Abstract
In this work we have fabricated hydrogen gas sensors based on undoped and 1 wt% multi-walled carbon nanotube (MWCNT)-doped tungsten oxide (WO3) thin films by means of the powder mixing and electron beam (E-beam) evaporation technique. Hydrogen sensing properties of the thin films have been investigated at different operating temperatures and gas concentrations ranging from 100 ppm to 50,000 ppm. The results indicate that the MWCNT-doped WO3 thin film exhibits high sensitivity and selectivity to hydrogen. Thus, MWCNT doping based on E-beam co-evaporation was shown to be an effective means of preparing hydrogen gas sensors with enhanced sensing and reduced operating temperatures. Creation of nanochannels and formation of p-n heterojunctions were proposed as the sensing mechanism underlying the enhanced hydrogen sensitivity of this hybridized gas sensor. To our best knowledge, this is the first report on a MWCNT-doped WO3 hydrogen sensor prepared by the E-beam method.
Highlights
Hydrogen (H2) is one of the most useful gases, being used in many chemical processes and various industries including aerospace, medical, petrochemical, transportation, and energy [1,2,3]
multi-walled carbon nanotube (MWCNT) were grown by the thermal chemical vapor deposition (CVD) process
MWCNT-doped WO3 thin film was fabricated by the E-beam evaporation technique onto Cr/Au interdigitated electrodes on an alumina substrate [29]
Summary
Hydrogen (H2) is one of the most useful gases, being used in many chemical processes and various industries including aerospace, medical, petrochemical, transportation, and energy [1,2,3]. H2 has attracted a great deal of attention as a potential clean energy source for the generation of automobiles and household appliances due to its perfectly clean combustion without any release of pollutants or greenhouse gases [4] This low molecular weighted gas can leak out and may cause fires or explosions when its concentration in air is between 4% and 75% by volume [5]. Addition of some noble metals such as Pt, Pd, or Au [22,23,24,25,26] to WO3 usually improves the sensitivity and selectivity to H2 gas These metal doped WO3 films can be prepared by several methods, including screen printing [22], sputtering [23,24] and sol-gel process [25,26]. MWCNTs were reported to be sensitive to H2, with good recovery times [27]
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