Theoretical investigation has shown a simple reaction water turbine would perform better when it spins faster. And for the simple reaction turbine water turbine to spin faster under constant water head, its diameter s...Theoretical investigation has shown a simple reaction water turbine would perform better when it spins faster. And for the simple reaction turbine water turbine to spin faster under constant water head, its diameter should be smaller. This paper reports on a performance analysis based on the experimental data collected from different performance tests carried on two simple reaction water turbine prototypes. Two new designs of simple reaction water turbines and their manufacturing methods are reported. The two turbines under investigation have different rotor diameters Φ 0.243 m and Φ 0.122 m. In case of the simple reaction water turbine the water enters into the turbine axially and exits tangentially through nozzles located on the outer periphery of the turbine. Further this paper will discuss the performance characteristics of stationary turbine i.e. zero power produced and performance characteristics of turbine producing power. It was found that rotor diameter affects the maximum rotational speed of the simple reaction turbine for constant supply head. It was also found that faster the turbine spins its performance improves. The two turbines were tested between supply head range of 1 m to 4 m.展开更多
The water gas shift(WGS) reaction is a standard reaction that is widely used in industrial hydrogen production and removal of carbon monoxide. The improved catalytic performance of WGS reaction also contributes to amm...The water gas shift(WGS) reaction is a standard reaction that is widely used in industrial hydrogen production and removal of carbon monoxide. The improved catalytic performance of WGS reaction also contributes to ammonia synthesis and other reactions. Advanced catalysts have been developed for both high and low-temperature reactions and are widely used in industry. In recent years, supported metal nanoparticle catalysts have been researched due to their high metal utilization. Low-temperature catalysts have shown promising results, including high selectivity, high shift rates, and higher activity potential. Additionally, significant progress has been made in removing trace CO through the redox reaction in electrolytic cell. This paper reviews the development of WGS reaction catalysts, including the reaction mechanism, catalyst design, and innovative research methods. The catalyst plays a crucial role in the WGS reaction, and this paper provides an instant of catalyst design under different conditions. The progress of catalysts is closely related to the development of advanced characterization techniques.Furthermore, modifying the catalyst surface to enhance activity and significantly increase reaction kinetics is a current research direction. This review goals to stimulate a better understanding of catalyst design, performance optimization, and driving mechanisms, leading to further progress in this field.展开更多
Bi-functional electrocatalysts for acid overall water splitting reactions are crucial but still challenging to the development of proton exchange membrane water electrolysis.Herein,an efficient bi-functional catalyst ...Bi-functional electrocatalysts for acid overall water splitting reactions are crucial but still challenging to the development of proton exchange membrane water electrolysis.Herein,an efficient bi-functional catalyst of Ir/MoS_(2) nanoflowers(Ir/MoS_(2) NFs) catalyst was reported for acidic water electrolysis which can be constructed by coupling three-dimensionally interconnected MoS_(2) NFs with ultrafine Ir nanoparticles.A more suitable adsorption ability for the H* and *OOH intermediates was revealed,where the Ir sites were proposed as the main active center and MoS_(2) promoted the charge relocation to electronically modify the interfacial structure.The significant interfacial charge redistribution between the MoS_(2) NFs and the Ir active sites synergistically induced excellent catalytic activity and stability for the water electrolysis reaction.Specifically,the catalyst required overpotentials of 270 and 35 mV to reach a kinetic current density of 10 mA cm^(-2)for OER and HER,respectively,loading on the glass carbon electrode,with high catalytic kinetics,stability,and catalytic efficiency.A two-electrode system constructed by Ir/MoS_(2) NFs drove 10 mA cm^(-2)at a cell voltage of 1.55 V,about 70 mV lower than that of the commercial Pt/C||IrO_(2) system.In addition,partial surface oxidation of Ir nanoparticles to generate high-valent Ir species was also found significant to accelerate OER.The enhanced catalytic performance was attributed to the strong metal-support interaction in the Ir/MoS_(2) NFs catalyst system that changed the electronic structure of Ir metal and promoted the synergistic catalytic effect between Ir and MoS_(2) NFs.The work presented a novel platform of Ir-catalyst for proton exchange membrane water electrolysis.展开更多
