High temperature selective sensing of hydrogen with MgO-modified SrMoO4 micro-fibers

Abstract

Micro-fibers of Mg-doped SrMoO 4 (SrMoO 4 /MgO) were synthesized using a two-step hydrothermal technique. The SrMoO 4 /MgO micro-fibers were used as the sensing material within a solid-state, resistive-type sensor architecture. The material showed selective detection of hydrogen (H 2 ) up to 1000°C with high sensor response and stability for the given concentrations. The maximum relative resistance change values (Rmax) for SrMoO 4 /MgO for 4000 ppm H 2 in a N 2 atmosphere (1% O 2 ) were -31, -85, and -87.5 for 600, 800 and 1000°C, respectively. At 1000°C, and the same background atmosphere, the R max was only -2.5 and -12.5 to 4000 ppm CO and 2000 ppm SO 2 , respectively. Chemical characterization showed that the Mg was dissolved into the SrMoO 4 structure, in addition to residual MgO precipitate found within the final SrMoO 4 powder. The surface MgO was shown to affect the H 2 adsorption and dissociation processes in addition to high selectivity for H 2 in comparison to SO 2 and CO, while the dissolved Mg contributed to the alteration of the electronic properties, where the Schottky barrier height, band gap, and work function were all lowered. These combined effects resulted in the favorable sensitivity and high selectivity to H 2 , and also contributed to the increased stability at the elevated sensing temperatures.

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 …”

“…The large FWHMs of the Sn 3d 5/2 and O 1s peaks can be attributed to surface roughness and point defects on the surface . The defects become most likely manifest in oxygen vacancies and Sn 2+ ions.…”

Monitoring Surface Stoichiometry, Work Function and Valance Band of Tungsten Oxide (WO3), Molybdenum Oxide (MoO3) and Tin Oxide (SnO2) Thin Films as a Function of Temperature and Oxygen Partial Pressure with Advanced Surface Sensitive Techniques for Chemical Sensing Applications

“…The low deposition temperature and nonobligatory of heat treatment make it possible to obtain fine grains with high surface area. Despite the fact that few reports in recent years highlighted the importance of thickness/microstructure [1], the role of the defect sites, electronic and surface properties have not been well characterized with varying temperature and oxygen partial pressure [2], additionally understanding on chemisorbed oxygen species and oxygen vacancies ( °°) which facilitates the replenishment of chemisorbed oxygen ions on the surface [3] are also lacking. This report focus on a correlation of surface electronic, structural and chemical properties with the surface reactivity and sensing behavior of the ALD layers of tungsten oxide (WO3), molybdenum oxide (MoO3) and tin oxide (SnO2) in the thickness range of 20-100 nm by employing advanced synchrotron based surface sensitive spectral-microscopic techniques; near ambient x-ray photoelectron spectroscopy (NAP-XPS), x-ray induced photoelectron emission microscopy (XPEEM), x-ray photoelectron spectroscopy (XPS), ultraviolet photoelectron spectroscopy (UPS) and low energy electron microscopy (LEEM).…”

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.…”