Gasochromic WO3 Nanostructures: History
View Latest Version
Please note this is an old version of this entry, which may differ significantly from the current revision.
Subjects: Nanoscience & Nanotechnology
Contributor:
Ali Mirzaei

Gasochromic WO3 nanostructure sensors work based on changes in their optical properties and color variation when exposed to hydrogen gas. They can work at low or room temperatures and, therefore, are good candidates for the detection of hydrogen leakage with low risk of explosion. Once their morphology and chemical composition are carefully designed, they can be used for the realization of sensitive, selective, low-cost, and flexible hydrogen sensors.

  • gasochromic
  • nanostructured WO3
  • gas sensor
  • hydrogen gas
  • sensing mechanism

1. Hydrogen Gas

Hydrogen is a gas with no color, odor, or taste and cannot be detected by human senses [1][2]. Due to its efficiency, renewability, and green nature, it can replace fossil fuels in the near future [3]. Nevertheless, because of its small size, high diffusion coefficient, and consequently easy permeation through most materials, it is difficult to store hydrogen. Furthermore, hydrogen is highly explosive with a broad flammability range (4–75 vol%) and possesses an extremely low ignition energy [4][5]. Therefore, it is important to develop low temperature, reliable and safe gas sensors for detecting hydrogen gas. So far, several gas sensors based on different mechanisms have been reported for sensing hydrogen, including fiber-optic [6], catalytic [7], electrochemical [8], acoustic [9], resistive [10], thermoelectric [11], and gasochromic  sensors [12]. Each of these sensors has its own merits and shortages [13]. For example, resistive gas sensors are inexpensive, simple in design and operation, highly responsive, and exhibit good stability [14][15][16]. However, they can only work efficiently at high temperatures [17], which increases the risk of hydrogen explosion during detection. Gasochromic sensors have the advantage of working at low temperatures, which can significantly decrease the risk of hydrogen explosion. Furthermore, in some cases, they can be fabricated on flexible substrates, with eye-readable color changes, which remarkably facilitate the detection of hydrogen in different places. In addition, the removal of electrical power from ambient atmosphere, high resistance to electromagnetic noise, and compatibility with optical fibers make them advantageous in hydrogen gas detection [18].

2. WO3 and Its Crystal Structures

Tungsten trioxide (WO3) is a very promising metal oxide with diverse properties. It has an n-type (Eg = 2.60–3.25 eV) [19][20] semiconducting nature and unique electrical properties. Further, it is transparent to visible and infrared light. Therefore, it has been used in different applications including smart windows [21], photocatalysts [22], solar cells [23], humidity sensors [24], and gas sensors [25]. Moreover, due to its excellent coloration efficiency [26], WO3 is the most used chromogenic material in photochromic, electrochromic, and gasochromic applications [27].
Tungsten oxide has a perovskite-type WO6 octahedral crystal structure. In its structure, W6+ ions occupy the corners of the octahedra, and oxygen ions are located at mid-crystal edge. In the ideal form, the octahedra are connected at the corners. The central atom (C) is absent and this defective perovskite configuration is often referred to as the ReO3 structure [28]. Similar to the behavior of most perovskites and ceramics, depending on the temperature, WO3 crystals can structurally transform in the following order: Monoclinic (ε-WO3, < −43 °C), triclinic (δ-WO3, −43 to 17 °C), monoclinic (γ-WO3, 17–330 °C), orthorhombic (β-WO3, 330–740 °C), and tetragonal (α-WO3 > 740 °C) [29][30]. The monoclinic crystal structure is the most stable at room temperature [30]. The large voids generated in WO6 octahedral networks in the WO3 structure induce some variations in the position of W and in the WO6 octahedron orientation. Thus, displacement of tungsten from the center of the octahedron and tilting of the WO6 octahedra are two kinds of distortions [26], which lead to 11 different structures of WO3 [31]. The gasochromic coloration of crystalline WO3 is associated with changes in its structure from monoclinic to tetragonal and cubic [32]. For example, Inouye et al. [33] reported crystal structure transition from monoclinic to tetragonal in RF-sputtered WO3 films upon exposure to hydrogen gas. However, the structure of hydrated WO3·xH2O sensors does not change during gasochromic detection of hydrogen gas [32].