Osmotic water alters the physicochemical properties and internal structures of limestone.This issue is particularly critical in tunnel construction across mountainous regions with aquifers,where pressurized groundwate...Osmotic water alters the physicochemical properties and internal structures of limestone.This issue is particularly critical in tunnel construction across mountainous regions with aquifers,where pressurized groundwater can destabilize the limestone-based surrounding rock.Thus,systematic research into the physicochemical properties and pore structure changes in the limestone under pressurized water is essential.Additionally,it is essential to develop an interpretable mathematical model to accurately depict how pressurized osmotic water weakens limestone.In this research,a specialized device was designed to simulate the process of osmotic laminar flow within limestone.Then,four main tests were conducted:mass loss,acoustic emission(AE),mercury intrusion porosimetry(MIP),and fluorescence analysis.Experimental results gained from tests led to the development of a“Particle-pore throat-water film”model.Proposed model explains water-induced physicochemical and pore changes in limestone under osmotic pressure and reveals evolutionary mechanisms as pressure increases.Based on experimental results and model,we found that osmotic pressure not only alters limestone composition but also affects pore throats larger than 0.1μm.Furthermore,osmotic pressure expands pore throats,enhancing pore structure uniformity,interconnectivity,and permeability.These effects are observed at a threshold of 7.5 MPa,where cohesive forces within the mineral lattice are surpassed,leading to the breakdown of erosion-resistant layer and a significant increase in hydrochemical erosion.展开更多
The Ni-CeO2 catalysts with different Ni contents were prepared by a co-precipitation method and used for Reverse Water Gas Shift （RWGS） reaction. 2wt.%Ni-CeO2 showed excellent catalytic performance in terms of activ...The Ni-CeO2 catalysts with different Ni contents were prepared by a co-precipitation method and used for Reverse Water Gas Shift （RWGS） reaction. 2wt.%Ni-CeO2 showed excellent catalytic performance in terms of activity, selectivity, and stability for RWGS reaction. Characterizations of the catalyst samples were conducted by XRD and TPR. The results indicated that, in Ni-CeO2 catalysts, there were three kinds of nickel, nickel ions in ceria lattice, highly dispersed NiO and bulk NiO. Oxygen vacancies were formed in CeO2 lattice due to the incorporation of Ni^2＋ ions into ceria lattice. Oxygen vacancies formed in ceria lattice and highly dispersed Ni were key active components for RWGS, and bulk Ni was key active component for methanation of CO2.展开更多
In reverse water gas shift （RWGS） reaction COa is converted to CO which in turn can be used to pro- duce beneficial chemicals such as methanol. In the present study, Mo/AlaO3, Fe/AlaO3 and Fe-Mo/Al2O3 catalysts were...In reverse water gas shift （RWGS） reaction COa is converted to CO which in turn can be used to pro- duce beneficial chemicals such as methanol. In the present study, Mo/AlaO3, Fe/AlaO3 and Fe-Mo/Al2O3 catalysts were synthesised using impregnation method. The structures of catalysts were studied using X-ray diffraction （XRD）, Brunauer-Emmett-Teller （BET） method, inductively coupled plasma atomic emission spectrometer （ICP-AES）, temperature programmed reduction （H2-TPR）, CO chemisorption, energy dispersive X-ray （EDX） and scanning electron microscopy （SEM） techniques. Kinetic properties of all catalysts were investigated in a batch re- actor for RWGS reaction. The results indicated that Mo existence in structure of Fe-Mo/AlzO3 catalyst enhances its activity as compared to Fe/AlaO3. This enhancement is probably due to better Fe dispersion and smaller particle size of Fe species. Stability test of Fe-Mo/AlzO3 catalyst was carried out in a fixed bed reactor and a high CO yield for 60 h of time on stream was demonstrated. Fez（MoO4）3 phase was found in the structures of fresh and used catalysts. TPR results also indicate that Fez（MoO4）3 phase has low reducibility, therefore the Fe2（MoO4）3 phase significantly inhibits the reduction of the remaining Fe oxides in the catalyst, resulted in high stability of Fe-Mo/Al2O3 catalyst. Overall, this study introduces Fe-Mo/Al2O3 as a novel catalyst with high CO yield, almost no by-products and fairly stable for RWGS reaction.展开更多
