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Beta-manganese dioxide (β-MnO) microrods were hydrothermally synthesized from ammonium persulfate [(NH)SO] solution using manganese sulfate (MnSO) as reductant at 180 °C for 3 h. The characterizations, including X-ray diffraction, scanning electron microscopy, and transmission electron microscopy, showed that the crystallinity and morphology of the as-synthesized samples were well-defined β-MnO microrods with the diameters of about 100 nm and lengths of about 2-4 μm. To explore the optimal degradation conditions, the as-synthesized β-MnO microrods were employed into the degradation of methyl orange dye solution with the concentration of 20 mg/L in the presence of H with pH values equalling 1.0, 1.5, 2.0, 3.0, 5.0, and 7.0, respectively. The results indicate that the degradation efficiency could reach 98% after 9 min at the pH value of 1.0 or 2.0. Also, the lower the pH value, the higher the degradation efficiency. Based on these experimental results, a proper mechanism of the degradation process of methyl orange is proposed and the rationality of the mechanism is further investigated through the scientific control tests. [ABSTRACT FROM AUTHOR]

Macro-/nanoporous Al-doping ZnO powders with enhanced gas sensing properties are prepared by a solution combustion method using Zn(CH 3 COO) 2 ·2H 2 O, Zn(NO 3 ) 2 ·6H 2 O, Al(NO 3 ) 3 ·9H 2 O, N 2 H 4 ·H 2 O and C 2 H 5 NO 2 as precursors. Characterization by TEM, SEM and BET techniques demonstrates that the Al-doping ZnO powders have a coral-like morphology with a hierarchically porous structure from macro pores, with the wall containing smaller mesopores. The gas-sensing characteristics of the ZnO samples with different Al-doping concentrations are investigated and the results indicate that the gas sensor prepared from 2.5 at% Al doping ZnO powders shows the highest gas sensitivity and selectivity towards n -butanol. A maximum gas response of 751.95 towards 100 ppm n -butanol is achieved at the operating temperature of 300 °C. The mechanisms of responses are also proposed considering the unique material structure. [ABSTRACT FROM AUTHOR]

Pure and Al-doped macro-/nanoporous ZnO were synthesized via solution combustion method by using zincacetate dihydrate (Zn(CH 3 COO) 2 ·2H 2 O), zinc nitrate hexahydrate (Zn(NO 3 ) 2 6H 2 O), aluminum nitrate nonahydrate (Al(NO 3 ) 3 ·9H 2 O), hydrazine hydrate (N 2 H 4 ·H 2 O) and glycine (C 2 H 5 NO 2 ) as precursors. The morphology, structure and catalytic properties of the as-synthesized macro-/nanoporous products were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), UV–Vis spectroscopy, Brunauer-Emmett-Teller (BET) nitrogen adsorption-desorption and Fourier transform infrared spectroscopy (FTIR), respectively. Pure and Al-doped ZnO have coral-like shape with the pores size ranging from several nanometers to ten micrometers. The walls of the macropores contain smaller nanopores, exhibiting the hierarchically porous morphology. The catalytic activities of the as-synthesized samples were tested by measuring the degradation efficiency of azo dye Congo red (CR) under visible light, UV light and dark light, respectively. The results show excellent removal capacity for organic pollutants CR in wastewater. Macro-/nanoporous Al-ZnO with different contents of Al have better catalytic degradation efficiency than pure ZnO. The experimental results indicate the potential use of macro-/nanoporous Al-ZnO for catalytic degradation of Congo red dye in different environments, which provides a potentially low-cost alternative for the remediation of azo-dye effluents. [ABSTRACT FROM AUTHOR]

Three-dimensional macro/mesoporous CoO-CeO was prepared via a facile self-sustained decomposition of metal-organic complexes. Porous CoO-CeO was characterized using X-ray diffraction, scanning electron microscopy/transmission electron microscopy imaging, N adsorption/desorption and X-ray photoelectron spectroscopy to examine the morphology and microstructure to find out the cause. CoO-CeO with the 3D hierarchical porous structure consisting of nanoparticles is a coral-like shape with a size of tens of micrometers and exhibits the hierarchically porous morphology, in which the walls of the macropores contain smaller mesopores. The catalytic performance of the porous CoO-CeO for CO oxidation has been studied. Among the obtained catalysts, the porous CoO-CeO with 20 wt% Co exhibits the best catalytic activity and the 50 % CO conversion can be reached at 74 °C. The presence of transition metal element Co can promote the production of oxygen vacancies and improve oxygen mobility, which result in enhancing the oxygen-storage capacity of porous CoO-CeO and its catalytic performance for CO conversion. Graphical Abstract: [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

Three-dimensional macro/mesoporous tricobalt tetraoxide Co 3 O 4 was prepared via a facile self-sustained decomposition using the complexes of metallic salts and organics (metal–organic complexes). Porous Co 3 O 4 material was characterized using X-ray powder diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Raman spectroscopy, and X-ray photoelectron spectrum (XPS) to examine the morphology and microstructure to find out the cause. Co 3 O 4 with the 3D hierarchical porous structure consisting of nanoparticles has a coral-like shape with a size of tens of micrometers and exhibits the hierarchically porous morphology, in which the walls of the macropores contain smaller mesopores. The catalytic performance of the porous Co 3 O 4 for CO oxidation has been studied with a continuous flow fixed-bed quartz microreactor. The porous Co 3 O 4 exhibits excellent catalytic activity for CO oxidation, the CO conversion rate reaches 100% at 140 °C. [ABSTRACT FROM AUTHOR]

Meso- and macroporous coral-like Co 3 O 4 was synthesized via a facile self-sustained decomposition using the complexes of metallic salts and organics (metal-organic complexes). Porous Co 3 O 4 material was characterized using X-ray powder diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Raman spectroscopy, and X-ray photoelectron spectrum (XPS) to examine the morphology and microstructure to find out the cause. Co 3 O 4 with the meso- and macroporous structure consisting of nanoparticles has a coral-like shape with a size of tens of micrometers and exhibits the hierarchically porous morphology, in which the walls of the macropores contain smaller mesopores. The gas-sensing characteristics of the porous Co 3 O 4 for volatile organic compounds (VOCs) were investigated. The gas response to 1000 ppm n-butanol reaches a maximum of 27.7 at an operating temperature of 120 °C, and about five times of the Co 3 O 4 particles. The porous Co 3 O 4 also exhibits certain selectivity and response/recovery time. [ABSTRACT FROM AUTHOR]