3. Chromogenic: Definition, Materials and Basics

Chromogenics is a Greek word with the stem “chromo” for color. It refers to the study of materials whose optical properties (or color) change as a function of external ambient conditions [31]. Chromogenic materials generally have wide bandgaps and are transparent in the visible range, but they reversibly change from being transparent to a dark color in the presence of an electric field (electrochromic coloration), light (photochromic coloration), or when they are exposed to a gas (gasochromic coloration) [34]. Therefore, gasochromism refers to reversible changes in optical properties or color when a material is exposed to a gas [3][35]. Gasochromic materials exhibit a promising potential for use as gas sensors. WO3, which is light yellow in color, is one of the most important chromogenic materials known thus far. It exhibits a deep blue color upon exposure to hydrogen gas [36]. In addition to WO3, other materials reported for gasochromic applications include V2O5 [37][38][39][40], VOx [41], MOx [42], MoO3 [43], (MoO3)1−x (V2O5)x [44], mixed silver/nickel ammonium phosphomolybdate [45], (Ti-V-Ta)Ox [35], Ni(OH)2 [46], peroxopolytungstic acid [47][48], and metals like Y [49]. This effect has also been exploited for the detection of other gases such as volatile organic compounds [50], NO2 [51], H2S, SO2 [52], NH3 [53], XeF2 [54], cyclohexane [55], CO, and Cl2 [46]. Among the different gasochromic materials available, the most important ones are WO3 and MoOx. However, due to its weak color change properties and the existence of several phases whose formation depends on the growth method, molybdenum oxide has received less attention for gasochromic studies [56].

4. Gasochromic Properties of WO3 nanostructures

The ability of WO3 to undergo reversible changes in its optical properties when exposed to an electric field was first reported by Deb in 1973 [57]. Nineteen years later, Ito [58] reported the potential of WO3 for gasochromic studies. Thus far, the optical properties of WO3 nanostructures have been modulated by applying an electric field (electrochromism), UV irradiation (photochromism), or a gas (gasochromism) [59]. Gasochromic coloration of WO3 is mostly associated with hydrogen gas [35]. In contrast to the electrochromic response, the presence of catalytic noble metals on the surfaces of WO3 nanostructures is necessary to induce an acceptable gasochromic effect. The most common catalysts used are Pd [60][61], Au [30], and Pt [62][63]. They promote chemical reactions by reducing the activation energy between WO3 and hydrogen gas. Color changes occur in gasochromic WO3 sensors when H+ ions intercalate with the WO3 layer after the dissociation of gas molecules (H2) into atoms by the action of noble metals. The optical properties of WO3 films can be reversibly changed with the insertion and extraction of H+ ions and electrons into the WO3 films, which is accompanied by redox changes leading to the formation of W5+ ions [64][65]. Gasochromic measurements are often carried out by monitoring optical properties, such as absorbance/transmittance/reflectance in convenient wavelength ranges (visible-NIR) [66]. Such measurements offer simple, low-cost, and highly selective analytical methods for detecting specific gases [30]. In addition, the stability of the gas sensor can be enhanced as measurements are most often conducted at low or room temperatures.

