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The dynamically switchable triple-band absorption enhancement over 96% of monolayer graphene in the visible to the near-infrared range is achieved by a simple configuration consisting of subwavelength grating and periodically distributed Bragg reflectors. The isolated optical field distribution enabled by the optical Tamm state (OTS), guided mode resonance (GMR) and Fabry–Perot (FP) mode allows each graphene layer to selectively absorb the incident light in different wavelengths at different parts of the structure, creating favorable conditions for the independent extraction of multi-channel signals. Moreover, the continuous regulation of the absorption wavelength is futher realized by varying the geometrical parameters and dielectric permittivity. Also, the electrical tunability of graphene allows the independent step modulation of the absorption efficiency of three eigenmodes, resulting in the real-time dynamic switching of the system's triple-band/dual-band/single-band operation modes. The proposed structure can be integrated as a dynamic component into other graphene-based multifunctional and switchable optoelectronic devices.

For lithium–sulfur batteries, 3D cathodes might be of interest for containing the active material and trapping the polysulfides during cycling, owing to their binder-free and freestanding features. In this work, the MoS2 grown on the 3D structured Carbon Cloth (CC@MoS2) is firstly used to fabricate the Li–S battery and the sulfur loading can be freely tuned by adjusting thermal annealing time at 200 °C. A two-step melt-diffusion strategy is reported for fabrication of cathodes, which involves in melting and diffusion of sulfur covered by CC@MoS2 composites instead of dissolution of sulfur in the toxic organic solvents. Compared with the non-polar carbon cloth, the CC@MoS2 composites exhibit better adsorption capacity for polysulfides due to more edge active sites, which could effectively facilitate polysulfide redox kinetics. The SEM images of the CC@MoS2 cathode after 300 cycles show that MoS2 can still maintain the nanosheet morphology. After 300 cycles at 0.5 C, the CC@MoS2 cathodes loaded with 2 mg sulfur exhibit a better reversible capacity of 698 mA h g−1 compared with CC@MoS2 loaded with 1 mg sulfur (604 mA h g−1) and CC@MoS2 loaded with 4 mg sulfur (420 mA h g−1). This work proposes an environmentally friendly method to fabricate the lithium–sulfur battery cathode material and the sulfur loading can be freely adjusted.

We report a simple one-step hydrothermal strategy for the fabrication of a C-MoS2/rGO composite with both large surface area and high porosity for the use as advanced electrode material in lithium–sulfur batteries. Double modified defect-rich MoS2 nanosheets are successfully prepared by introducing reduced graphene oxide (rGO) and amorphous carbon. The conductibility of the cathodes can be improved through the combination of amorphous carbon and rGO, which could also limit the dissolution of polysulfides. After annealing at different temperatures, it is found that the C-MoS2/rGO-6-S composite annealed at 600 °C yields a noticeably enhanced performance of lithium–sulfur batteries, with a high specific capacity of 572 mAh·g−1 at 0.2C after 550 cycles, and 551 mAh·g−1 even at 2C, much better than that of MoS2-S nanosheets (249 mAh·g−1 and 149 mAh·g−1) and C-MoS2/rGO-S composites (334 mAh·g−1 and 382 mAh·g−1). Our intended electrode design protocol and annealing process may pave the way for the construction of other high-performance metal disulfide electrodes for electrochemical energy storage.

Porous phosphide NixCoyP composite nanomaterials are successfully synthesized at different Ni/Co ratios (=0, 0.5, 1, and 2) to reduce 4-nitrophenol. The X-ray diffraction and X-ray photoelectron spectroscopy results demonstrate that the products are CoP, NiCoP/CoP, NiCoP, and NiCoP/Ni2P when the Ni/Co ratio is 0, 0.5, 1, and 2, respectively. The products exhibit different catalytic performance for reduction of 4-nitrophenol at room temperature. Among them, the pure NiCoP delivers a better catalytic efficiency with k app = 677.4 × 10 − 2 min − 1 and k = 338.7 ( Lg − 1 min − 1 ) , due to the synergy between Ni and Co atoms. The sequence of catalytic efficiency of different samples is CoP < NiCoP/CoP < NiCoP/Ni2P < NiCoP.

Creating adsorption sites by doping heteroatoms into the graphitic structures of carbon electrodes is an effective strategy for improving lithium storage in lithium-ion batteries. In this work, we prepared carbon nanotubes with controllable morphology and controllable nitrogen-doping level by a one-step pyrolysis method through adjusting the amount of urea used during synthesis. Under the synergistic effects of high temperature and Ni-catalyst migration, the carbon nanosheets generated by pyrolysis become coiled into tube-like structures. Characterization using Raman and x-ray photoelectron spectroscopy revealed that the B and N atoms were successfully co-doped into the resultant carbon nanotubes. When the obtained materials were used as lithium-ion battery anodes, reversible specific capacities of 337.11 and 187.62 mA h g−1 were achieved at current densities of 100 and 2000 mA g−1, respectively. Moreover, a capacity of 140.53 mA h g−1 was retained after 2000 cycles at a current density of 2000 mA g−1. The mechanism of lithium storage in these carbon materials was elucidated using cyclic voltammetry tests. Regarding other functional applications, the synthesized composite carbon nanotube material could also be used in other energy-storage battery systems, such as in the sulfur-carrying structures of lithium-sulfur batteries and in the three-dimensional porous structures of sodium batteries. ARTICLE HIGHLIGHTS: • We prepared carbon nanotubes with controllable morphology and nitrogen-doping levels through a one-step pyrolysis process by carefully adjusting the amount of urea used. • As lithium-ion battery anodes, the material exhibited reversible specific capacities of 337.11 and 187.62 mA h g−1 at current densities of 100 and 2000 mA g−1, respectively. • Capacity retention of 140.53 mA h g−1 was achieved after 2000 cycles at a current density of 2000 mA g−1. [ABSTRACT FROM AUTHOR]