Nanocrystalline Oxides NixCo3−xO4: Sub-ppm H2S Sensing and Humidity Effect

Abstract

In this work, p-type oxide semiconductors, Co3O4 and complex oxides NixCo3−xO4 (x = 0.04, 0.07, 0.1), were studied as materials for sub-ppm H2S sensing in the temperature range of 90–300 °C in dry and humid air. Nanocrystalline Co3O4 and NixCo3−xO4 (x = 0.04, 0.07, 0.1) were prepared by coprecipitation of cobalt and nickel oxalates from nitrate solutions and further annealing at 300 °C. The surface reactivity of the obtained materials toward H2S both in dry and humid atmosphere (relative humidity at 25 °C R.H. = 60%) was investigated using diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS). Sensor measurements showed a decrease in sensor signal toward 1 ppm H2S with an increase in Ni content because of a decrease in chemisorbed surface oxygen species. On the other hand, sensor signal increases for all samples with increasing the relative humidity that depends on reactivity of the surface hydroxyl groups, which stimulate the decomposition of surface sulfites and provide better surface regeneration at higher temperature. This assumption was additionally confirmed by the faster saturation of the conductivity curve and a decrease in the sensor response time in humid air.

Enhanced sensitivity of partial O-terminated H-diamond for H2S detection at room temperature

“…All adlayer molecules involving in the various chemical reactions are already adsorbed on the HD surface at the beginning and stay adsorbed throughout the process. The following two key reactions are considered in the dissolution reaction of H2S at the adsorbate layer [28,29]. When it is injected into the chamber with the presence of humidity, the following hydrolyzation reaction would take place [30].…”

Impact of Surface Faceting on Gas Sensing Selectivity of NiO: Revealing the Adsorption Sites of Organic Vapors on the {111} Facet

“…As a p -type semiconductor, nickel oxide (NiO) has been thoroughly explored as an active material in gas sensing due to its high catalytic activity in many organic compounds’ degradation. , For instance, NiO is an efficient catalyst for the methanol and ethanol oxidation processes, selective acetone hydrogenation, and oxidation of toluene. − Therefore, it is also well suited for the VOC sensing application, as the reduction and oxidation reactions are the fundamental working principles of gas detection in the sensor device. The NiO-based sensing materials have been proven to detect methanol, ethanol, formaldehyde, toluene, and many more. − NiO-based materials can be turned into various dimensionalities from 0D, 1D, 2D, and 3D hierarchical structures to significantly improve the gas sensing performance, as the morphology generally determines the specific surface area and the gas adsorption site. − More recently, researchers have also designed gas sensing materials with highly reactive facets to provide strong surface–adsorbate interactions. , For instance, the {111} surface facet is polar, Ni-terminated, and favorable for the adsorption and sensing of NO x gas, water molecules, and various VOCs. , However, the underlying mechanisms of molecular adsorption–desorption during the gas detection on the {111} surface facet of NiO, although hypothetically proposed in many experimental reports, were poorly investigated in detail by computational and theoretical simulations. This will surely accelerate the rational design of practical high-performance materials, not only for sensors but also for surface-related applications such as catalysis.…”

Nanocrystalline SnO2 Functionalized with Ag(I) Organometallic Complexes as Materials for Low Temperature H2S Detection

“…However, one of the main disadvantages is their low selectivity. Different approaches were used in order to increase the selectivity and sensitivity to hydrogen sulfide by various scientific groups: composites based on n-type and p-type semiconductors [7][8][9][10][11][12], decoration and modification with catalytic phases and nanoparticles [13][14][15][16], the morphology change [17][18][19][20][21]. The use of organic-inorganic hybrid materials as gas sensors is a promisingly developing area and of particular interest [22][23][24].…”