This entry is adapted from the peer-reviewed paper 10.3390/app9091775

References

  1. Noh, H.-J.; Kim, H.-J.; Park, Y.M.; Park, J.-S.; Lee, H.-N. Complex behavior of hydrogen sensor using nanoporous palladium film prepared by evaporation. Appl. Surf. Sci. 2019, 480, 52–56.
  2. Kumar, A.; Kumar, A.; Chandra, R. Fabrication of porous silicon filled Pd/SiC nanocauliflower thin films for high performance H2 gas sensor. Sens. Actuators B Chem. 2018, 264, 10–19.
  3. Wu, C.-H.; Zhu, Z.; Huang, S.-Y.; Wu, R.-J. Preparation of palladium-doped mesoporous WO3 for hydrogen gas sensors. J. Alloys Compd. 2019, 776, 965–973.
  4. Boon-Brett, L.; Bousek, J.; Castello, P.; Salyk, O.; Harskamp, F.; Aldea, L.; Tinaut, F. Reliability of commercially available hydrogen sensors for detection of hydrogen at critical concentrations: Part I-Testing facility and methodologies. Int. J. Hydrogen Energy 2008, 33, 7648–7657.
  5. Sanger, A.; Kumar, A.; Kumar, A.; Chandra, R. Highly sensitive and selective hydrogen gas sensor using sputtered grown Pd decorated MnO2 nanowalls. Sens. Actuators B Chem. 2016, 234, 8–14.
  6. Xu, B.; Li, P.; Wang, D.; Zhao, C.-L.; Dai, J.; Yang, M. Hydrogen sensor based on polymer-filled hollow core fiber with Pt-loaded WO3/SiO2 coating. Sens. Actuator B Chem. 2017, 245, 516–523.
  7. Harley-Trochimczyk, A.; Chang, J.; Zhou, Q.; Dong, J.; Pham, T.; Worsley, M.A.; Maboudian, R.; Zettl, A.; Mickelson, W. Catalytic hydrogen sensing using microheated platinum nanoparticle-loaded graphene aerogel. Sens. Actuator B Chem. 2015, 206, 399–406.
  8. Li, Y.; Li, X.; Tang, Z.; Tang, Z.; Yu, J.; Wang, J. Hydrogen sensing of the mixed-potential-type MnWO4/YSZ/Pt sensor. Sens. Actuator B Chem. 2015, 206, 176–180.
  9. Sil, D.; Hines, J.; Udeoyo, U.; Borguet, E.J. Palladium nanoparticle-based surface acoustic wave hydrogen sensor. ACS Appl. Mater. Interfaces 2015, 7, 5709–5714.
  10. Mirzaei, A.; Sun, G.-J.; Lee, J.K.; Lee, C.; Choi, S.; Kim, H.W. Hydrogen sensing properties and mechanism of NiO-Nb2O5 composite nanoparticle-based electrical gas sensors. Ceram. Int. 2017, 43, 5247–5254.
  11. Kim, S.; Song, Y.; Lee, Y.-I.; Cho, Y.-H. Thermochemical hydrogen sensor based on Pt-coated nanofiber catalyst deposited on pyramidally textured thermoelectric film. Appl. Surf. Sci. 2017, 415, 119–125.
  12. Hübert, T.; Boon-Brett, L.; Black, G.; Banach, U. Hydrogen sensors-A review. Sens. Actuators B Chem. 2011, 157, 329–352.
  13. Ishihara, R.; Yamaguchi, Y.; Tanabe, K.; Makino, Y.; Nishio, K. Preparation of Pt/WO3-coated polydimethylsiloxane membrane for transparent/flexible hydrogen gas sensors. Mater. Chem. Phys. 2019, 226, 226–229.
  14. Kabcum, S.; Channei, D.; Tuantranont, A.; Wisitsoraat, A.; Liewhiran, C.; Phanichphant, S. Ultra-responsive hydrogen gas sensors based on PdO nanoparticle-decorated WO3 nanorods synthesized by precipitation and impregnation methods. Sens. Actuators B Chem. 2016, 226, 76–89.
  15. Mirzaei, A.; Leonardi, S.G.; Neri, G. Detection of hazardous volatile organic compounds (VOCs) by metal oxide nanostructures-based gas sensors: A review. Ceram. Int. 2016, 42, 15119–15141.
  16. Mirzaei, A.; Neri, G. Microwave-assisted synthesis of metal oxide nanostructures for gas sensing application: A review. Sens. Actuators B Chem. 2016, 237, 749–775.
