Three-dimensional (3D) ordered mesoporous Ag/Co3O4 and K–Ag/Co3O4 catalysts were successfully prepared on the basis of 3D-Co3O4. All catalysts possess 3D mesoporous structures, which are not affected ...due to Ag and K addition. Ag nanoparticles, uniformly dispersed and supported on the polycrystalline wall of K–Ag/Co3O4, provide sufficient active sites for HCHO oxidation reaction. 1.7% K–Ag/Co3O4 has turnover frequencies (TOFs) of 0.22 s–1 at 60 °C and 2.62 s–1 at 100 °C, and its HCHO conversion at room temperature is 55% (HCHO 100 ppm and GHSV 30000 h–1). The addition of K+ ions obviously promotes the catalytic performance for HCHO oxidation due to surface OH– species provided by K+ ions and more abundant Ag(111) active faces, Co3+ cations and surface lattice oxygen (O2–) species generated by stronger interaction between Ag and Co and anion lattice defects. Ag(111) faces, Co3+ ions, and O2– are active species. Combined with TOFs, at low temperature (<80 °C), the HCHO catalytic activity on K–Ag/Co3O4 catalyst largely depends on the surface OH– species at the perimeter of the Ag(111) facets; at relatively high temperature (>80 °C), the surface OH– species are consumed and replaced quickly, and their supplement relies on the migration of O2– species from 3D-Co3O4 support. The pathway of reaction for HCHO oxidation on the K–Ag/Co3O4 follows the HCHO → CHOO– + OH– → CO2 + H2O route.
Besides the help of diverse signals as mentioned above, another part contributing to the understanding of the brain is machine learning methods. According to their study, the deep learning-based ...method can help refine the frequency band associated with the exercise. A much narrower frequency band (27–29 Hz) was identified, compared to a usually used frequency band of 15–30 Hz. ...the exercise-related brain areas were also identified, which were the contralateral and ipsilateral sensorimotor areas, contralateral prefrontal area, and occipital area.
The high-efficiency catalyst is the key factor of volatile organic compounds (VOCs) catalytic combustion. Herein, hierarchical core–shell Al2O3@Pd-CoAlO (Pd-CoAlO-Al) microspheres have been ...successfully prepared and used for toluene combustion. The experimental results reveal that the core–shell Pd-CoAlO-Al exhibits outstanding catalytic efficiency due to the homogeneous distribution of Pd-CoAlO nanosheets on Al2O3 supports and the strong interaction between the catalytically active Pd-CoAlO nanosheets and the Al2O3 supports. In particular, the catalytically active PdO contributes to the excellent catalytic efficiency. In addition, the in situ DRIFTS results indicate that the benzoate species are the main intermediate species in toluene combustion.
MO x /ABO3 is a promising catalyst for the high-efficiency removal of volatile organic compounds. However, this catalyst is limited on practical applications due to its complex synthesis procedure ...and high cost. In this work, the MnO2/LaMnO3 catalyst was prepared in situ using a facile one-step method for the first time, in which partial La cations were selectively removed from three dimensionally chain-like ordered macroporous (3DOM) LaMnO3 material. After selective removal, the obtained MnO2/LaMnO3 sample expressed an excellent catalytic performance on toluene oxidation. Toluene could be completely oxidized into CO2 and H2O at 290 °C over the MnO2/LaMnO3 catalyst with a toluene/oxygen molar ratio of 1/100 and a space velocity of 120 000 mL/(g h). In addition, the apparent activation energy value of MnO2/LaMnO3 was 57 kJ/mol, which was lower than those of other metal oxides catalysts. According to O2-TPD and XPS results, it is concluded that the high catalytic performance of MnO2/LaMnO3 was mainly associated with the large amount of oxygen species and the excellent lattice oxygen mobility. MnO2/LaMnO3 is a promising catalyst for the practical removal of volatile organic compounds due to its high efficiency, good stability, low cost, and convenient preparation.
