Polybenzimidazole ͑PBI͒ film, a candidate polymer electrolyte membrane ͑PEM͒ for high-temperature ͑120-200°C͒ fuel cells, was cast from PBI/trifluoacetyl/H 3 PO 4 solution with constant molecular weight PBI powder and various acid doping levels. Conductivity measurements on these membranes were performed using an ac method under controlled temperature and relative humidity ͑RH͒. A complete set of conductivity data for H 3 PO 4 acid-doped PBI is presented as a function of temperature ͑60-200°C͒, RH ͑5-30%͒, and acid doping level ͑300-600 mol %͒. A mechanism of conductivity is proposed for the proton migration in this PBI/acid system based on this and previous work. Proton transfer in this system appears to occur along different paths for different doping levels, RHs, and temperatures. Hydrogen bonds immobilize the anions and form a network for proton transfer by a Grotthuss mechanism. The rate of proton transfer involving H 2 O is faster, leading to higher conductivity at higher RH. The order of the rate of proton transfer between various species is H 3 PO 4 (H 2 PO 4 Ϫ

Vanadium dioxide (VO), as a typical thermochromic material used in smart windows, is always limited by its weaker solar regulation efficiency (ΔT) and lower luminous transmittance (T). Except for common approaches such as doping, coating, and special structure, compositing is another effective method. The macroscopic thermochromic (from colorless to blue) ionic liquid-nickel-chlorine (IL-Ni-Cl) complexes are selected in this paper to be combined with VO nanoparticles forming a composite film. This novel scheme demonstrates outstanding optical properties: ΔT = 26.45% and T = 66.44%, T = 43.93%. Besides, the addition of the IL-Ni-Cl complexes endows the film with an obvious color change from light brown to dark green as temperature rises. This splendid visible thermochromic performance makes the composite film superior in function exhibiting and application of smart windows.

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In this Communication, we report MoO nanocomposites in which the near-infrared and visible light transmittance can be selectively modulated through the crystallinity. The MoO nanocomposites were fabricated by a hydrothermal method, and their optical properties were characterized by UV-Vis spectrometer. The obtained results proved the possibility to tune the nanocomposite's optical properties in the UV/Visible spectral region: crystalline MoO mainly regulates the near-infrared range (800-2600 nm), and amorphous MoO mainly changes the visible range from 350 nm to 800 nm and MoO , with semi-crystalline structures mainly modulating around 800-1000 nm. These kinds of optical modulations could be attributed to small polar absorption, free electron absorption and plasmon absorption according to different crystallinity. Our work may create new possibilities for future applications such as photochromism, photocatalysis, and electrochromism.