| In recent years,due to the advantages of high physical-chemical stability,low cost,non-toxic and high catalytic activity,spinel-type metal mixed oxide has been attracted wide research attention.Spinel-type ZnMn2O4 microstructure with various morphologies had been prepared previously,and the influence of reaction conditions onto the structure,morphology and chemical properties of ZnMn2O4 had been investigated.To achieve ZnMn2O4 functional materials with high performance,the exploration on a facile synthetic method is necessary.The work of this paper is as follows:Firstly,ZnMn2O4 photocatalysts were prepared via hydrothermal method.The structures and compositions of the catalysts were characterized by scanning electron microscope(SEM),X-ray diffraction(XRD)and UV-Vis diffuse reflectance spectra(DRS).The effects of precipitants on the composition and photocatalytic activity were discussed.The results showed that urea is a rational precipitant for pure-phase ZnMn2O4 with high activity.By using urea as precipitant,the effects of hydrothermal time and temperatures were also discussed.The optimal synthetic parameter for ZnMn2O4 photocatalysts should be the reaction time of 20 h at 180?.about 55.6%of methylene blue cab be photo-degraded when irradiated with visible light(500 W xenon lamp)for 6 hours.Secondly,ZnMn2O4 powders with porous structure were prepared by low-temperature coprecipitation method.ZnMn2O4 spherical particles consisted of nanoparticles were achieved.The pore size distribution was relatively narrow,and there was no obvious agglomeration for the particles.The specific surface area of the samples after annealed at 400 0C was 95.8 m2·g-1.For the sample annealed at 450? and 500?,the surface area is similar,indicating the thermal stability.Due to the high surface area,the sample revealed high adsorption capacity,which is benefit for the photocatalytic degradation.The electrochemical test show that ZnMn2O4 powders could be used as electrode materials for supercapacitor.Finally,the structure and electrochemical properties of manganese oxides prepared under different acid leaching times were studied when using ZnMn2O4 samples as precursors.The results show that the porous structure of ZnMn2O4 precursor can be maintained within during leaching process,and the average pore size is basically unchanged.The specific surface area increased after acid leaching.With acid leaching,the zinc content in the product decreased gradually,and the precursor was firstly transformed into spinel X-MnO2,and then transformed into ?-MnO2 with large numbers of defects.Further prolonged acid leaching time,the specific surface area and the average pore size decreased,indicating that the porous structure was destroyed.Since the acid leaching product has a large specific surface area,it exhibit high supercapacitor performance in the neutral electrolyte solution.At a current density of 0.5 A·g-1,the specific capacity of ?-MnO2 was 230 F·g-1,which is nearly 3 times higher than that of ZnMn2O4 precursor.The obtained electrode material also showed good charge and discharge cycle performance. |
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