Photocatalytic synthesis of ammonia (NH3) holds significant potential compared with the Haber–Bosch process. However, the reported photocatalysts suffer from low efficiency owing to localized ...electron deficiency. Herein, Ru‐SA (single atoms)/HxMoO3−y hybrids with abundant of Mon+ (4<n<6) species neighboring oxygen vacancies (OV) are synthesized via a H‐spillover process. Detailed characterizations demonstrate that Ru‐SA/HxMoO3−y hybrids can quantitatively produce NH3 from N2 and H2 through the presence of dual active centers (Ru SA and Mon+). The Ru SA boost the activation and migration of H2, and Mon+ species act as the trapping sites of localized electrons and the adsorption and dissociation sites of N2, finally leading to NH3 synthesis on Mon+−OH. The NH3 generation rate is up to 4.0 mmol h−1 g−1, accompanied by an apparent quantum efficiency over 6.0 % at 650 nm.
Ru‐SA (single atom)/HxMoO3−y hybrids with abundant Mon+ species neighboring oxygen vacancies are synthesized via a H‐spillover process. More importantly, Ru‐SA/HxMoO3−y hybrids can quantitatively produce NH3 from N2 and H2 by the effect of dual active centers (Ru SA and Mon+).
Catalytic combustion technology is one of the effective methods to remove VOCs such as toluene from industrial emissions. The decomposition of an aromatic ring via catalyst oxygen vacancies is ...usually the rate-determining step of toluene oxidation into CO2. Series of CeO2 probe models were synthesized with different ratios of surface-to-bulk oxygen vacancies. Besides the devotion of the surface vacancies, a part of the bulk vacancies promotes the redox property of CeO2 in toluene catalytic combustion: surface vacancies tend to adsorb and activate gaseous O2 to form adsorbed oxygen species, whereas bulk vacancies improve the mobility and activity of lattice oxygen species via their transmission effect. Adsorbed oxygen mainly participates in the chemical adsorption and partial oxidation of toluene (mostly to phenolate). With the elevated temperatures, lattice oxygen of the catalysts facilitates the decomposition of aromatic rings and further improves the oxidation of toluene to CO2.
The water cloud model (WCM) is a widely used radar backscatter model applied to SAR images to retrieve soil moisture over vegetated areas. The WCM needs vegetation descriptors to account for the ...impact of vegetation on SAR backscatter. The commonly used vegetation descriptors in WCM, such as Leaf Area Index (LAI) and Normalized Difference Vegetation Index (NDVI), are sometimes difficult to obtain due to the constraints in data availability in in-situ measurements or weather dependency in optical remote sensing. To improve soil moisture retrieval, this study investigates the feasibility of using all-weather SAR derived vegetation descriptors in WCM. The in-situ data observed at an agricultural crop region south of Winnipeg in Canada, RapidEye optical images and dual-polarized Radarsat-2 SAR images acquired in growing season were used for WCM model calibration and test. Vegetation descriptors studied include HV polarization backscattering coefficient ( σ H V ° ) and Radar Vegetation Index (RVI) derived from SAR imagery, and NDVI derived from optical imagery. The results show that σ H V ° achieved similar results as NDVI but slightly better than RVI, with a root mean square error of 0.069 m3/m3 and a correlation coefficient of 0.59 between the retrieved and observed soil moisture. The use of σ H V ° can overcome the constraints of the commonly used vegetation descriptors and reduce additional data requirements (e.g., NDVI from optical sensors) in WCM, thus improving soil moisture retrieval and making WCM feasible for operational use.
One-pot synthesized Cu–SSZ-13 catalyst treated with dilute HNO3 achieved superior activity and selectivity in the selective catalytic oxidation (SCO) of NH3 to nitrogen, in comparison with other ...zeolite-based catalysts and most of metal-oxide catalysts. Furthermore, the catalyst showed the similar or even higher catalytic activity than the partial noble-metal catalysts, and meanwhile its N2 selectivity was superior to most noble-metal catalysts. The characterization results demonstrated that more Cu2+ ions existing in Cu–SSZ-13 catalyst were advantageous to its NH3–SCO activity. The in situ DRIFTS results indicated that the reactivity of NH3 species adsorbed on Lewis and Brønsted acid sites over Cu–SSZ-13–O–H catalyst depended on the reaction temperature. The results of this study suggest the one-pot synthesized Cu–SSZ-13 is a promising NH3–SCO catalyst for practical application, either mobile or stationary pollution sources.
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