In this paper .the change of the crystalline phases in hardened magnesium oxychloride cement (MOC) paste in mater was analyzed by XRD. It was developed that the reaction products 5 phase or 3 phase of MOC are instable...In this paper .the change of the crystalline phases in hardened magnesium oxychloride cement (MOC) paste in mater was analyzed by XRD. It was developed that the reaction products 5 phase or 3 phase of MOC are instable in water and can be changed into Mg(OH)2 by the action of water, which causes the content of 5 phase or 3 phase to be less and less,the content of Mg(OH)2 to be more and more and the strength to be the lower the lower,after hardended MOC paste was immersed in water. The change of 5 pliase and 3 phase into Mg(OH)2 is not a dissolve process, but a hydrolysis process. The hydrolysis products of 5 phase and 3 phase are Mg(OH)2 precipitation and soluble Cl-,AIg+ ions and H2O. The hydrolysis is sponta-neous thermodynamically and its chemical kinatic equation is C = C,,e-k Thus .it is suggested that only by enhancing the stability of 5 phase or 3 phase in water and preventing 5 phase or 3 phase from the hydrolyzing can the water resistance of MOC be improved well.展开更多
Water jet thruster, which is a marine system that creates a jet of water for propulsion, has several advantages such as low noise, good anti-cavitation characteristics and maneuvering characteristics. The reaction thr...Water jet thruster, which is a marine system that creates a jet of water for propulsion, has several advantages such as low noise, good anti-cavitation characteristics and maneuvering characteristics. The reaction thrust characteristics of water jet for conical nozzles directly determine the speed of autonomous underwater vehicles （AUV）. Theoretical, numerical and experimental studies have been, carried out to investigate the effects of the nozzle geometries as well as inlet conditions on the reaction thrust of water jet in this paper. The experimental results show that： 1） the reaction thrust is proportional to inlet pressure, the square of flow rate and 2/3 power exponent of input power; 2） the diameter of cylinder column for conical nozzle has great influence on the reaction thrust characteristics; 3） the best values of the half cone angle and the cylinder column length exist to make the reaction thrust coefficient to reach the maximum under the same inlet conditions. Those provide a basis for nozzles design and have significant value, especially for developing high performance and efficiency water jet propulsion unit.展开更多
The water gas shift reaction is of vital significance for the generation and transition of energy due to the application in hydrogen production and industries such as ammonia synthesis and fuel cells.The influence of ...The water gas shift reaction is of vital significance for the generation and transition of energy due to the application in hydrogen production and industries such as ammonia synthesis and fuel cells.The influence of support doping and bimetallic alloying on the catalytic performance of Pt/Ce O_(2)-based nanocatalysts in water gas shift reaction was reported in this work.Various lanthanide ions and 3d transition metals were respectively introduced into the Ce O_(2)support or Pt to form Pt/Ce O_(2):Ln(Ln=La,Nd,Gd,Tb,Yb)and Pt M/Ce O_(2)(M=Fe,Co,Ni)nanocatalysts.The sample of Pt/Ce O_(2):Tb showed the highest activity(TOF at 200℃=0.051 s^(-1))among the Pt/Ce O_(2):Ln and the undoped Pt/Ce O_(2)catalysts.Besides,the sample of Pt Fe/Ce O_(2)exhibited the highest activity(TOF at 200℃=0.12 s^(-1))among Pt M/Ce O_(2)catalysts.The results of the multiple characterizations indicated that the catalytic activity of Pt/Ce O_(2):Ln catalysts was closely correlated with the amount of oxygen vacancies in doped ceria support.However,the different activity of Pt M/Ce O_(2)bimetallic catalysts was owing to the various Pt oxidation states of the bimetals dispersed on ceria.The study of the reaction pathway indicated that both the samples of Pt/Ce O_(2)and Pt/Ce O_(2):Tb catalyzed the reaction through the formate pathway,and the enhanced activity of the latter derived from the increased concentration of oxygen vacancies along with promoted water dissociation.As for the sample of Pt Fe/Ce O_(2),its catalytic mechanism was the carboxyl route with a higher reaction rate due to the moderate valence of Pt along with improved CO activation.展开更多
