Single-atom catalysts provide an effective approach to reduce the amount of precious metals meanwhile maintain their catalytic activity. However, the sluggish activity of the catalysts for alkaline water dissociation has hampered advances in highly efficient hydrogen production. Herein, we develop a single-atom platinum immobilized NiO/Ni heterostructure (PtSA-NiO/Ni) as an alkaline hydrogen evolution catalyst. It is found that Pt single atom coupled with NiO/Ni heterostructure enables the tunable binding abilities of hydroxyl ions (OH*) and hydrogen (H*), which efficiently tailors the water dissociation energy and promotes the H* conversion for accelerating alkaline hydrogen evolution reaction. A further enhancement is achieved by constructing PtSA-NiO/Ni nanosheets on Ag nanowires to form a hierarchical three-dimensional morphology. Consequently, the fabricated PtSA-NiO/Ni catalyst displays high alkaline hydrogen evolution performances with a quite high mass activity of 20.6 A mg−1 for Pt at the overpotential of 100 mV, significantly outperforming the reported catalysts.

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In this study, a systematic approach was applied to the hydrothermal synthesis of Zn 2 SnO 4 (ZTO) nanocrystals to gain insight into the fundamental factors controlling phase composition, particle size, crystal morphology and photocatalytic activity. The influence of various operating conditions, such as reaction temperature, alkaline concentration, duration time, and additive surfactants on the treatment process were investigated. By combining the results of X-ray diffraction (XRD), electron microscopy (SEM/TEM/ED/HRTEM), Raman and FT-IR spectroscopy, a complete structural and morphological characterization of the products was performed. The results indicated that the phase transformation probably evolved via a "dissolution-recrystallization" mechanism and accompanying the "Ostwald ripening" process. Furthermore, a correlation between the photocatalytic activity in the UV photodegradation of MB solutions and the particle properties was established.

Nanocubic La2Sn2O7 photocatalysts with pyrochlore structure have been successfully synthesized by a one-pot hydrothermal method. The effects of alkaline concentration, reaction time, and hydrothermal temperature on the structures and morphologies of the resultant products were investigated. On the basis of characterization results from X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and selected area electron diffraction (SAED), a possible growth mechanism of the nanocubes under the hydrothermal conditions was proposed. The absorption spectra of as-prepared cubic La2Sn2O7 photocatalyst were determined by UV−vis spectrometer. Photocatalytic experiments showed that the La2Sn2O7 samples not only had a high activity for degradation of methyl orange, but also had the activity for generating H2 with a rate of 39 μmol/h under ultraviolet light irradiation.

A new type of three-dimensional (3D) NiO/ultrathin derived graphene (UDG) hybrid on commercial Ni foam (NF) for a binder-free pseudocapacitor electrode is presented. NiO nanoflakes are in situ grown by a chemical bath deposition (CBD) technique on the free-standing 3D UDG/NF scaffold, which is first prepared by a simple nanocasting process consisting of hydrothermal reaction and subsequent thermal transformation. The 3D UDG/NF scaffold with interconnected network affords a high conductivity due to the high graphitization degree and efficiently facilitates the electron transport to NiO. Moreover, the 3D NiO/UDG/NF hybrid allows for a thinner 3D active material layer under the same loading density, which could shorten the diffusion paths of ions. The NiO/UDG/NF hybrid is directly used as a binder-free supercapacitor electrode, which exhibited significantly improved supercapacitor performance compared to the bare CBD prepared NiO/NF electrode.

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Single-atom catalysts (SACs) have exhibited extraordinary catalytic performance due to the utmost atom utilization efficiency and unique electronic states by metal-support interaction. Rationally designing SACs at the atomic level by...

In contrast with recent claims that the Heyd-Scuseria-Ernzerhof (HSE) screened hybrid functional can provide a good description of the electronic and magnetic structures of VO 2 phases [Eyert, Phys. Rev. Lett. 107, 016401 (2011)], we show here that the HSE lowest-energy solutions for both the low-temperature monoclinic (M1) phase and the high-temperature rutile (R) phase, which are obtained upon inclusion of spin polarization, are at odds with experimental observations. For the M1 phase the ground state is (but should not be) magnetic, while the ground state of the R phase, which is also spin polarized, is not (but should be) metallic. The energy difference between the low-temperature and high-temperature phases has strong discrepancies with the experimental latent heat. The screened hybrid functional approach of Heyd, Scuseria, and Ernzerhof (HSE) has accumulated significant success in the description of structural and electronic properties of molecules and solids at a moderate computational cost. [1][2][3] It has been recently argued that density functional theory (DFT) calculations based on this functional are quite capable of describing the electronic and magnetic properties of the metallic and insulating phases of vanadium dioxide VO 2 . 4 In particular, it was shown there that HSE calculations are capable of producing the expected band gap in the electronic structure of the monoclinic phase, in contrast with other DFT approximations.5 This is exciting progress, because modeling the VO 2 phase transition with relatively inexpensive DFT methods (the alternative is many-body GW calculations or dynamic mean-field theory) 6-8 opens the door to a more active role of ab initio design in the development of applications such as "smart" thermochromic windows. 9When heated to ∼340 K, pure VO 2 exhibits a transition from a monoclinic (M1) semiconductor phase to a tetragonal, rutile-like, metallic phase (R). 10 The transition is first order, 11 and a latent heat of 44 meV per VO 2 formula unit has been measured by calorimetric methods. 12 Therefore it can be expected that accurate calculations yield a band gap for the M1 phase but not for the R phase, and that the calculated total energy per formula unit of the R phase is higher than that of the M1 phase. In order to compare the electronic structures and energies of the two phases, we have performed HSE calculations using the planewave DFT program VASP,13 first using non-spin-polarized calculations as in Ref. 4, and then using spin-polarized calculations in different magnetic configurations. Experimentally determined crystal structures were used in the calculations, 14 including four and two formula units for the M1 and R phases, respectively, without geometry relaxation. In order to ensure a reliable energy comparison between phases, precision parameters were chosen to achieve a convergence of 1 meV/atom in total energy. This required k-point grids of 5 × 5 × 5 and 6 × 6 × 9 for the M1 and R unit cells, respectively (the same grids were used for the non-local-exchange...