In this work, the uniform B2WO6-reduced graphene oxide (BWO–RGO) nanocomposites are prepared via electrostatic self-assembly of positively charged BWO with negatively charged GO sheets and then the composited GO is reduced via the hydrothermal treatment. The close interfacial contact and strong electronic interaction between BWO and RGO are achieved by this facile and efficient self-assembly route. Photocatalytic degradation of pollutant bisphenol A, selective oxidation of benzyl alcohol, removal of heavy metal ion Cr(VI), and selective reduction of 4-nitrophenol are selected as the probe reactions to investigate the photocatalytic activities of as-obtained BWO–RGO nanocomposites. The experimental results demonstrate the photocatalytic redox activities of BWO–RGO composites are predominantly dependent on the energy levels of photoinduced electrons or holes. In particular, the upshift of the valence band and conduction band edge of catalysts induced by the electronic interaction between BWO and RGO has an inconsistent influence on the photocatalytic reduction and oxidation reactions, respectively. As a result, the photocatalytic activity of reduction reactions is significantly enhanced, owing to the synergetic effect of the upshift of conduction band edge and the improved separation of photogenerated electrons/holes, while the oxidation ability of BWO–RGO nanocomposite is improved to a slight extent compared with bare BWO. The energy levels of photogenerated carriers should be the origins accounting for the different enhancement of photocatalytic activities for the different reactions. According to the discussion, one important conclusion can be drawn, that is, the results should be analyzed on the basis of specific reactions when discussing the effect of graphene or RGO on the photocatalytic properties of semiconductor particles.

Hexagonal boron nitride (h-BN) is crucial for many applications, and its synthesis over a large area with high quality is strongly desired. A promising approach to synthesize h-BN is chemical vapor deposition on transition metal catalysts, in which the alignments of BN clusters in the initial growth determine both the types and the amounts of defects in h-BN. In the search for a better catalyst, we systematically studied the interactions between h-BN clusters and various metal surfaces. Our results show that the clusters on nearly all catalyst surfaces, no matter whether the (111) facets of face-centered cubic (FCC) metals or the (0001) facets of hexagonal close packed (HCP) metals, have two local minima with opposite orientations. During the initial growth, h-BN clusters adopt the energy-favored sites, whose registry is well preserved upon further growth owing to the strong interaction between the edge atoms of h-BN and the underlying substrates. On FCC(111), the h-BN domains are always aligned in parallel orientations, while on HCP(0001) they are parallel on the same terrace and anti-parallel on neighboring terraces. Beyond this, on the (111) surfaces of Ir and Rh, the BN configuration is much more energy favorable than BN, where, the subscripts h, t, and f represent the adsorption sites, hcp, top and fcc, respectively. Thus, Ir(111) and Rh(111) might promote the growth of h-BN domains with the same alignments, which will greatly improve the quality of h-BN by reducing the possibility of formation of grain boundaries.

Ab initio calculations are performed to probe the hydrogen bonding, structural, and superconducting behaviors of HBr and HCl under high pressure. The calculated results show that the hydrogen bond symmetrization (Cmc2(1)-->Cmcm transition) of HBr and HCl occurs at 25 and 40 GPa, respectively, which can be attributed to the symmetry stretching A(1) mode softening. After hydrogen bond symmetrization, a pressure-induced soft transverse acoustic phonon mode of Cmcm phase is identified and a unique metallic phase with monoclinic structure of P2(1)/m (4 molecules/cell) for both compounds is revealed by ab initio phonon calculations. This phase preserves the symmetric hydrogen bond and is stable in the pressure range from 134 to 196 GPa for HBr and above 233 GPa for HCl, while HBr is predicted to decompose into Br(2)+H(2) above 196 GPa. Perturbative linear-response calculations predict that the phase P2(1)/m is a superconductor with T(c) of 27-34 K for HBr at 160 GPa and 9-14 K for HCl at 280 GPa.

Investigating a high-efficiency photoelectrochemical (PEC) system is an essential strategy to realize solar energy conversion, and the catalytic activity is mostly regulated by the intrinsic electronic structure. Here, we synthesize a ferromagnetic ZnFe 2 O 4 (ZFO) photoelectrode with an improved ferromagnetic property by introducing cation disorder and oxygen vacancies. Ferromagnetic ZnFe 2 O 4 with an improved ferromagnetic property enables significant enhancement of PEC performance simply by placement of a permanent magnet to provide the photoelectrode with a magnetic field. The improvement is assigned to electron spin polarization of the ferromagnetic ZFO photoelectrode regulated by the magnetic field. Because of the spin state loss of excited electrons, there are many photoinduced electrons in the same spin state as holes, which is unfavorable for their recombination during the light excitation process. The polarization also benefits the charge transfer based on the magnetoresistance effect. This work extends the strategy of enhancing the separation of photoinduced charges.

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An intriguing sandwich-like metallic phase of P21/m-Z AlH3(H2) with superconducting temperatures of 132–146 K at 250 GPa.