skip to main content


Title: Porous Tungsten Oxide: Recent Advances in Design, Synthesis, and Applications
Abstract

Tungsten oxide (WO3) has received ever more attention and has been highly researched over the last decade due to its being a low‐cost transition metal semiconductor with tunable, yet widely stable, band gaps. This minireview briefly highlights the challenges in the design and synthesis of porous WO3including methods, precursors, solvent effects, crystal phases, and surface activities of the porous WO3base material. These topics are explored while also drawing a connection of how the morphology and crystal phase affect the band gap. The shifts in band gap not only impact the optical properties of tungsten but also allow tuning to operate on different energy levels, which makes WO3highly desirable in many applications such as supercapacitors, batteries, solar cells, catalysts, sensors, smart windows, and bioapplications.

 
more » « less
PAR ID:
10233415
Author(s) / Creator(s):
 ;  ;  
Publisher / Repository:
Wiley Blackwell (John Wiley & Sons)
Date Published:
Journal Name:
Chemistry – A European Journal
Volume:
27
Issue:
36
ISSN:
0947-6539
Page Range / eLocation ID:
p. 9241-9252
Format(s):
Medium: X
Sponsoring Org:
National Science Foundation
More Like this
  1. Abstract

    Tungsten‐doped titanium‐dioxide (W‐TiO2) nanoparticles are successfully synthesized using a multiple‐diffusion‐flame burner with a separate center tube. Vaporized titanium tetra‐isopropoxide (TTIP) precursor issues from a center tube to produce TiO2nanoparticles, while a tungsten mesh, suspended above the surrounding multiple over‐ventilated hydrogen diffusion flames, serves as the solid‐phase metal doping source. At a lower tungsten loading rate, W‐TiO2nanoparticles are generated, as indicated by an obvious angle shift of 0.15° for the entire x‐ray diffraction spectrum. However, at a higher tungsten loading rate, homogenous nucleation of WOxoccurs before or concurrently with TiO2nucleation, producing mixed nanopowders, permitting fewer tungsten ions to be doped into TiO2. Ultraviolet–visible spectroscopic characterization reveals that the as‐synthesized W‐TiO2nanoparticles possess augmented absorbing ability in the visible‐light wavelength range, where the band gap is reduced from 3.20 to 3.05 eV, compared with that for the nondoped TiO2nanoparticles.

     
    more » « less
  2. Abstract

    A hierarchical nanocomposite of carbon microspheres decorated with tungsten oxide (WO3) nanocrystals resulted from the hydrothermal treatment of a precursor solution containing glucose and tungstic acid. The dehydration of glucose molecules formed oligosaccharides, which consequently carbonized, turning into carbon microspheres. The carbon microspheres then acted as a spherical nucleus onto which WO3nanocrystals grew via heterogeneous nucleation. The reaction product showed a phase junction of orthorhombic and monoclinic WO3,which transitioned to mix-phase of tetragonal and monoclinic WO3after a subsequent heat treatment at 600 °C in an inert condition. The electrochemical tests showed that incorporating WO3onto the carbon (WO3/C) resulted in a three-fold increase in the specific capacitance compared to WO3alone and a high coulombic and energy efficiencies of 98.2% and 92.8%, respectively. The nanocomposite exhibited supercapacitance with both Faradaic and non-Faradaic charge storage mechanisms. Electrochemical impedance spectroscopy showed a lower charge transfer resistance for the composite at Rct = 11.7Ω.

     
    more » « less
  3. Abstract

    Previous band structure calculations predicted Ag3AuSe2to be a semiconductor with a band gap of approximately 1 eV. Here, we report single crystal growth of Ag3AuSe2and its transport and optical properties. Single crystals of Ag3AuSe2were synthesized by slow‐cooling from the melt, and grain sizes were confirmed to be greater than 2 mm using electron backscatter diffraction. Optical and transport measurements reveal that Ag3AuSe2is a highly resistive semiconductor with a band gap and activation energy around 0.3 eV. Our first‐principles calculations show that the experimentally determined band gap lies between the predicted band gaps from GGA and hybrid functionals. We predict band inversion to be possible by applying tensile strain. The sensitivity of the gap to Ag/Au ordering, chemical substitution, and heat treatment merit further investigation.

     
    more » « less
  4. Abstract

    Recently, a new method to effectively engineer the bandgap of barium bismuth niobate (BBNO) double perovskite was reported. However, the planar electrodes based on BBNO thin films show low photocurrent densities for water oxidation owing to their poor electrical conductivity. Here, it is reported that the photoelectrochemical (PEC) activity of BBNO‐based electrodes can be dramatically enhanced by coating thin BBNO layers on tungsten oxide (WO3) nanosheets to solve the poor conductivity issue while maintaining strong light absorption. The PEC activity of BBNO/WO3nanosheet photoanodes can be further enhanced by applying Co0.8Mn0.2Oxnanoparticles as a co‐catalyst. A photocurrent density of 6.02 mA cm−2at 1.23 V (vs reversible hydrogen electrode (RHE)) is obtained using three optically stacked, but electrically parallel, BBNO/WO3nanosheet photoanodes. The BBNO/WO3nanosheet photoanodes also exhibit excellent stability in a high‐pH alkaline solution; the photoanodes demonstrate negligible photocurrent density decay while under continuous PEC operation for more than 7 h. This work suggests a viable approach to improve the PEC performance of BBNO absorber‐based devices.

     
    more » « less
  5. Abstract

    There are only a few examples of nanocrystal synthesis with thallium (Tl). Here, we report the synthesis of uniform, ligand‐stabilized colloidal nanocrystals of TlBr and Tl2AgBr3nanocrystals with average diameter ranging between 10 and 20 nm. TlBr nanocrystals are made by hot injection of trimethylsilyl bromide (TMSBr) into solutions of oleylamine, oleic acid and octadecene with thallium (III) or thallium (I) acetate. Tl2AgBr3nanocrystals form when silver (I) acetate is included in the reaction. The TlBr nanocrystals have CsCl crystal structure with a direct band gap of 3.1 eV. The Tl2AgBr3nanocrystals have trigonal dolomite crystal structure with an indirect band gap of 3.1 eV. The TlBr nanocrystals made with thallium (III) were sufficiently uniform to assemble into face‐centered cubic (fcc) superlattices.

     
    more » « less