CoN_(x)C active sites-rich three-dimensional porous carbon nanofibers network derived from bacterial cellulose and bimetal-ZIFs as efficient multifunctional electrocatalyst for rechargeable Zn–air batteries

In this work, a CoNxC active sites-rich three-dimensional porous carbon nanofibers network derived from bacterial cellulose and bimetal-ZIFs is prepared via a nucleation growth strategy and a pyrolysis process.The material displays excellent electrocatalytic activity for the oxygen reduction reaction, reaching a high limiting diffusion current density of -7.8 mA cm^(-2), outperforming metal–organic frameworks derived multifunctional electrocatalysts, and oxygen evolution reaction and hydrogen evolution reaction with low overpotentials of 380 and 107 mV, respectively. When the electrochemical properties are further evaluated, the electrocatalyst as an air cathode for Zn-air batteries exhibits a high cycling stability for63 h as well as a maximum power density of 308 mW cm^(-2), which is better than those for most Zn-air batteries reported to date. In addition, a power density of 152 mW cm^(-2) is provided by the solid-state Zn-air batteries, and the cycling stability is outstanding for 24 h. The remarkable electrocatalytic properties are attributed to the synergistic effect of the 3 D porous carbon nanofibers network and abundant inserted CoNxC active sites, which enable the fast transmission of ions and mass and simultaneously provide a large contact area for the electrode/electrolyte.

Interpenetrating structure for efficient Sb_(2)Se_(3) nanorod array solar cells loaded with CuInSe_(2) QDs sensitizer

The strong anisotropic electrical properties of one-dimensional(1 D) nanostructure semiconductors,especially the anisotropic carrier transport, have a negative and significant influence on the performance of solar cells if the nanostructures have random orientation. Considering the advantages of nanorod solar cells in carrier transport, we have achieved growth of vertically aligned Sb_(2)Se_(3) nanorod array with highly(hk1) orientation on Cd S substrate, and constructed superstrate nanorod solar cells for the first time. The Sb_(2)Se_(3) nanorod array solar cells exhibit the more efficient and long-range carrier transport in vertical direction. Furthermore, in order to suppress interface recombination, a CuInSe_(2) quantum dots(QDs) sensitizer has been applied to fill the volume between the nanorods completely, thus forming an interpenetrating nanocomposite structure. The CuInSe_(2) QDs can harvest additional light by absorption of visible light and contribute photocurrent. Meantime, the QDs function as a hole transport material and thus reduce the dependence of lateral transport. Consequently, the interpenetrating nanocomposite CuInSe_(2) / Sb_(2)Se_(3) solar cells display a power conversion efficiency of 7.54% with significant enhancements in the short-circuit current density and open-circuit voltage over pure Sb_(2)Se_(3) nanorod cells. This is the highest efficiency for superstrate solar cells based on Sb_(2)Se_(3) nanorod arrays.

Three-Dimensional Hierarchical Ternary Nanostructures Bismuth/Polypyrrole/CNTs for High Performance Potassium-lon Battery Anodes

In recent years,the anode materials of bismuth(Bi)-based potassium ion batteries with high theoretical capacity and suitable potassium ion insertion potential have attracted extensive attention.However,due to the volume expansion of Bi,the performance of Bi-based anode materials is not ideal during potassium ion(de)intercalation.In order to solve these problems,we report a three-dimensional(3D)ternary bismuth nanoparticles/conductive polymers/carbon nanotubes(Bi/PPy/CNT)hybrid anode material for K-ion batteries.At a current density of 100 mA·g^(-1),its reversible capacity reaches 302 mAh·g^(-1) after 200 cycles,while it reaches 195.7 mAh·g^(-1) after 600 cycles at 1 A·g^(-1).Its excellent performance is attributed to the hydrogel network which provides a range of electron transport networks and high porosity.Carbon nanotubes are used as electron enhancers to reduce the volume expansion of Bi particles during the reaction.This study provides a prerequisite for expanding the application of 3D ternary materials.

Effects of Lorentz Breaking on the Accretion onto a Schwarzschild-like Black Hole

We formulate and solve the problem of spherically symmetric, steady state, adiabatic accretion onto a Schwarzschild-like black hole obtained recently. We derive the general analytic expressions for the critical points, the critical velocity, the critical speed of sound, and subsequently the mass accretion rate. The case for polytropic gas is discussed in detail. We find the parameter characterizing the breaking of Lorentz symmetry will slow down the mass accretion rate, while has no effect on the gas compression and the temperature profile below the critical radius and at the event horizon.

Corrections to R_D and R_(D~*) in the BLMSSM

The deviation of the measurement of RD(R_(D*)) from the Standard Model(SM) expectation is 2.3σ(3.1σ). RD(R_(D*)) is the ratio of the branching fraction of B→Dτντ(B→D*τντ) to that of B→Dlνl(B→D*lνl),where l =e or μ. This anomaly may imply the existence of new physics(NP). In this paper, we restudy this problem in the supersymmetric extension of the Standard Model with local gauged baryon and lepton numbers(BLMSSM),and give one-loop corrections to RD(R_(D*)).

Horizon thermodynamics in f(R,R^μνRμν)theory

We investigate whether the new horizon first law still holds in f(R,R^μνRμν)theory.For this complicated theory,we first determine the entropy of a black hole by using the Wald method,and then derive the energy of the black hole by using the new horizon first law,the degenerate Legendre transformation,and the gravitational field equations.For application,we consider the quadratic-curvature gravity,and first calculate the entropy and energy of a static spherically symmetric black hole,which are in agreement with the results obtained in the literature for a Schwarzschild-(A)dS black hole.