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Few-layer Mg-deficient borophene nanosheets with a stoichiometric ratio Mg0.22B2 are prepared by oxidizing with I2 and delaminating from MgB2. The flakes have Mg atom deintercalation rate of 78% while maintaining the hexagonal structure of boron.

Developing new optimized bifunctional photocatalyst is of great significant for achieving the high-performance photo-assisted Li-O2 batteries. Herein, a novel bifunctional photo-assisted Li-O2 system is constructed by using siloxene nanosheets with ultra-large size and few-layers due to its superior light harvesting, semiconductor characteristic, and low recombination rate. An ultra-low charge potential of 1.90 V and ultra-high discharge of 3.51 V have been obtained due to the introduction of this bifunctional photocatalyst into Li-O2 batteries, and these results have realized the round-trip efficiency up to 185 %. In addition, this photo-assisted Li-O2 batteries exhibits a high rate (129 % round-trip efficiency at 1 mA cm-2 ), a prolonged cycling life with 92 % efficiency retention after 100 cycles, and the highly reversible capacity of 1170 mAh g-1 at 0.75 mA cm-2 . This work will open the vigorous opportunity for high-efficiency utilization of solar energy into electric system.

In order to increase the capacity and improve the sluggish Na+-reaction kinetics of anodes as sodium ion capacitors (SICs), a Ti2Nb2O9/CNF self-standing film electrode comprised of Ti2Nb2O9 nanosheets and carbon nanofibers has been fabricated via electrospinning HTiNbO5 nanosheets with PAN and subsequent carbonization treatment. The as-prepared Ti2Nb2O9/CNF film electrode possesses fast Na-ion intercalation kinetics and high conductivity during Na-ion storage, and it displays a high reversible capacity of 324 mA h g−1 at 0.1 A g−1. Additionally, it also delivers a superior rate capability of 204 mA h g−1 at a high current density of 4 A g−1, as well as an excellent cycling stability of 97% retention after 2000 cycles at 1 A g−1 in a half-cell test. A prototype Ti2Nb2O9/CNF//AC SIC full device was assembled by employing the presodiated Ti2Nb2O9/CNF anode and AC cathode, and it exhibits an high energy density of 129 W h kg−1 at a power density of 75 W kg−1 and a high power density (7560 W kg−1 with 63 W h kg−1), a good cycling performance of 85% capacitance retention after 10 000 cycles at 1 A g−1, suggesting that the Ti2Nb2O9/CNF electrode with excellent performance would be a very promising candidate as the anode for high-performance SICs.

For the disadvantages of both the slow reaction kinetics and the poor conductivity for Nb2O5 electrode materials as sodium-ion capacitors (SICs), Nb2O5 NRs/NMMCNF film electrode with good flexibility and high electrochemical property has been fabricated by electrospinning PAN/PMMA/H2Nb2O6·H2O homogeneous viscous suspension and followed by an annealing treatment, in which the precursor H2Nb2O6·H2O nanorods are obtained by grinding H2Nb2O6·H2O nanowires, and Nb2O5 nanorods are uniformly embedded in nitrogen doped microporous multichannel carbon nanofiber. Benefiting from the multichannel network structure, Nb2O5 NRs/NMMCNF film electrode delivers the fast kinetics of Na+-storage and the superior Na-ion storage performance, it delivers outstanding rate capability (101 mAh g−1 at 4 A g−1) and ultralong lifespan (91% capacity retention after 10,000 cycles at 2 A g−1). A Nb2O5 NRs/NMMCNF//AC SIC based on the Nb2O5 NRs@NMMCNF fiber film anode and the AC cathode is assembled. The energy density of the as-assembled device is as high as 91 Wh kg−1 and its maximum power density is 7499 W kg−1. This work offers a new structure design strategy toward intercalation-type metal oxide electrodes for application in SICs.

