This paper describes the effect of the composition of the oxide films on the properties of electrodes Ti/M<sub>x</sub>Ti<sub>y</sub>Sn<sub>z</sub>O<sub>2</sub> (M = Ir o...This paper describes the effect of the composition of the oxide films on the properties of electrodes Ti/M<sub>x</sub>Ti<sub>y</sub>Sn<sub>z</sub>O<sub>2</sub> (M = Ir or Ru) prepared by the polymeric precursor method. XRD studies showed that the anodes are formed by solid solutions. The electrodes containing IrO<sub>2</sub> exhibit lower activity for the oxygen evolution reaction. The doping of the electrode surface with SnO<sub>2</sub> improves the catalytic properties of the anodes. However, it should be held in appropriate compositions, because the change in the atomic ratio of this element shows a marked effect on the stability of the oxides. Electrode Ti/Ir<sub>0.2</sub>Ti<sub>0.3</sub>Sn<sub>0.5</sub>O<sub>2</sub> has lower lifetime, i.e. 6 hours. The 20% decrease in the stoichiometric amount of SnO<sub>2</sub> increases the time to a value above 70 hours, as observed for Ti/Ir<sub>0.3</sub>Ti<sub>0.4</sub>Sn<sub>0.3</sub>O<sub>2</sub>. Electrode Ti/Ru<sub>0.3</sub>Ti<sub>0.4</sub>Sn<sub>0.3</sub>O<sub>2</sub> shows lifetime of 11 hours;therefore IrO<sub>2</sub> is more stable than RuO<sub>2</sub> under the conditions investigated. These results suggest that electrode Ti/Ir<sub>0.3</sub>Ti<sub>0.4</sub>Sn<sub>0.3</sub>O<sub>2</sub> is promising for different applications, such as water electrolysis, capacitors and organic electrosynthesis.展开更多
In the current work, LaNiO3 perovskite was synthesized using the polymeric precursor method. The materials were thermally treated at 300°C for 2 hours, subsequently supported on alumina or zirconia and finally ca...In the current work, LaNiO3 perovskite was synthesized using the polymeric precursor method. The materials were thermally treated at 300°C for 2 hours, subsequently supported on alumina or zirconia and finally calcined at 800°C for 4 hours. The resulting samples were characterized by X-ray diffraction, thermogravimetry, BET surface area and thermo-programmed reduction. Steam reforming reactions were carried out at 750°C and 6 bar during 4 hours using a pilot reactor under a H2O:CH4 ratio of 2.5. The mass of catalysts was about 5.7 g. X-ray diffraction patterns confirmed the formation of the perovskite structure in all samples prepared. The results also showed that lanthanum nickelate was more efficient when supported on alumina than zirconia. Finally, it was observed that the methane conversion was approximately 94% and the selectivity to hydrogen was about 70%. In all cases low selectivity to CO and CO2 was verified.展开更多
In the present work, the hybrid catalyst films of TiO2/CuO containing up to 10% in mol of copper were deposited onto glass surface. Precursor solutions were obtained by citrate precursor method. Films were porous and ...In the present work, the hybrid catalyst films of TiO2/CuO containing up to 10% in mol of copper were deposited onto glass surface. Precursor solutions were obtained by citrate precursor method. Films were porous and the average particle size was 20 nm determined by FEG-SEM analysis. The photocatalytic activities of these films were studied using Rhodamine B as a target compound in a fixed bed reactor developed in our laboratory and UV lamp. It was observed that the addition of copper to TiO2 increased significantly its photocatalytic activity during the oxidation of Rhodamine B. The degradation exceeded 90% within 48 hours of irradiation compared to 38% when pure TiO2 was used. Moreover, there was a reduction in the particles band gap energy when compared to that of pure TiO2. These results indicate that the TiO2/CuO films are promising catalysts for the development of fixed bed reactors to be used to treat effluents containing azo dyes.展开更多
