Unexpected Selective Absorption of Lithium in Thermally Reduced Graphene Oxide Membranes

Lithium plays an increasingly important role in scientific and industrial processes, and it is extremely important to extract lithium from a high Mg^(2+)/Li^(+) mass ratio brine or to recover lithium from the leachate of spent lithiumion batteries. Conventional wisdom shows that Li^(+) with low valence states has a much weaker adsorption(and absorption energy) with graphene than multivalent ions such as Mg^(2+). Here, we show the selective adsorption of Li^(+) in thermally reduced graphene oxide(rGO) membranes over other metal ions such as Mg^(2+), Co^(2+), Mn^(2+),Ni^(2+), or Fe^(2+). Interestingly, the adsorption strength of Li^(+) reaches up to 5 times the adsorption strength of Mg^(2+),and the mass ratio of a mixed Mg^(2+)/Li^(+) solution at a very high value of 500 : 1 can be effectively reduced to 0.7 : 1 within only six experimental treatment cycles, demonstrating the excellent applicability of the rGO membranes in the Mg^(2+)/Li^(+) separation. A theoretical analysis indicates that this unexpected selectivity is attributed to the competition between cation–π interaction and steric exclusion when hydrated cations enter the confined space of the rGO membranes.

Modulation of the cutoff wavelength in the spectra for solar selective absorbing coating based on high-entropy films

This paper demonstrates an intrinsic modulation of the cutoff wavelength in the spectra for solar selective absorbing coating based on high-entropy films.The(NiCuCrFeSi)N((NCCFS)N)films were deposited by a magnetron sputtering system.Rutherford backscattering spectroscopy analysis confirms the uniform composition and good homogeneity of these high-entropy films.The real and imaginary parts of the permittivity for the(NCCFS)N material are calculated on the basis of the reflectance spectral fitting results.A redshift cutoff wavelength of the reflectance spectrum with increasing nitrogen gas flow rate exists because of the different levels of dispersion when changing nitrogen content.To realize significant solar absorption,the film surface was reconstituted to match its impedance with air by designing a pyramid nanostructure metasurface.Compared with the absorptance of the as-deposited films,the designed metasurface obtains a significant improvement in solar absorption with the absorptance increasing from 0.74 to 0.99.The metasurfaces also show low mid-infrared emissions with thermal emittance that can be as low as 0.06.These results demonstrate a new idea in the design of solar selective absorbing surface with controllable absorptance and low infrared emission for high-efficiency photo-thermal conversion.

Tunable dual-band terahertz graphene absorber with guided mode resonances

A tunable dual-band terahertz absorber is designed and investigated. The unit cell of the proposed absorber consists of a graphene monolayer on a guided-mode resonant filter. The graphene absorber presents > 40% absorption at two resonance frequencies, which is attributed to the guided mode resonances with different mode numbers. The electric field intensity distribution is analyzed to disclose the physical mechanism of such a dual-band absorption effect. Furthermore,the influence of optical properties of graphene, including Fermi level and relaxation time, on the absorption spectra are investigated. Finally, the influence of geometric parameters on the absorption spectrum is studied, which will provide useful guidance for the fabrication of this absorber. We believe that the results may be useful for developing the next-generation graphene-based optoelectronic devices.

Promising thermal photonic management materials for sustainable human habitat

The spectral characteristics of outdoor structures,such as automobiles,buildings,and clothing,determine their energy interaction with the environment,from broad-spectrum absorption of light energy to high-efficiency thermal emission.Recently developed spectrally selective absorption(SSA)materials permit the reduction of energy loss from human habitat eco-system in the sustainable way and further reduce the utilization of fossil energy to achieve carbon neutrality.Here we review recent advances in SSA materials that enable rational and efficient management of thermal energy and provide new solutions for the resource base that supports human life like comfortable heat management,electricity production,and water supply.The basic principles of thermal photonic management,the regulation of SSA materials,and functional properties are summarized.An outlook discussing challenges and opportunities in SSA material energy management for comfortable living environments is finally presented,which expects the enormous potential of this interdisciplinary research in solving growing resource-shortage of human society.

Plasmonic light trapping for enhanced light absorption in film-coupled ultrathin metamaterial thermophotovoltaic cells

Ultrathin cells have gained increasing attention due to their potential for reduced weight, reduced cost and increased flexibility. However, the light absorption in ultrathin cells is usually very weak compared to the corresponding bulk cells. To achieve enhanced photon absorption in ultrathin thermophotovoltaic （TPV） cells, this work proposed a film-coupled metamaterial structure made of nanometer-thick gallium antimonide （GaSh） layer sandwiched by a top one-dimensional （1D） metallic grating and a bottom metal film. The spectral normal absorptance of the proposed structure was calculated using the rigorous coupled-wave algorithm （RCWA） and the absorption enhancement was elucidated to be attributed to the excitations of magnetic polariton （MP）, surface plasmon polariton （SPP）, and Fabry-Perot （FP） resonance. The mechanisms of MP, SPP, and FP were further confirmed by an inductor-capacitor circuit model, disper- sion relation, and phase shift, respectively. Effects of grating period, width, spacer thickness, as well as incidence angle were discussed. Moreover, short-circuit current density, open-circuit voltage, output electric power,and conversion efficiency were evaluated for the ultrathin GaSb TPV cell with a film-coupled metamaterial structure. This work will facilitate the development of next- generation low-cost ultrathin infrared TPV cells.

Novel advances in metal-based solar absorber for photothermal vapor generation

Access to safe drinking water has become an extremely urgent research topic wo rldwide.In recent years,the technology of solar vapor generation has been extensively explored as a potential and effective strategy of transforming elements content in seawater.In this review,the basic concepts and theories of metal-based photothermal vapor generation device(PVGD) with excellent optical and thermal regulatory are introduced.In the view of optical regulation,how to achieve high-efficiency localized evaporation in different evaporation system(i.e.,volumetric solar heating and interface solar heating) is discussed;from the aspect of thermal regulation,the importance of selective absorption surface for interfacial PVGD is analyzed.Based on the above discussion and analysis,we summarize the challenges of metal-based desalination device.