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Ethanol is a volatile organic compound. Exposure to its vapors can cause breathing difficulties, headaches, drowsiness, and eye irritation. The development of highly sensitive ethanol sensors is of great significance in human health monitoring. In this work, 0.14 wt% rhodium on three-dimensionally ordered macroporous (3DOM) In2O3 (RhSA–In2O3) was synthesized by a UV light reduction method. The sensor based on RhSA–In2O3 exhibited high response (4590) to 50 ppm ethanol, high sensitivity (53.01 ppm−1) and an ultra-low detection limit (0.07 ppb). The ac-HAADF-STEM (aberration-corrected high angle annular dark-field scanning transmission electron microscopy), CO-DRIFTS (diffuse reflectance infrared Fourier transform spectroscopy), and XAFS (X-ray absorption fine structure) spectroscopy characterization results indicated that rhodium existed in the atomically dispersed state on In2O3, which provided abundant active sites and enhanced the ethanol-sensing response. The sensing mechanism was investigated using an ethanol-DRIFTS technique and an ethanol-acetaldehyde-CO2 reaction route with low activation energy (84.459 kJ mol−1) was proposed on RhSA–In2O3. [ABSTRACT FROM AUTHOR]

The development of uniform heterostructures for gas-sensing materials is promising to achieve both a fast response and recovery time at low gas levels and good selectivity at significantly high interference gas levels. Here we report the preparation of a ZIF-8-derived metal oxide semiconductor nanocomposite with a heterojunction structure and its application as acetone gas sensor. This heterojunction composite was fabricated through in situ growth of ZnFe2O4 nanoparticles (10–20 nm) on the outer surface of rhombic dodecahedral-shaped ZnO. Through the derivative strategy, the ZnFe2O4/ZnO heterojunction sensor had a high response value of 225 ± 15 and a fast response time of 6 s to 100 ppm of acetone at the optimum working temperature of 260 °C. Furthermore, the response value reached 5.1 for only 1.8 ppm of acetone even under extremely high humidity (85%). To obtain a demonstration of the concept, an in-depth investigation of the sensing performances and the microstructure and surface state of ZnO and ZnFe2O4/ZnO heterojunction materials was carried out. We found that the excellent acetone sensitivity enhancement could largely be attributed to the ultrahigh number of free electrons and the abundant active sites generated by the tightly bound n–n heterojunction structure of ZnFe2O4/ZnO and the morphological characteristics. The large specific surface area of every sensing domain was the secondary factor in enhancing the gas-sensing properties. It suggests that this design for fabricating uniform and sensitive gas sensors may facilitate potential applications in detecting acetone gas. [ABSTRACT FROM AUTHOR]

Metal oxide semiconductor (MOS) gas sensor is an effective tool for NO2 detection. However, their performance is seriously influenced by humidity due to water vapor poisoning, and it remains a challenge to develop an anti-humidity NO2 MOS sensor. In this work, a humidity-independent, highly sensitive and selective NO2 sensor based on In2O3 nanoflowers decorated with graphite nanoflakes was fabricated, which exhibited excellent anti-humidity and stability (response fluctuation within 7%) in a wide relative humidity (RH) range of 20% - 90%. The fabricated sensor had a high response of 10 to ppb level NO2 (RH 80%). Besides, the sensor exhibited good selectivity, low operating temperature (75 °C) and rapid response speed (50 s to 5 ppm NO2). The reason for the excellent anti-humidity function was investigated. Large amounts of polar groups were formed on the graphite nanoflakes after hydrothermal treatment, which enhanced the interaction between the graphite and In2O3 and made the surface of the composites have a strong water absorption function. Moreover, the intrinsic hydrophobic property of the graphite can effectively block the interference of water vapor to the moisture-sensitive In2O3. Our work provides a new idea for enhancing the anti-humidity performance of the MOS sensors and can broaden their applications in a variety of complex environments. [ABSTRACT FROM AUTHOR]

