Highly sensitive and selective detection
of trace nitrogen dioxide
(NO2) in a complex outdoor air environment is an urgent
need to guarantee human health and a beautiful environment. The effective
combination of heterostructure and light irradiation is an important
strategy to achieve high-performances gas sensors. However, the effect
of light irradiation on gas-sensitive properties of heterostructure
materials is not yet clear, and it is urgent to clarify the relationship
between light irradiation and heterostructure for gas-sensing materials.
Herein, a 530 nm-light-assisted Au–MoS2 gas sensor
with a low detection limit as well as robust antihumidity interference
ability is developed through introducing the localized surface plasmon
resonance (LSPR) effect of Au nanoparticles (NPs). Under 530 nm light
illumination, a Au–MoS2 gas sensor can achieve limit
detection of NO2 as low as 10 ppb without operating temperature
along with robust antihumidity ability. The optical simulation and
experimental results show that the modification of MoS2 by Au NPs (diameter: 30 nm) combined with the matching light-assisted
(530 nm) gas detection mode can make MoS2 fully absorb
visible light and effectively improve the extinction cross section
by taking full advantage of the LSPR effect, which is the primary
reason for the enhanced performances of a MoS2-based gas
sensor. This work provides theoretical and experimental guidance for
gas sensors to effectively enhance the ability of gas detection by
means of the light-assisted mode at room temperature, which opens
up a unique approach to design high-performance gas sensors for trace-level
gas detection.
Two CeO 2 catalysts were fabricated by dry ball milling in the absence or presence of organic ligand, denoted as CeO 2 -A and CeO 2 -B, respectively, and tested for selective catalytic reduction of NO by NH 3 (NH 3 -SCR). It was found that the CeO 2 -B catalyst exhibited high NH 3 -SCR activities as well as high SO 2 and H 2 O resistance. The characterizations of nitrogen adsorption (BET), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TG), Raman spectroscopy, temperature-programmed reduction (H 2 -TPR), temperature-programmed desorption (SO 2 -TPD) and X-ray photoelectron spectroscopy (XPS) revealed that the addition of adipic acid in the synthetic procedure leaded to a high reducibility of cerium species and a special surface microstructure, including relative high surface defects and hierarchical pore structure of the CeO 2 catalyst, which played important roles in enhancing NH 3 -SCR performance. Meanwhile, the interaction between SO 2 and CeO 2 under different condition was investigated in detail by in situ diffuse reflection infrared Fourier transform spectroscopy (DRIFTS) and SO 2 -TPD. The data suggested that the high resistance to SO 2 poisoning of CeO 2 -B could be explained by a low amount of sulfur species formation and a low speed transformation of sulfites to sulfates on the ceria catalyst due to its special surface microstructure.
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