Potassium promoted iron–zinc catalysts prepared by co-precipitation method(C–Fe–Zn/K),solvothermal method(S–Fe–Zn/K)and hydrothermal method(H–Fe–Zn/K)could selectively convert CO_2to light olefins,respectively....Potassium promoted iron–zinc catalysts prepared by co-precipitation method(C–Fe–Zn/K),solvothermal method(S–Fe–Zn/K)and hydrothermal method(H–Fe–Zn/K)could selectively convert CO_2to light olefins,respectively.The physicochemical properties of the obtained catalysts were determined by SEM,N_2physisorption,XRD,H_2-TPR,CO_2-TPD and XPS measurements.The results demonstrated that preparation methods had great influences on the morphology,phase structures,reduction and adsorption behavior,and hence the catalytic performance of the catalysts.The samples prepared by hydrothermal and co-precipitation method generated small uniform particles and led to lower specific surface area.In contrast,microspheres with larger specific surface area were formed by self-assembly of nanosheets using solvothermal method.ZnFe_2O_4was the only detectable phase in the fresh C–2Fe–1Zn/K,S–3Fe–1Zn/K and S–2Fe–1Zn/K samples.ZnFe_2O_4and ZnO co-existed with increasing Zncontent in S–1Fe–1Zn/K sample,while ZnO and Fe_2O_3could be observed over H–2Fe–1Zn/K sample.All the used samples contained Fe_3O_4,ZnO and Fe_5C_2.The peak intensity of ZnO was strong in the AR-H–2Fe–1Zn/K sample while it was the lowest in the AR-C–2Fe–1Zn/K sample after reaction.The formation of ZnFe_2O_4increased the interaction between iron and zinc for C–2Fe–1Zn/K and S–Fe–Zn/K samples,causing easier reduction of Fe_2O_3to Fe_3O_4.The surface basicity of the sample prepared by co-precipitation method was much more than that of the other two methods.During CO_2hydrogenation,all the catalysts showed good activity and olefin selectivity.The CO selectivity was increased with increasing Zncontent over S–Fe–Zn/K samples.H–2Fe–1Zn/K catalyst preferred to the production of C_5^+hydrocarbons.CO_2conversion of 54.76%and C_2~=–C_4~=contents of 57.38%were obtained on C–2Fe–1Zn/K sample,respectively.展开更多
NaTaONcatalysts were synthesized by a hydrothermal（H） and a solid-state（S） methods in this study.The H-and S-NaTaONsamples were characterized by X-ray diffraction（XRD）, scanning electron microscopy（SEM）, trans...NaTaONcatalysts were synthesized by a hydrothermal（H） and a solid-state（S） methods in this study.The H-and S-NaTaONsamples were characterized by X-ray diffraction（XRD）, scanning electron microscopy（SEM）, transmission electron microscopy（TEM）, UV–visible（UV–vis） diffuse reflectance spectroscopy, and photoluminescence（PL） spectroscopy. The XRD patterns of the H-and S-samples showed peaks indexed to the pure phase of perovskite NaTaOand minor peaks assignable to TaNat various synthesis temperatures. Substitution of oxygen by nitrogen ions causes the light absorption of the H-and S-NaTaONsamples to be extended to the 600–650 nm region, thus making the samples visible-light active. The NaTaONsamples exhibited photocatalytic activity for Hand Oevolution from aqueous methanol and silver nitrate solutions under visible-light irradiation. The UV–vis and PL spectra of the Hand S-catalysts revealed the presence of cationic vacancies and reduced metallic species, which acted as recombination centers. These results demonstrated that the preparation method plays a critical role in the formation of defect states, thereby governing the photocatalytic activity of the NaTaONcatalysts.展开更多
K4Ce2Nb10O30 ultrafine powders were prepared by stearic acid method (SAM). The obtained products were analyzed by X-ray diffraction, transmission electron microscopy, energy dispersive X-ray spectrometry, scanning ele...K4Ce2Nb10O30 ultrafine powders were prepared by stearic acid method (SAM). The obtained products were analyzed by X-ray diffraction, transmission electron microscopy, energy dispersive X-ray spectrometry, scanning electron microscopy and UV-visible absorption spectra. XRD patterns revealed that K4Ce2Nb10O30 powders treated at 900 oC for 2 h presented tetragonal structure without the presence of deleterious phases. Furthermore, the K4Ce2Nb10O30 prepared by SAM had considerable activity under visible light irradiation.展开更多
The measurements of light yield of PbWO<sub>4</sub> crystals with normal methods may haverelatively large errors because the crystals have a low light yield.Therefore,a single photoelec-tron method with no...The measurements of light yield of PbWO<sub>4</sub> crystals with normal methods may haverelatively large errors because the crystals have a low light yield.Therefore,a single photoelec-tron method with normal radioactive sources is proposed and the measurements for severalPbWO<sub>4</sub> samples produced by Beijing Glass Research Institute are reported.展开更多
We report a new and simple preparation method of the visible light responsive Titanium dioxide (TiO2) photocatalytic films using sol-gel method and ultraviolet light (UV) irradiation. Proposed films were prepared on f...We report a new and simple preparation method of the visible light responsive Titanium dioxide (TiO2) photocatalytic films using sol-gel method and ultraviolet light (UV) irradiation. Proposed films were prepared on fused silica plates using titanium tetra-isopropoxide, urea, 2-methoxyethanol, water and UV irradiation. The 650°C-annealed films were carbon-containing anatase type TiO2, not carbon-doped ones. The prepared films absorbed visible light with wavelengths longer than 400 nm. Also, organic dyes were effectively photodegradated by visible light irradiation in the presence of these films.展开更多