Direct conversion of methane into value‐added chemicals, such as methanol under mild conditions, is a promising route for industrial applications. In this work, atomically dispersed Rh on TiO2 suspended in an aqueous solution was used for the oxidation of methane to methanol. Promoted by copper cations (as co‐catalyst) in solution, the catalysts exhibited high activity and selectivity for the production of methanol using molecular oxygen with the presence of carbon monoxide at 150 °C with a reaction pressure of 31 bar. Millimole level yields of methanol were reached with the selectivity higher than 99 % using the Rh/TiO2 catalysts with the promotion of the copper cation. CO was the reductive agent to generate H2 from H2O, which led to the formation of H2O2 through the reaction of H2 and O2. Atomically dispersed Rh activated the C−H bond in CH4 and catalyzed the oxidation using H2O2. Copper cations maintained the low‐valence state of Rh. Moreover, copper acted as a scavenger for suppressing the overoxidation, thus leading to the high selectivity of methanol. [ABSTRACT FROM AUTHOR]

Direct conversion of methane into value‐added chemicals, such as methanol under mild conditions, is a promising route for industrial applications. In this work, atomically dispersed Rh on TiO2 suspended in an aqueous solution was used for the oxidation of methane to methanol. Promoted by copper cations (as co‐catalyst) in solution, the catalysts exhibited high activity and selectivity for the production of methanol using molecular oxygen with the presence of carbon monoxide at 150 °C with a reaction pressure of 31 bar. Millimole level yields of methanol were reached with the selectivity higher than 99 % using the Rh/TiO2 catalysts with the promotion of the copper cation. CO was the reductive agent to generate H2 from H2O, which led to the formation of H2O2 through the reaction of H2 and O2. Atomically dispersed Rh activated the C−H bond in CH4 and catalyzed the oxidation using H2O2. Copper cations maintained the low‐valence state of Rh. Moreover, copper acted as a scavenger for suppressing the overoxidation, thus leading to the high selectivity of methanol. [ABSTRACT FROM AUTHOR]

Direct conversion of methane into value‐added chemicals, such as methanol under mild conditions, is a promising route for industrial applications. In this work, atomically dispersed Rh on TiO2 suspended in an aqueous solution was used for the oxidation of methane to methanol. Promoted by copper cations (as co‐catalyst) in solution, the catalysts exhibited high activity and selectivity for the production of methanol using molecular oxygen with the presence of carbon monoxide at 150 °C with a reaction pressure of 31 bar. Millimole level yields of methanol were reached with the selectivity higher than 99 % using the Rh/TiO2 catalysts with the promotion of the copper cation. CO was the reductive agent to generate H2 from H2O, which led to the formation of H2O2 through the reaction of H2 and O2. Atomically dispersed Rh activated the C−H bond in CH4 and catalyzed the oxidation using H2O2. Copper cations maintained the low‐valence state of Rh. Moreover, copper acted as a scavenger for suppressing the overoxidation, thus leading to the high selectivity of methanol. [ABSTRACT FROM AUTHOR]

Direct conversion of methane into value‐added chemicals, such as methanol under mild conditions, is a promising route for industrial applications. In this work, atomically dispersed Rh on TiO2 suspended in an aqueous solution was used for the oxidation of methane to methanol. Promoted by copper cations (as co‐catalyst) in solution, the catalysts exhibited high activity and selectivity for the production of methanol using molecular oxygen with the presence of carbon monoxide at 150 °C with a reaction pressure of 31 bar. Millimole level yields of methanol were reached with the selectivity higher than 99 % using the Rh/TiO2 catalysts with the promotion of the copper cation. CO was the reductive agent to generate H2 from H2O, which led to the formation of H2O2 through the reaction of H2 and O2. Atomically dispersed Rh activated the C−H bond in CH4 and catalyzed the oxidation using H2O2. Copper cations maintained the low‐valence state of Rh. Moreover, copper acted as a scavenger for suppressing the overoxidation, thus leading to the high selectivity of methanol. [ABSTRACT FROM AUTHOR]