Photoelectrochemical(PEC) water splitting using solar energy has attracted great attention for generation of renewable hydrogen with less carbon footprint, while there are enormous challenges that still remain for imp...Photoelectrochemical(PEC) water splitting using solar energy has attracted great attention for generation of renewable hydrogen with less carbon footprint, while there are enormous challenges that still remain for improving solar energy water splitting efficiency, due to limited light harvesting, energy loss associated to fast recombination of photogenerated charge carriers, as well as electrode degradation. This overview focuses on the recent development about catalyst nanomaterials and nanostructures in different PEC water splitting systems. As photoanode, Au nanoparticle-decorated TiO_2 nanowire electrodes exhibited enhanced photoactivity in both the UV and the visible regions due to surface plasmon resonance of Au and showed the largest photocurrent generation of up to 710 nm. Pt/Cd S/CGSe electrodes were developed as photocathode. With the role of p–n heterojunction, the photoelectrode showed high stability and evolved hydrogen continuously for more than 10 days. Further, in the Z-scheme system(Bi_2S_3/TNA as photoanode and Pt/Si PVC as photocathode at the same time), a self-bias(open-circuit voltage Voc= 0.766 V) was formed between two photoelectrodes, which could facilitate photogenerated charge transfers and enhance the photoelectrochemical performance, and which might provide new hints for PEC water splitting. Meanwhile, the existing problems and prospective solutions have also been reviewed.展开更多
Various copper promoted Au/ZnO-CuO catalysts with different atomic ratios of Cu to Zn prepared by means of co-precipitation were tested for the low temperature water-gas shift（WGS） reaction. The catalytic activity o...Various copper promoted Au/ZnO-CuO catalysts with different atomic ratios of Cu to Zn prepared by means of co-precipitation were tested for the low temperature water-gas shift（WGS） reaction. The catalytic activity of the catalyst depends largely on the ratio of Cu to Zn. The addition of an appropriate amount of copper can considerably improve both the catalytic activity and the stability of the catalyst in comparison with those of copper-free Au/ZnO cata- lysts. The enhanced reducibility of copper oxide in the Au/ZnO-CuO ternary-component catalysts, which was confirmed by H2-TPR, may be related to the high activity and stability of the catalyst for the low temperature WGS reaction.展开更多
The surface reaction of Co 3Ti alloys (with and without Fe) with water vapor was investigated by using Auger electron spectroscopy (AES). The results showed that the rate of the surface reaction is much lower in Co 21...The surface reaction of Co 3Ti alloys (with and without Fe) with water vapor was investigated by using Auger electron spectroscopy (AES). The results showed that the rate of the surface reaction is much lower in Co 21 5Ti 3Fe alloy as compared with Co 3Ti (Co 23Ti) alloy. The surface reaction of Co 21 5Ti 3Fe alloy with water vapor saturates at exposure of 2×10 -3 Pa·s, but it does not saturate even at 0 1 Pa·s exposure for Co 3Ti alloy without Fe. The results also indicated that the kinetic of the surface reaction of Co 21 5Ti 3Fe with water vapor is much smaller than that of Co 3Ti at the same exposure. All the above results illustrate that the suppression of environmental embrittlement by addition of Fe to Co 3Ti alloy is attributed to its reduction of the surface reaction kinetics with water vapor.展开更多
The performance of La2-x M x CuO4 perovskites （where M=Ce,Ca or Sr） as catalysts for the water-gas shift reaction was investigated at 290℃ and 360℃.The catalysts were characterized by EDS,XRD,N2 adsorption-desorpt...The performance of La2-x M x CuO4 perovskites （where M=Ce,Ca or Sr） as catalysts for the water-gas shift reaction was investigated at 290℃ and 360℃.The catalysts were characterized by EDS,XRD,N2 adsorption-desorption,XPS and XANES.The XRD results showed that all the perovskites exhibited a single phase （the presence of perovskite structure）,suggesting the incorporation of metals in the perovskite structure.The XPS and XANES results showed the presence of Cu2＋ on the surface.The perovskites that exhibited the best catalytic performance were La 2 x Ce x CuO 4 perovskites,with CO conversions of 85% 90%.Moreover,these perovskites have higher surface areas and larger amounts of Cu on the surface.And Ce has a higher filled energy level than the other metals,increasing the energy of the valence band of Ce and providing more electrons for the reaction.Besides,the La1.80Ca0.20CuO4 perovskite showed a good catalytic performance.展开更多
Based on formate and direct oxidation mechanisms,three Langmuir-Hinshelwood-Hougen-Watson （LHHW） kinetic models of the water-gasshift （WGS） reaction over a nano-structured iron catalyst under Fischer-Tropsch synth...Based on formate and direct oxidation mechanisms,three Langmuir-Hinshelwood-Hougen-Watson （LHHW） kinetic models of the water-gasshift （WGS） reaction over a nano-structured iron catalyst under Fischer-Tropsch synthesis （FTS） reaction conditions were derived and compared with those over the conventional catalyst.The conventional and nanostructured Fe/Cu/La/Si catalysts were prepared by co-precipitation of Fe and Cu nitrates in aqueous media and water-oil micro-emulsion,respectively.The WGS kinetic data were measured by experiments over a wide range of reaction conditions and comparisons were also made for various rate equations.WGS rate expressions based on the formate mechanism with the assumption that the formation of formate is rate determining step were found to be the best.展开更多