  17. Mirzaei, A.; Hashemi, B.; Janghorban, K. α-Fe2O3 based nanomaterials as gas sensors. J. Mater. Sci. Mater. Electron. 2016, 27, 3109–3144.
  18. Maciak, E.; Pustelny, T. An optical ammonia (NH3) gas sensing by means of Pd/CuPc interferometric nanostructures based on white light interferometry. Sens. Actuators B Chem. 2013, 189, 230–239.
  19. Hu, J.; Wang, L.; Zhang, P.; Liang, C.; Shao, G. Construction of solid-state Z-scheme carbon-modified TiO2/WO3 nanofibers with enhanced photocatalytic hydrogen production. J. Power Source 2016, 328, 28–36.
  20. Li, Z.; Yang, M.; Dai, J.; Wang, G.; Huang, C.; Tang, J.; Hu, W.; Song, H.; Huang, P. Optical fiber hydrogen sensor based on evaporated Pt/WO3 film. Sens. Actuators B Chem. 2015, 206, 564–569.
  21. Huang, B.-R.; Lin, T.-C.; Liu, Y.-M. WO3/TiO2 core-shell nanostructure for high performance energy-saving smart windows. Solar Energy Mater. Solar Cells 2015, 133, 32–38.
  22. Tahir, M.B.; Sagir, M.; Shahzad, K. Removal of acetylsalicylate and methyl-theobromine from aqueous environment using nano-photocatalyst WO3-TiO2 @g-C3N4 composite. J. Hazard. Mater. 2019, 363, 205–213.
  23. Wang, Y.; He, B.; Wang, H.; Xu, J.; Ta, T.; Li, W.; Wang, Q.; Yang, S.; Tang, Y.; Zou, B. Transparent WO3/Ag/WO3 electrode for flexible organic solar cells. Mater. Lett. 2017, 188, 107–110.
  24. Faia, P.M.; Libardi, J. Response to humidity of TiO2:WO3 sensors doped with V2O5: Influence of fabrication route. Sens. Actuators B Chem. 2016, 236, 682–700.
  25. Sun, J.; Sun, L.; Han, N.; Pan, J.; Liu, W.; Bai, S.; Feng, Y.; Luo, R.; Li, D.; Chen, A. Ordered mesoporous WO3/ZnO nanocomposites with isotype heterojunctions for sensitive detection of NO2. Sens. Actuators B Chem. 2019, 285, 68–75.
  26. Hočevar, M.; Krašovec, U.O. Cubic WO3 stabilized by inclusion of Ti: Applicable in photochromic glazing. Solar Energy Mater. Solar Cells 2016, 154, 57–64.
  27. Ataalla, M.; Afify, A.S.; Hassan, M.; Abdallah, M.; Milanova, M.; Aboul-Enein, H.Y.; Mohamed, A. Tungsten-based glasses for photochromic, electrochromic, gas sensors, and related applications: A review. J. Non-Cryst. Solids 2018, 491, 43–54.
  28. Bange, K. Colouration of tungsten oxide films: A model for optically active coatings. Sol. Energy Mater. Sol. Cells 1999, 58, 1–131.
  29. Vogt, T.; Woodward, P.M.; Hunter, B.A. The high-temperature phases of WO3. J. Solid State Chem. 1999, 144, 209–215.
  30. Ahmad, M.Z.; Sadek, A.Z.; Yaacob, M.; Anderson, D.P.; Matthews, G.; Golovko, V.B.; Wlodarski, W. Optical characterisation of nanostructured Au/WO3 thin films for sensing hydrogen at low concentrations. Sens. Actuators B Chem. 2013, 179, 125–130.
  31. Pandurang, A. Transition Metal Oxide Thin Film Based Chromogenics and Devices, 1st ed.; Elsevier: Amsterdam, The Netherlands, 2017.
  32. Opara Krašovec, U.; Šurca Vuk, A.; Orel, B. IR Spectroscopic studies of charged-discharged crystalline WO3 films. Electrochim. Acta 2001, 46, 1921–1929.
  33. Inouye, A.; Yamamoto, S.; Nagata, S.; Yoshikawa, M.; Shikama, T. Hydrogen behavior in gasochromic tungsten oxide films investigated by elastic recoil detection analysis. Nucl. Instrum. Methods. Phys. Res. B 2008, 266, 301–307.
  34. Gogova, D.; Thomas, L.-K.; Camin, B. Comparative study of gasochromic and electrochromic effect in thermally evaporated tungsten oxide thin films. Thin Solid Films 2009, 517, 3326–3331.