As a high-resolution sensor, it is very important to improve the spectral stability of microfiber Sagnac loop interferometer. A fiber Bragg grating (FBG) mode selecting method is proposed and demonstrated. The method can filter out some cladding modes by FBG in the Sagnac loop and make working modes energy more concentrated, which shows that the interference spectrum becomes more uniform. At the same time, the sensitivity and linearity of the sensor can be improved slightly by this method. In our experiment, the resolution of sensor can get 1.41 × 10-5 ∼ 7.49 × 10-6 in the liquid refractive index range of 1.3330∼1.38481. Moreover, this method can effectively improve the spectral stability of the interferometer, which shows that the dip wavelength absolute error of time fluctuation is improved from ±0.358 nm to 0.021 nm and from ±0.116 nm to 0.000 nm at 1536.6 nm and 1559.9 nm initial dip wavelength, respectively. This method also has advantages of compact structure, good mechanical properties, and easy preparation. On this basis, the FBG also can be replaced by various modes filters to develop more multifunctional high stability interferometers according to the detection needs.

A soft highly sensitive tactile sensor based on an in-fiber interferometer embedded in polydimethylsiloxane (PDMS) structure is studied. Theoretical simulation obtains that the high order sensing modes and PDMS can improve the sensitivity. Experiments show that different order sensing modes, derived by fast Fourier transform (FFT) and inverse FFT methods, present different sensing performance. Corresponding to high order mode, 1.3593 nm/kPa sensitivity and 37 Pa (0.015 N) detection limit is obtained. Meanwhile, it also shows very good stability, reproducibility, and response time. This study not only demonstrates a tactile sensor with high sensitivity but also provides a novel sensing modes analysis method.

Developing new optimized bifunctional photocatalyst is of great significant for achieving the high-performance photo-assisted Li-O

The preparation of two-dimensional boron (B) nanosheets, especially for borophene, is still a challenge because of its unique structure and complex B–B bonds in bulk boron. In the present work, a novel preparation technology for borophene with only a few layers and large flake sizes is developed by a solvothermal-assisted liquid phase exfoliation process, consisting of ball milling-thinning, solvothermal swelling, and probe ultrasonic delamination. The exfoliation effect of the bulk B precursors is related to the surface tension and Hildebrand parameter of the selected solvents such as acetone, N,N-dimethyl formamide (DMF), acetonitrile, ethanol, and N-methyl pyrrolidone (NMP), and a relative small surface tension when using solvents is favorable for the exfoliation of bulk B. Four-layer thick borophene and an average lateral size of 5.05 μm can be obtained in acetone as the exfoliating solvent. The surface composition of the exfoliated few-layer borophene with large flake size hardly changes, while the chemical state of B changes to some extent because they are partly oxidized on the surface by contaminates before and after exfoliation. This acetone solvothermal-assisted liquid phase exfoliation technique can be used to prepare high quality borophene with large horizontal sizes, and it will provide the basis to study few-layer borophene with large sizes further.

For the disadvantages of both the slow reaction kinetics and the poor conductivity for Nb

Ti2Nb2O9/reduced graphene oxide (Ti2Nb2O9/RGO) hybrid anode is fabricated by flocculation of HTiNbO5 nanosheets and graphene oxide (GO) nanosheets, followed by annealing HTiNbO5/GO composite at 500 °C in Ar for 1 h, in which HTiNbO5 nanosheets are prepared by ion-exchange and followed by exfoliating process using KTiNbO5 as precursor. HTiNbO5 nanosheets are topotactically transformed into Ti2Nb2O9 nanosheets and GO is reduced into RGO by calcining the HTiNbO5/GO composite, causing enhanced Na+-intercalation pseudocapacitive behavior and significantly improved conductivity for Ti2Nb2O9/RGO hybrid anode. Ti2Nb2O9/RGO hybrid anode delivers superior rate capability (206 mAh g−1 at 4 A g−1) and excellent cycling performance with 95% capacity retention at 1 A g−1 over 1000 cycles. A hybrid device is assembled using Ti2Nb2O9/RGO as the anode and activated carbon (AC) as the cathode, it shows a maximum high energy density of 96 Wh kg−1 at a power density of 75 W kg−1, and the energy density still maintains 39 Wh kg−1 when the power density achieves as high as 10029 W kg−1. Moreover, the assembled device displays good cycling stability with a capacity retention of 79% after 10,000 cycles. This work can provide new insights on fabrication of Ti-Nb oxides-graphene based composite anode for sodium ion capacitors.