A zero-dimensional model to simulate a nano-pulse-discharged bubble in water was developed. The model consists of gas and liquid phases corresponding to the inside and outside of the bubble, respectively. The diffusio...A zero-dimensional model to simulate a nano-pulse-discharged bubble in water was developed. The model consists of gas and liquid phases corresponding to the inside and outside of the bubble, respectively. The diffusions of chemical species from the gas to the liquid phase through the bubble interface was also investigated. The initial gas is Ar, but includes a little H20 and 02 in the bubble. The time evolution of the OH concentration in the liquid phase was mainly investigated as an important species for water treatment. It was shown that OH was generated in the bubble and then diffused into the liquid. With the application of a continuous nano-pulse discharge, more OH radicals were generated as the frequency increased at a low voltage for a given power consumption.展开更多
A method for quantitative evaluating the enhancement of the rate of Type Ⅱ photosensitized oxidation by D_2O was suggested. The effect of substrate concentration on this process was also discussed.
An acid catalyzed oxa-Pictet-Spengler reaction‘on water leading to the synthesis of a variety of l-aryl-6,7-dimethoxyisochro-mans is described.The aqueous chemistry is a much cleaner,efficient,cheaper and simple meth...An acid catalyzed oxa-Pictet-Spengler reaction‘on water leading to the synthesis of a variety of l-aryl-6,7-dimethoxyisochro-mans is described.The aqueous chemistry is a much cleaner,efficient,cheaper and simple method for synthesis.The scope of reactions was extended to thia-Pictet-Spengler reaction to afford the some isothiochromans.展开更多
The epoxidation reaction of propylene and hydrogen peroxide with zeolite catalyst containing titaniumsilicalite (TS-1)has been studied, and the reaction in the mixed solvent of water/methanol has been discussed. It is...The epoxidation reaction of propylene and hydrogen peroxide with zeolite catalyst containing titaniumsilicalite (TS-1)has been studied, and the reaction in the mixed solvent of water/methanol has been discussed. It is shown that the selective of epoxidation propylene decreases while the selective of propylene glycol increases, when the water content increases in the mixed solvent of methanol/water.展开更多
Thermal decomposition of formic acid on SiO2, CeO2 and γ-Al2O3 was studied as an elementary step of reverse water–gas shit reaction（RWGS） over supported Au catalysts. γ-Al2O3 showed the highest CO selectivity amo...Thermal decomposition of formic acid on SiO2, CeO2 and γ-Al2O3 was studied as an elementary step of reverse water–gas shit reaction（RWGS） over supported Au catalysts. γ-Al2O3 showed the highest CO selectivity among the tested oxides in the decomposition of formic acid. Infrared spectroscopy showed the formation of four formate species on γ-Al2O3： three η~1-type and one μ~2-type species, and these formates decomposed to CO at 473 K or higher. Au-loaded γ-Al2O3 samples were prepared by a depositionprecipitation method and used as catalysts for RWGS. The supported Au catalyst gave CO with high selectivity over 99% from CO2 and H2, which is attributed to the formation of formates on Au and subsequent decomposition to CO on γ-Al2O3.展开更多
It is represented the review about the effect of low doses of ionized radiation on different types of biological objects (Japanese quail embryos, Aspergillus niger, Spirostomum ambiguum Ehrbg., mezenchim stem cells of...It is represented the review about the effect of low doses of ionized radiation on different types of biological objects (Japanese quail embryos, Aspergillus niger, Spirostomum ambiguum Ehrbg., mezenchim stem cells of mice bone brain, dry seeds of the highest plants, blood lymphocytes of pilots and cosmonauts) and water medium. In model experiments under the chronic ionized radiation in doses comparable with the doses of ionized radiation inside the orbital space stations and during the flight in interplanetary space was shown alike with morphological deviations (Japanese quail embryos, Aspergillus niger), the phenomenon of radiation hormezis (Aspergillus niger, mezenchim stem cells), the increasing of the germination of seeds, the decreasing of spontaneous motion activity of spirostoms and DNA damage, chromosome aberrations and the increased radio-sensitivity to adding radiation load in blood lymphocytes. These data testified the fact that the definite factor of ionized radiation effect is the changing of water medium state. Thus under the interplanetary cosmic flight and long stay on the orbit in the region of magnetosphere the studying kinds of radiation first effected on the water medium of organism as a result morpho-functional structures were changed.展开更多