This work presents a study on the synthesis of LaNixCo1-xO3 perovskites via complex precursor methods. Perovskite oxides with the composition LaNixCo1-xO3 were synthesized by chelating precursor and polymeric precurso...This work presents a study on the synthesis of LaNixCo1-xO3 perovskites via complex precursor methods. Perovskite oxides with the composition LaNixCo1-xO3 were synthesized by chelating precursor and polymeric precursor methods using nickel and/or cobalt nitrates, lanthanum nitrate, ethylene glycol, citric acid, and EDTA as starting source. The obtained perovskite were characterized by thermogravimetric analysis, infrared spectroscopy, X-ray diffraction and the morphology of the samples were investigated by N2 adsorption experiments and average medium particle size. TG curves and FTIR spectra were particularly useful in establishing of the optimal calcination temperature of the precursor powders. X-ray diffraction patterns revealed the formation of the perovskite structure in all samples prepared by both synthesis method and after calcinations at 700℃. The results showed that the preparation method resulted in oxides with the intended structure. The specific surface area values were influenced by preparation method.展开更多
Layered double hydroxides(LDHs)are widely used owing to their unique alternating anionic and cationic layered twodimensional(2D)structures.However,studies on the preparation of 2D LDH nanosheets with uniform thickness...Layered double hydroxides(LDHs)are widely used owing to their unique alternating anionic and cationic layered twodimensional(2D)structures.However,studies on the preparation of 2D LDH nanosheets with uniform thickness and their photodetectors are limited.In this study,two novel ultrathin LDH(Ca-In and Ca-Al LDH)nanosheets are peeled off from precursor bimetallic phosphides through the original precursor method.Both Ca-In and Ca-Al LDH nanosheets demonstrate a uniform thickness distribution with an average thickness of 3–4 nm,micron-level lateral sizes,and moderate bandgap.Owing to its broad light absorption range,hydrophilicity,and stability,Ca-In and Ca-Al LDH nanosheets are applied for the first time in photoelectrochemical photodetectors,realizing a wide range of light detection from ultraviolet(365 nm)to visible light(635 nm).Moreover,the fabricated photodetectors exhibit excellent cycle stability,and the average photocurrent density shows no reduction after 70 days.Therefore,this study provides an effective method to prepare 2D Ca-In and Ca-Al LDH nanosheets with uniform thickness and photoelectric application prospects.展开更多
SnO2 and Sb-doped SnO2 particles were synthesized using the polymeric precursor method with different Sn salt precursors： SnCl2.2H2O, SnCl4.5H20, or Sn citrate. Sb2O3 was used as the precursor of Sb, and the molar ra...SnO2 and Sb-doped SnO2 particles were synthesized using the polymeric precursor method with different Sn salt precursors： SnCl2.2H2O, SnCl4.5H20, or Sn citrate. Sb2O3 was used as the precursor of Sb, and the molar ratio of nsn：nsb was held constant. FTIR and TGA/DTA were used to examine the influence of the Sn precursor on the formation and thermal decomposition of the Sn and Sn-Sb complexes. The calcination products obtained from heating the Sn and Sn-Sb complexes at 500℃ in air were analyzed using XRD and TEM analysis. The results revealed that the SnO2 and Sb-doped SnO2 formation temperatures depended on the nature of the Sn precursor. The calcination products were found to be SnO2 and Sb-doped SnO2 particles, which crystallized in a tetragonal cassiterite structure with a highly preferred （110） planar orientation. The Sn precursor and the presence of Sb in the SnO2 matrix strongly influenced the crystallinity and lattice parameters.展开更多
Based on the borehole strainmeter recordings immediately before the strong earthquakes （Ms〉7.5） during the period from 2001 to 2005 observed at the Taian observation station, Shandong Province, the authors make a s...Based on the borehole strainmeter recordings immediately before the strong earthquakes （Ms〉7.5） during the period from 2001 to 2005 observed at the Taian observation station, Shandong Province, the authors make a systematic and objective examination of the precursor waves of the quakes. The effects of Earth tides with periods larger than 128 min are eliminated through high-pass filtering; and atmospheric-pressure inferences are removed by linear regression. The 2-128 