  35. Domaradzki, J.; Kaczmarek, D.; Wojcieszak, D.; Mazur, M. Investigations of reversible optical transmission in gasochromic (Ti-V-Ta) Ox thin film for gas sensing applications. Sens. Actuators B Chem. 2014, 201, 420–425.
  36. Liu, B.; Cai, D.; Liu, Y.; Wang, D.; Wang, L.; Wang, Y.; Li, H.; Li, Q.; Wang, T. Improved room-temperature hydrogen sensing performance of directly formed Pd/WO3 nanocomposite. Sens. Actuators B Chem. 2014, 193, 28–34.
  37. Sanger, A.; Kumar, A.; Kumar, A.; Jaiswal, J.; Chandra, R. A fast response/recovery of hydrophobic Pd/V2O5 thin films for hydrogen gas sensing. Sens. Actuators B Chem. 2016, 236, 16–26.
  38. Rizzo, G.; Arena, A.; Bonavita, A.; Donato, N.; Neri, G.; Saitta, G. Gasochromic response of nanocrystalline vanadium pentoxide films deposited from ethanol dispersions. Thin Solid Films 2010, 518, 7124–7127.
  39. Ho, Y.; Chang, C.; Wei, D.; Dong, C.; Chen, C.; Chen, J.; Jang, W.; Hsu, C.; Chan, T.; Kumar, K. Characterization of gasochromic vanadium oxides films by X-ray absorption spectroscopy. Thin Solid Films 2013, 544, 461–465.
  40. Shanak, H.; Schmitt, H.; Nowoczin, J.; Ehses, K.-H. Effect of O2 partial pressure and thickness on the gasochromic properties of sputtered V2O5 films. J. Mater. Sci. 2005, 40, 3467–3474.
  41. Jang, W.-L.; Lu, Y.-M.; Lu, Y.-R.; Chen, C.-L.; Dong, C.-L.; Chou, W.-C.; Chen, J.-L.; Chan, T.-S.; Lee, J.-F.; Pao, C.-W. Effects of oxygen partial pressure on structural and gasochromic properties of sputtered VOx thin films. Thin Solid Films 2013, 544, 448–451.
  42. Hosseini, M.; Ranjbar, M. Plasmonic Au-MoO3 colloidal nanoparticles by reduction of HAuCl4 by blue MoOx nanosheets and observation of the gasochromic property. Plasmonics 2018, 13, 1897–1906.
  43. Kalanur, S.S.; Yoo, I.-H.; Seo, H. Pd on MoO3 nanoplates as small-polaron-resonant eye-readable gasochromic and electrical hydrogen sensor. Sens. Actuators B Chem. 2017, 247, 357–365.
  44. Chang, C.-C.; Luo, J.-Y.; Chen, T.-K.; Yeh, K.-W.; Huang, T.-W.; Hsu, C.-H.; Chao, W.-H.; Ke, C.-T.; Hsu, P.-C.; Wang, M.-J. Pulsed laser deposition of (MoO3)1-x (V2O5)x thin films: Preparation, characterization and gasochromic studies. Thin Solid Films 2010, 519, 1552–1557.
  45. Imani, M.; Tadjarodi, A. H2S gasochromic effect of mixed ammonium salts of phosphomolybdate nanoparticles synthesized by microwave assisted technique. Sens. Actuators B Chem. 2016, 237, 715–723.
  46. Fomanyuk, S.; Kolbasov, G.Y.; Chernii, V.Y.; Tretyakova, I. Gasochromic α, β–Ni (OH)2 films for the determination of CO and chlorine content. Sens. Actuators B Chem. 2017, 244, 717–726.
  47. Orel, B.; Grošelj, N.; Krašovec, U.O.; Gabršček, M.; Bukovec, P.; Reisfeld, R. Gasochromic effect of palladium doped peroxopolytungstic acid films prepared by the sol-gel route. Sens. Actuators B Chem. 1998, 50, 234–245.
  48. Orel, B.; Krašovec, U.O.; Grošelj, N.; Kosec, M.; Dražič, G.; Reisfeld, R. Gasochromic behavior of sol-gel derived Pd doped peroxopolytungstic acid (W-PTA) nano-composite films. J. Sol-Gel Sci. Technol. 1999, 14, 291–308.
  49. Ngene, P.; Radeva, T.; Slaman, M.; Westerwaal, R.J.; Schreuders, H.; Dam, B. Seeing hydrogen in colors: Low-cost and highly sensitive eye readable hydrogen detectors. Adv. Funct. Mater. 2014, 24, 2374–2382.
  50. Seo, C.; Cheong, H.; Lee, S.-H. Color change of V2O5 thin films upon exposure to organic vapors. Sol. Energy Mater. Sol. Cells 2008, 92, 190–193.