文摘Theoretical investigation has shown a simple reaction water turbine would perform better when it spins faster. And for the simple reaction turbine water turbine to spin faster under constant water head, its diameter should be smaller. This paper reports on a performance analysis based on the experimental data collected from different performance tests carried on two simple reaction water turbine prototypes. Two new designs of simple reaction water turbines and their manufacturing methods are reported. The two turbines under investigation have different rotor diameters Φ 0.243 m and Φ 0.122 m. In case of the simple reaction water turbine the water enters into the turbine axially and exits tangentially through nozzles located on the outer periphery of the turbine. Further this paper will discuss the performance characteristics of stationary turbine i.e. zero power produced and performance characteristics of turbine producing power. It was found that rotor diameter affects the maximum rotational speed of the simple reaction turbine for constant supply head. It was also found that faster the turbine spins its performance improves. The two turbines were tested between supply head range of 1 m to 4 m.
基金financially supported by the National Natural Science Foundation of China (22279118, 22279117, 22075254,31901272)the Top-Notch Talent Program of Henan Agricultural University (30501034)。
文摘The water gas shift(WGS) reaction is a standard reaction that is widely used in industrial hydrogen production and removal of carbon monoxide. The improved catalytic performance of WGS reaction also contributes to ammonia synthesis and other reactions. Advanced catalysts have been developed for both high and low-temperature reactions and are widely used in industry. In recent years, supported metal nanoparticle catalysts have been researched due to their high metal utilization. Low-temperature catalysts have shown promising results, including high selectivity, high shift rates, and higher activity potential. Additionally, significant progress has been made in removing trace CO through the redox reaction in electrolytic cell. This paper reviews the development of WGS reaction catalysts, including the reaction mechanism, catalyst design, and innovative research methods. The catalyst plays a crucial role in the WGS reaction, and this paper provides an instant of catalyst design under different conditions. The progress of catalysts is closely related to the development of advanced characterization techniques.Furthermore, modifying the catalyst surface to enhance activity and significantly increase reaction kinetics is a current research direction. This review goals to stimulate a better understanding of catalyst design, performance optimization, and driving mechanisms, leading to further progress in this field.
基金supported by the National Natural Science Foundation of China (21972124, 22272148)the Priority Academic Program Development of Jiangsu Higher Education Institution。
文摘Bi-functional electrocatalysts for acid overall water splitting reactions are crucial but still challenging to the development of proton exchange membrane water electrolysis.Herein,an efficient bi-functional catalyst of Ir/MoS_(2) nanoflowers(Ir/MoS_(2) NFs) catalyst was reported for acidic water electrolysis which can be constructed by coupling three-dimensionally interconnected MoS_(2) NFs with ultrafine Ir nanoparticles.A more suitable adsorption ability for the H* and *OOH intermediates was revealed,where the Ir sites were proposed as the main active center and MoS_(2) promoted the charge relocation to electronically modify the interfacial structure.The significant interfacial charge redistribution between the MoS_(2) NFs and the Ir active sites synergistically induced excellent catalytic activity and stability for the water electrolysis reaction.Specifically,the catalyst required overpotentials of 270 and 35 mV to reach a kinetic current density of 10 mA cm^(-2)for OER and HER,respectively,loading on the glass carbon electrode,with high catalytic kinetics,stability,and catalytic efficiency.A two-electrode system constructed by Ir/MoS_(2) NFs drove 10 mA cm^(-2)at a cell voltage of 1.55 V,about 70 mV lower than that of the commercial Pt/C||IrO_(2) system.In addition,partial surface oxidation of Ir nanoparticles to generate high-valent Ir species was also found significant to accelerate OER.The enhanced catalytic performance was attributed to the strong metal-support interaction in the Ir/MoS_(2) NFs catalyst system that changed the electronic structure of Ir metal and promoted the synergistic catalytic effect between Ir and MoS_(2) NFs.The work presented a novel platform of Ir-catalyst for proton exchange membrane water electrolysis.
