti(4+) row and then moving along the Ti(4+) row as an acetone, which leaves a VO behind. The calculated acetone diffusion barriers for the two channels are comparable and agree with experimental results.
Exploring materials with high hydrogen evolution reaction (HER) performance is of importance for the development of clean hydrogen energy, and the defects on the surfaces of catalysts are essential. In this work, we evaluate the HER performance among group IVA monochalcogenides MXs (M = Ge/Sn, X = S/Se) with M/X point defects on the edges. Compared with basal planes and bare edges, the GeS edge with Ge vacancy (ΔG H* = 0.016 eV), GeSe edge with Se vacancy (ΔG H* = 0.073 eV), and SnSe edge with Sn vacancy (ΔG H* = −0.037 eV) hold the best HER performances, which are comparable to or even better than the value for Pt (−0.07 eV). Furthermore, the relationships between ΔG H* and p-band centers of considered models are summarized. The stability of proposed electrocatalysts are analyzed by vacancy-formation energy and strain engineering. In summary, the HER performance of MXs is greatly improved by introduction of point defects at the edges, which is promising for their use as electrocatalysts for the conversion and storage of energy in the future.
Lithium iron phosphate (LiFePO4) has been widely used due to its high theoretical capacity and good cycle stability, but lithium manganese phosphate (LiMnPO4) with a higher operating voltage (4.1 V) has not been used, so it is necessary to conduct theoretical research on its inherent performance improvement strategy. The large‐scale application of LiMnPO4 is limited by its relatively low electronic and ionic conductivity. Improving the electronic and ionic conductivity of electrode materials by selective doping is an effective strategy. To determine the effect of doping of transition metals on the electrochemical properties of LiMnPO4 and to screen out doping models of cathode materials with excellent battery performance, we established all 3d, 4d, and 5d transition‐metal doping models of LiMnPO4. Through screening by first principles, the structural properties, band gap, doping formation energy, elastic properties, isotropy, and lithium/delithium voltage of the above models were compared and analyzed. According to the screening results, LiMnPO4 doped with Sc, Ti, V, Fe, Co, Mo, Rh, Re, and Ir has excellent electrochemical properties and can be used as a good cathode material for lithium‐ion batteries; the inherent mechanism of the above materials is revealed.
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