min signals are then separated into six frequency bands by employing the wavelet method. Results indicate that the wavelet method is capable of picking out information of weak variations in the signals. According to the characteristics of the ＇precursor waves＇ obtained from wavelet transformation, the method of overrun ratio analysis is put forward for examination. All the detailed components of the wavelets have been analyzed. For the time series of the overrun rate in all these components, statisitical calculation has been made for the slopes of fit curves, and mean values and standard deviations were obtained and positive-negative slope ratios were analyzed. The three statistical data show that ＇precursor waves＇ are not widely recorded by borehole strainmeter within 15 days before remote strong earthquakes.展开更多
The predictability of El Ni-o-Southern Oscillation (ENSO) has been an important area of study for years. Searching for the optimal precursor (OPR) of ENSO occurrence is an effective way to understand its predictabilit...The predictability of El Ni-o-Southern Oscillation (ENSO) has been an important area of study for years. Searching for the optimal precursor (OPR) of ENSO occurrence is an effective way to understand its predictability. The CNOP (conditional nonlinear optimal perturbation), one of the most effective ways to depict the predictability of ENSO, is adopted to study the optimal sea surface temperature (SST) precursors (SST-OPRs) of ENSO in the IOCAS ICM (intermediate coupled model developed at the Institute of Oceanology, Chinese Academy of Sciences). To seek the SST-OPRs of ENSO in the ICM, non-ENSO events simulated by the ICM are chosen as the basic state. Then, the gradient-definition-based method (GD method) is employed to solve the CNOP for different initial months of the basic years to obtain the SSTOPRs. The experimental results show that the obtained SST-OPRs present a positive anomaly signal in the western-central equatorial Pacific, and obvious differences exist in the patterns between the different seasonal SST-OPRs along the equatorial western-central Pacific, showing seasonal dependence to some extent. Furthermore, the non-El Ni-o events can eventually evolve into El Ni-o events when the SST-OPRs are superimposed on the corresponding seasons;the peaks of the Ni-o3.4 index occur at the ends of the years, which is consistent with the evolution of the real El Ni-o. These results show that the GD method is an effective way to obtain SST-OPRs for ENSO events in the ICM. Moreover, the OPRs for ENSO depicted using the GD method provide useful information for finding the early signal of ENSO in the ICM.展开更多
文摘This paper describes the effect of the composition of the oxide films on the properties of electrodes Ti/M<sub>x</sub>Ti<sub>y</sub>Sn<sub>z</sub>O<sub>2</sub> (M = Ir or Ru) prepared by the polymeric precursor method. XRD studies showed that the anodes are formed by solid solutions. The electrodes containing IrO<sub>2</sub> exhibit lower activity for the oxygen evolution reaction. The doping of the electrode surface with SnO<sub>2</sub> improves the catalytic properties of the anodes. However, it should be held in appropriate compositions, because the change in the atomic ratio of this element shows a marked effect on the stability of the oxides. Electrode Ti/Ir<sub>0.2</sub>Ti<sub>0.3</sub>Sn<sub>0.5</sub>O<sub>2</sub> has lower lifetime, i.e. 6 hours. The 20% decrease in the stoichiometric amount of SnO<sub>2</sub> increases the time to a value above 70 hours, as observed for Ti/Ir<sub>0.3</sub>Ti<sub>0.4</sub>Sn<sub>0.3</sub>O<sub>2</sub>. Electrode Ti/Ru<sub>0.3</sub>Ti<sub>0.4</sub>Sn<sub>0.3</sub>O<sub>2</sub> shows lifetime of 11 hours;therefore IrO<sub>2</sub> is more stable than RuO<sub>2</sub> under the conditions investigated. These results suggest that electrode Ti/Ir<sub>0.3</sub>Ti<sub>0.4</sub>Sn<sub>0.3</sub>O<sub>2</sub> is promising for different applications, such as water electrolysis, capacitors and organic electrosynthesis.
基金The authors wish to acknowledge RECAT-Petrobras,Rede de Hidrogenio-MCTANP for their financial support and scholarship grants.