  51. Peter, C.; Schmitt, K.; Apitz, M.; Woellenstein, J. Metallo-porphyrin zinc as gas sensitive material for colorimetric gas sensors on planar optical waveguides. Microsyst. Technol. 2012, 18, 925–930.
  52. Xu, B.; Xu, L.; Gao, G.; Li, Z.; Liu, Y.; Guo, W.; Jia, L. Polyoxometalate-based gasochromic silica. New J. Chem 2008, 32, 1008–1013.
  53. Wang, Z.; Yuan, X.; Cong, S.; Chen, Z.; Li, Q.; Geng, F.; Zhao, Z. Color-changing microfiber-based multifunctional window screen for capture and visualized monitoring of NH3. ACS Appl. Mater. Interfaces 2018, 10, 15065–15072.
  54. Shim, G.; Lee, S.Y.; Kalanur, S.S.; Seo, H.J. Eye-readable gasochromic and electrical detectability of hydrogenated Pd-TiO2 to gaseous fluorine species. Appl. Surf. Sci. 2018, 462, 791–798.
  55. Hakoda, T.; Igarashi, H.; Isozumi, Y.; Yamamoto, S.; Aritani, H.; Yoshikawa, M. Gasochromic property of dehydrogenation-catalyst loaded tungsten trioxide. J. Phys. Chem. Solids 2013, 74, 200–204.
  56. Okumu, J.; Koerfer, F.; Salinga, C.; Pedersen, T.; Wuttig, M. Gasochromic switching of reactively sputtered molybdenumoxide films: A correlation between film properties and deposition pressure. Thin Solid Films 2006, 515, 1327–1333.
  57. Deb, S.K. Optical and photoelectric properties and colour centres in thin films of tungsten oxide. Philos. Mag. 1973, 27, 801–822.
  58. Ito, K.; Ohgami, T. Hydrogen detection based on coloration of anodic tungsten oxide film. Appl. Phys. Lett. 1992, 60, 938–940.
  59. Krašovec, U.O.; Orel, B.; Georg, A.; Wittwer, V. The gasochromic properties of sol-gel WO3 films with sputtered Pt catalyst. Sol. Energy 2000, 68, 541–551.
  60. Hemati, M.A.; Ranjbar, M.; Kameli, P.; Salamati, H. Gasochromic tungstenoxide films with PdCl2 solution as an aqueous hydrogen catalyst. Sol. Energy Mater. Sol. Cells 2013, 108, 105–112.
  61. Salinga, C.; Weis, H.; Wuttig, M. Gasochromic switching of tungsten oxide films: A correlation between film properties and coloration kinetics. Thin Solid Films 2002, 414, 288–295.
  62. Hsu, W.-C.; Peng, C.-H.; Chang, C.-C. Hydrogen sensing characteristics of an electrodeposited WO3 thin film gasochromic sensor activated by Pt catalyst. Thin Solid Films 2007, 516, 407–411.
  63. Zayat, M.; Reisfeld, R.; Minti, H.; Orel, B.; Svegl, F. Gasochromic effect in platinum-doped tungsten trioxide films prepared by the sol-gel method. J. Sol-Gel Sci. Technol. 1998, 11, 161–168.
  64. Orel, B.; Grošelj, N.; Krašovec, U.O.; Ješe, R.A.; Georg, A. IR spectroscopic investigations of gasochromic and electrochromic sol-gel-derived peroxotungstic acid/ormosil composite and crystalline WO3 films. J. Sol.-Gel. Sci. Technol. 2002, 24, 5–22.
  65. Garavand, N.T.; Mahdavi, S.; Ranjbar, M. The effect of operating temperature on gasochromic properties of amorphous and polycrystalline pulsed laser deposited WO3 films. Sens. Actuators B Chem. 2012, 169, 284–290.
  66. Ando, M. Recent advances in optochemical sensors for the detection of H2, O2, O3, CO, CO2 and H2O in air. TrAC Trends Anal. Chem. 2006, 25, 937–948.
More
© Text is available under the terms and conditions of the Creative Commons Attribution (CC BY) license; additional terms may apply. By using this site, you agree to the Terms and Conditions and Privacy Policy.
This entry is offline, you can click here to edit this entry!
Video Production Service
Feedback