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In this article, a transmissive three-frequency linearly polarized (LP) wave to circularly polarized (CP) wave metasurface is designed using all-dielectric materials. The structure is composed of a cross-shaped bar resonator and a split circular ring resonator. Numerical simulations results show that when the LP wave is incident on the device, it will be converted into nearly perfect right-handed circularly polarized (RHCP), left-handed circularly polarized and RHCP waves at 2.2146, 2.2467 and 2.3144 THz. The distribution of the conduct current, electric field and magnetic field are investigated to explain the physical mechanism. And the influence of the structural parameters and different incident angles for the structure are also studied in the end. [ABSTRACT FROM AUTHOR]

Herein, rhombohedral self-doped KNbO3 (S-KN) nanorods were fabricated via a one pot, solvothermal method without using any surfactant. The presence of Nb4+ in S-KN greatly narrows its band gap and thus extends its photoresponse from UV to the visible light region. Moreover, S-KN/Nb4N5 nanorod heterostructures were obtained by nitriding S-KN nanorods for different times, which exhibited significantly enhanced photocatalytic activity for hydrogen production under visible light irradiation. The junction formed between S-KN and Nb4N5 and the Nb4+ self-doping of KN are supposed to be responsible for the enhanced photocatalytic activity of S-KN/Nb4N5. This study also paves the way for the synthesis of other similar photocatalysts. [ABSTRACT FROM AUTHOR]

Designing and preparing porous materials without using any templates is a challenge. Herein, single-nozzle electrospinning technology coupled with post pyrolysis is applied to prepare cobalt nanoparticles embedded in N-doped carbon nanofibers with a hierarchical pore structure (HP-Co-NCNFs). The resultant HP-Co-NCNFs have lengths up to several millimeters with an average diameter of 200 nm and possess abundant micro/meso/macropores on both the surface and within the fibers. Such a microstructure endows the surface area as high as 115 m2 g−1. When used as an electrocatalyst for the oxygen reduction reaction (ORR), the HP-Co-NCNFs exhibit outstanding electrochemical performance in terms of activity, methanol tolerance, and durability. The hierarchically porous structure and high surface area can effectively decrease the mass transport resistance and increase the exposed ORR active sites. The sufficient amount of exposed ORR active sites along with accessible transport channel and enhanced electrical conductivity may be responsible for the good electrocatalytic performance. [ABSTRACT FROM AUTHOR]

H2 evolution catalysis has drawn great consideration and effective separation and delivery of the photoelectrons are particularly crucial during the whole process. In this paper, we fabricate porous Cu–Cu2O–graphene nanocomposites via a simple reflux synthesis route, which possess porous structure and excellent catalytic performance for water splitting. With Cu species being added into Cu2O–graphene, the resultant catalyst exhibits improved activity for H2 evolution reaction as compared to Cu2O, Cu–Cu2O and Cu2O–graphene, indicating excellent catalytic performance and potential practical use. We attribute this performance to the synergistic effect of Cu component and graphene, which features: (i) a broader range of light absorption; (ii) faster electron transfer; and (iii) lower recombination possibility of photogenerated electrons and holes. We believe that the Cu species and graphene both contribute greatly to this catalysis process, in which Cu can cooperate with graphene support to extract electrons and pass them to the Pt cocatalyst to form a “two-way transfer” process. It is also believed that this strategy can be extended to other catalysts based on Cu–Cu2O–graphene composites. [ABSTRACT FROM AUTHOR]

A porous semiconductor photocatalyst, γ-In2Se3, was first synthesized by a two-step hydrothermal-calcining process. It was shown that the porous γ-In2Se3 tetragons have superior photocatalytic activity for water splitting over γ-In2Se3 nanoparticles and commercial counterparts, which might be attributed to the combined effect of stronger UV light absorption properties and a porous structure. [ABSTRACT FROM AUTHOR]