文摘In the current work, LaNiO3 perovskite was synthesized using the polymeric precursor method. The materials were thermally treated at 300°C for 2 hours, subsequently supported on alumina or zirconia and finally calcined at 800°C for 4 hours. The resulting samples were characterized by X-ray diffraction, thermogravimetry, BET surface area and thermo-programmed reduction. Steam reforming reactions were carried out at 750°C and 6 bar during 4 hours using a pilot reactor under a H2O:CH4 ratio of 2.5. The mass of catalysts was about 5.7 g. X-ray diffraction patterns confirmed the formation of the perovskite structure in all samples prepared. The results also showed that lanthanum nickelate was more efficient when supported on alumina than zirconia. Finally, it was observed that the methane conversion was approximately 94% and the selectivity to hydrogen was about 70%. In all cases low selectivity to CO and CO2 was verified.
基金FAPESP,FAPEMIG,CAPES and CNPq for the financial support.
文摘In the present work, the hybrid catalyst films of TiO2/CuO containing up to 10% in mol of copper were deposited onto glass surface. Precursor solutions were obtained by citrate precursor method. Films were porous and the average particle size was 20 nm determined by FEG-SEM analysis. The photocatalytic activities of these films were studied using Rhodamine B as a target compound in a fixed bed reactor developed in our laboratory and UV lamp. It was observed that the addition of copper to TiO2 increased significantly its photocatalytic activity during the oxidation of Rhodamine B. The degradation exceeded 90% within 48 hours of irradiation compared to 38% when pure TiO2 was used. Moreover, there was a reduction in the particles band gap energy when compared to that of pure TiO2. These results indicate that the TiO2/CuO films are promising catalysts for the development of fixed bed reactors to be used to treat effluents containing azo dyes.
文摘This work presents a study on the synthesis of LaNixCo1-xO3 perovskites via complex precursor methods. Perovskite oxides with the composition LaNixCo1-xO3 were synthesized by chelating precursor and polymeric precursor methods using nickel and/or cobalt nitrates, lanthanum nitrate, ethylene glycol, citric acid, and EDTA as starting source. The obtained perovskite were characterized by thermogravimetric analysis, infrared spectroscopy, X-ray diffraction and the morphology of the samples were investigated by N2 adsorption experiments and average medium particle size. TG curves and FTIR spectra were particularly useful in establishing of the optimal calcination temperature of the precursor powders. X-ray diffraction patterns revealed the formation of the perovskite structure in all samples prepared by both synthesis method and after calcinations at 700℃. The results showed that the preparation method resulted in oxides with the intended structure. The specific surface area values were influenced by preparation method.
基金supported by the State Key Program of the National Natural Science Foundation of China(No.52130303)the National Key R&D Program of China(No.2016YFA0202302)+1 种基金the National Natural Science Foundation of China(Nos.52103093 and 52173078)the China Postdoctoral Science Foundation(No.2021M702424).
文摘Layered double hydroxides(LDHs)are widely used owing to their unique alternating anionic and cationic layered twodimensional(2D)structures.However,studies on the preparation of 2D LDH nanosheets with uniform thickness and their photodetectors are limited.In this study,two novel ultrathin LDH(Ca-In and Ca-Al LDH)nanosheets are peeled off from precursor bimetallic phosphides through the original precursor method.Both Ca-In and Ca-Al LDH nanosheets demonstrate a uniform thickness distribution with an average thickness of 3–4 nm,micron-level lateral sizes,and moderate bandgap.Owing to its broad light absorption range,hydrophilicity,and stability,Ca-In and Ca-Al LDH nanosheets are applied for the first time in photoelectrochemical photodetectors,realizing a wide range of light detection from ultraviolet(365 nm)to visible light(635 nm).Moreover,the fabricated photodetectors exhibit excellent cycle stability,and the average photocurrent density shows no reduction after 70 days.Therefore,this study provides an effective method to prepare 2D Ca-In and Ca-Al LDH nanosheets with uniform thickness and photoelectric application prospects.
