Molybdenum and tungsten oxide based gas sensors for high temperature detection of environmentally hazardous sulfur species

Abstract

a b s t r a c tThere is an increasing desire to control and monitor gas emissions from coal-fired power plants and other industrial systems. With this desire, there is a growing need for distributed gas sensors to monitor these emissions at high temperature ( > 600 • C), especially for pollutants such as SO 2 and H 2 S. The objective of this work was to investigate molybdenum and tungsten binary and ternary oxide thick films on a chemiresistive sensor platform for monitoring of gas sulfur species. The work evaluated the SO 2 sensitivity of WO 3 , MoO 3 , SrMoO 4 , NiMoO 4 , Sr 2 MgMoO 6-␦ (SMM), Sr 2 MgWO 6-␦ (SMW), NiWO 4 , and SrWO 4 compositions at 600-1000 • C. The SrMoO 4 composition at both the micro-and nano-particulate scale showed the most promise in sensitivity, stability and selectivity to SO 2 up to 1000 • C. Hydrothermallysynthesized nano-SrMoO 4 showed the highest sensor response with the R max values of −17.2, −50.2 and −40.5 upon exposure to a 20 min pulse of 2000 ppm of SO 2 at 600 • C, 800 • C and 1000 • C, respectively. Similar sensitivity trends were distinguished down to 1-5 min SO 2 pulses. The nano-SrMoO 4 showed low cross-selectivity to H 2 and CO. Finally, the nano-SrMoO 4 sensor was also tested with H 2 and coal syngas containing 5-100 ppm H 2 S, where high sensitivities were realized for both, but the sensing mechanism was altered in the latter (n-type to p-type semiconducting behavior). In order to better understand the sensing mechanism, extensive microstructural, electronic and chemical property characterizations were completed in this work.

Validation of a Terminally Amino Functionalized Tetra‐Alkyl Sn(IV) Precursor in Metal–Organic Chemical Vapor Deposition of SnO2 Thin Films: Study of Film Growth Characteristics, Optical, and Electrical Properties

“…The binding energy values of the detected groups match well with the literature known ones . More interestingly, the high concentration level of chemisorbed oxygen ions, 18.4 at.%, indicates potentially high sensitivity for chemical sensing and applicability of the deposited thin films as chemical sensors …”

Redox Stable Anode Materials for SOFC Application

“…As the dominant phase in the material systems under review is Monoclinic I2/a, the deviation from the 100% peak of Monoclinic I2/a (vertical dashed line in Figure 15) in the reviewed material system is shown in Table 1 as the function of lattice strain calculated using the Scherrer equation. Chemisorbed O 2ion was measured and showed a good match with the binding energies found in the literature [51][52][53][54][55][56][57][58]. Interstitial O 2ions were also detected at very close proximity in all the three compounds.…”

“…On transition metal oxides, it is widely accepted that there are two temperature maxima for the adsorption of oxygen, they are 25°C and just above 300°C. However this value is higher for the interstitially adsorbed O 2ions[51]. After deconvolution of the O 1s spectrum, three main chemical states of the oxygen were determined for CeNbO4, CeNb0.9Mo0.1O4 and CeNb0.8W0.2O4.Table 2show the details for the binding energy and FWHM values in addition to atomic concentration (at %) for all the elements investigated in this work.…”

Performance of activated carbons synthesized from fruit dehydration biowastes for supercapacitor applications

“…The large FWHM value, and the very low (0.1 eV) binding energy separation of the chemisorbed O 2− from hydroxyl groups within the AC-CSOS material, indicates that 9.2 at% for the chemisorbed oxygen is lower than indicated. The binding energy for chemisorbed O ions (O 2− ) was 1 eV higher than the values reported [41,42], FWHM values also followed same trend [43,44]. The higher values are axiomatically due to shift in the C main peak position as well as strong interaction with other oxygen surface groups.…”