基金Supports by the National Natural Science Foundation of China(21666030,21366025)National First-rate Discipline Construction Project of Ningxia(NXYLXK2017A04)
文摘Potassium promoted iron–zinc catalysts prepared by co-precipitation method(C–Fe–Zn/K),solvothermal method(S–Fe–Zn/K)and hydrothermal method(H–Fe–Zn/K)could selectively convert CO_2to light olefins,respectively.The physicochemical properties of the obtained catalysts were determined by SEM,N_2physisorption,XRD,H_2-TPR,CO_2-TPD and XPS measurements.The results demonstrated that preparation methods had great influences on the morphology,phase structures,reduction and adsorption behavior,and hence the catalytic performance of the catalysts.The samples prepared by hydrothermal and co-precipitation method generated small uniform particles and led to lower specific surface area.In contrast,microspheres with larger specific surface area were formed by self-assembly of nanosheets using solvothermal method.ZnFe_2O_4was the only detectable phase in the fresh C–2Fe–1Zn/K,S–3Fe–1Zn/K and S–2Fe–1Zn/K samples.ZnFe_2O_4and ZnO co-existed with increasing Zncontent in S–1Fe–1Zn/K sample,while ZnO and Fe_2O_3could be observed over H–2Fe–1Zn/K sample.All the used samples contained Fe_3O_4,ZnO and Fe_5C_2.The peak intensity of ZnO was strong in the AR-H–2Fe–1Zn/K sample while it was the lowest in the AR-C–2Fe–1Zn/K sample after reaction.The formation of ZnFe_2O_4increased the interaction between iron and zinc for C–2Fe–1Zn/K and S–Fe–Zn/K samples,causing easier reduction of Fe_2O_3to Fe_3O_4.The surface basicity of the sample prepared by co-precipitation method was much more than that of the other two methods.During CO_2hydrogenation,all the catalysts showed good activity and olefin selectivity.The CO selectivity was increased with increasing Zncontent over S–Fe–Zn/K samples.H–2Fe–1Zn/K catalyst preferred to the production of C_5^+hydrocarbons.CO_2conversion of 54.76%and C_2~=–C_4~=contents of 57.38%were obtained on C–2Fe–1Zn/K sample,respectively.
基金the financial support from the Ministry of Science and Technology,Taiwan(MOST 104-2218-E-033-006-MY2)
文摘NaTaONcatalysts were synthesized by a hydrothermal（H） and a solid-state（S） methods in this study.The H-and S-NaTaONsamples were characterized by X-ray diffraction（XRD）, scanning electron microscopy（SEM）, transmission electron microscopy（TEM）, UV–visible（UV–vis） diffuse reflectance spectroscopy, and photoluminescence（PL） spectroscopy. The XRD patterns of the H-and S-samples showed peaks indexed to the pure phase of perovskite NaTaOand minor peaks assignable to TaNat various synthesis temperatures. Substitution of oxygen by nitrogen ions causes the light absorption of the H-and S-NaTaONsamples to be extended to the 600–650 nm region, thus making the samples visible-light active. The NaTaONsamples exhibited photocatalytic activity for Hand Oevolution from aqueous methanol and silver nitrate solutions under visible-light irradiation. The UV–vis and PL spectra of the Hand S-catalysts revealed the presence of cationic vacancies and reduced metallic species, which acted as recombination centers. These results demonstrated that the preparation method plays a critical role in the formation of defect states, thereby governing the photocatalytic activity of the NaTaONcatalysts.
基金Project supported by the National Natural Science Foundation of China (20872051) "Zijin Star" of NJUST
文摘K4Ce2Nb10O30 ultrafine powders were prepared by stearic acid method (SAM). The obtained products were analyzed by X-ray diffraction, transmission electron microscopy, energy dispersive X-ray spectrometry, scanning electron microscopy and UV-visible absorption spectra. XRD patterns revealed that K4Ce2Nb10O30 powders treated at 900 oC for 2 h presented tetragonal structure without the presence of deleterious phases. Furthermore, the K4Ce2Nb10O30 prepared by SAM had considerable activity under visible light irradiation.
基金The project supported by the Science Foundation of Beijingthe Foundation of Science College of Tsinghua University
文摘The measurements of light yield of PbWO<sub>4</sub> crystals with normal methods may haverelatively large errors because the crystals have a low light yield.Therefore,a single photoelec-tron method with normal radioactive sources is proposed and the measurements for severalPbWO<sub>4</sub> samples produced by Beijing Glass Research Institute are reported.
文摘We report a new and simple preparation method of the visible light responsive Titanium dioxide (TiO2) photocatalytic films using sol-gel method and ultraviolet light (UV) irradiation. Proposed films were prepared on fused silica plates using titanium tetra-isopropoxide, urea, 2-methoxyethanol, water and UV irradiation. The 650°C-annealed films were carbon-containing anatase type TiO2, not carbon-doped ones. The prepared films absorbed visible light with wavelengths longer than 400 nm. Also, organic dyes were effectively photodegradated by visible light irradiation in the presence of these films.