文摘SnO2 and Sb-doped SnO2 particles were synthesized using the polymeric precursor method with different Sn salt precursors： SnCl2.2H2O, SnCl4.5H20, or Sn citrate. Sb2O3 was used as the precursor of Sb, and the molar ratio of nsn：nsb was held constant. FTIR and TGA/DTA were used to examine the influence of the Sn precursor on the formation and thermal decomposition of the Sn and Sn-Sb complexes. The calcination products obtained from heating the Sn and Sn-Sb complexes at 500℃ in air were analyzed using XRD and TEM analysis. The results revealed that the SnO2 and Sb-doped SnO2 formation temperatures depended on the nature of the Sn precursor. The calcination products were found to be SnO2 and Sb-doped SnO2 particles, which crystallized in a tetragonal cassiterite structure with a highly preferred （110） planar orientation. The Sn precursor and the presence of Sb in the SnO2 matrix strongly influenced the crystallinity and lattice parameters.
基金supported by National Natural Science Foundation of China (40374011)Joint Seismological Science Foundation of China (1040037)
文摘Based on the borehole strainmeter recordings immediately before the strong earthquakes （Ms〉7.5） during the period from 2001 to 2005 observed at the Taian observation station, Shandong Province, the authors make a systematic and objective examination of the precursor waves of the quakes. The effects of Earth tides with periods larger than 128 min are eliminated through high-pass filtering; and atmospheric-pressure inferences are removed by linear regression. The 2-128 min signals are then separated into six frequency bands by employing the wavelet method. Results indicate that the wavelet method is capable of picking out information of weak variations in the signals. According to the characteristics of the ＇precursor waves＇ obtained from wavelet transformation, the method of overrun ratio analysis is put forward for examination. All the detailed components of the wavelets have been analyzed. For the time series of the overrun rate in all these components, statisitical calculation has been made for the slopes of fit curves, and mean values and standard deviations were obtained and positive-negative slope ratios were analyzed. The three statistical data show that ＇precursor waves＇ are not widely recorded by borehole strainmeter within 15 days before remote strong earthquakes.
基金supported by the Fundamental Research Funds for the Central Universities (Grant No. 22120190 207)the Strategic Priority Research Program of the Chinese Academy of Sciences (Grant No. XDA19060102)+4 种基金the National Key Research and Development Program of China (Grant No. 2017YFC1404102(2017YFC1404100))the National Programme on Global Change and Air-Sea Interaction (Grant No. GASIIPOVAI-06)National Natural Science Foundation of China (Grant Nos. 41690122(41690120), 41490644(41490640), 414210 05)the Taishan Scholarshipthe Institute of Oceanology, Chinese Academy of Sciences, for providing technical support for IOCAS ICM
文摘The predictability of El Ni-o-Southern Oscillation (ENSO) has been an important area of study for years. Searching for the optimal precursor (OPR) of ENSO occurrence is an effective way to understand its predictability. The CNOP (conditional nonlinear optimal perturbation), one of the most effective ways to depict the predictability of ENSO, is adopted to study the optimal sea surface temperature (SST) precursors (SST-OPRs) of ENSO in the IOCAS ICM (intermediate coupled model developed at the Institute of Oceanology, Chinese Academy of Sciences). To seek the SST-OPRs of ENSO in the ICM, non-ENSO events simulated by the ICM are chosen as the basic state. Then, the gradient-definition-based method (GD method) is employed to solve the CNOP for different initial months of the basic years to obtain the SSTOPRs. The experimental results show that the obtained SST-OPRs present a positive anomaly signal in the western-central equatorial Pacific, and obvious differences exist in the patterns between the different seasonal SST-OPRs along the equatorial western-central Pacific, showing seasonal dependence to some extent. Furthermore, the non-El Ni-o events can eventually evolve into El Ni-o events when the SST-OPRs are superimposed on the corresponding seasons;the peaks of the Ni-o3.4 index occur at the ends of the years, which is consistent with the evolution of the real El Ni-o. These results show that the GD method is an effective way to obtain SST-OPRs for ENSO events in the ICM. Moreover, the OPRs for ENSO depicted using the GD method provide useful information for finding the early signal of ENSO in the ICM.