基金funded by the National Key R&D Program of China(2023YFC3806800).
文摘Osmotic water alters the physicochemical properties and internal structures of limestone.This issue is particularly critical in tunnel construction across mountainous regions with aquifers,where pressurized groundwater can destabilize the limestone-based surrounding rock.Thus,systematic research into the physicochemical properties and pore structure changes in the limestone under pressurized water is essential.Additionally,it is essential to develop an interpretable mathematical model to accurately depict how pressurized osmotic water weakens limestone.In this research,a specialized device was designed to simulate the process of osmotic laminar flow within limestone.Then,four main tests were conducted:mass loss,acoustic emission(AE),mercury intrusion porosimetry(MIP),and fluorescence analysis.Experimental results gained from tests led to the development of a“Particle-pore throat-water film”model.Proposed model explains water-induced physicochemical and pore changes in limestone under osmotic pressure and reveals evolutionary mechanisms as pressure increases.Based on experimental results and model,we found that osmotic pressure not only alters limestone composition but also affects pore throats larger than 0.1μm.Furthermore,osmotic pressure expands pore throats,enhancing pore structure uniformity,interconnectivity,and permeability.These effects are observed at a threshold of 7.5 MPa,where cohesive forces within the mineral lattice are surpassed,leading to the breakdown of erosion-resistant layer and a significant increase in hydrochemical erosion.
基金Project supported by the National Natural Science Foundation of China (20476079)
文摘The Ni-CeO2 catalysts with different Ni contents were prepared by a co-precipitation method and used for Reverse Water Gas Shift （RWGS） reaction. 2wt.%Ni-CeO2 showed excellent catalytic performance in terms of activity, selectivity, and stability for RWGS reaction. Characterizations of the catalyst samples were conducted by XRD and TPR. The results indicated that, in Ni-CeO2 catalysts, there were three kinds of nickel, nickel ions in ceria lattice, highly dispersed NiO and bulk NiO. Oxygen vacancies were formed in CeO2 lattice due to the incorporation of Ni^2＋ ions into ceria lattice. Oxygen vacancies formed in ceria lattice and highly dispersed Ni were key active components for RWGS, and bulk Ni was key active component for methanation of CO2.
基金Supported by the Iranian Nano Technology Initiative Council and Petroleum University of Technology
文摘In reverse water gas shift （RWGS） reaction COa is converted to CO which in turn can be used to pro- duce beneficial chemicals such as methanol. In the present study, Mo/AlaO3, Fe/AlaO3 and Fe-Mo/Al2O3 catalysts were synthesised using impregnation method. The structures of catalysts were studied using X-ray diffraction （XRD）, Brunauer-Emmett-Teller （BET） method, inductively coupled plasma atomic emission spectrometer （ICP-AES）, temperature programmed reduction （H2-TPR）, CO chemisorption, energy dispersive X-ray （EDX） and scanning electron microscopy （SEM） techniques. Kinetic properties of all catalysts were investigated in a batch re- actor for RWGS reaction. The results indicated that Mo existence in structure of Fe-Mo/AlzO3 catalyst enhances its activity as compared to Fe/AlaO3. This enhancement is probably due to better Fe dispersion and smaller particle size of Fe species. Stability test of Fe-Mo/AlzO3 catalyst was carried out in a fixed bed reactor and a high CO yield for 60 h of time on stream was demonstrated. Fez（MoO4）3 phase was found in the structures of fresh and used catalysts. TPR results also indicate that Fez（MoO4）3 phase has low reducibility, therefore the Fe2（MoO4）3 phase significantly inhibits the reduction of the remaining Fe oxides in the catalyst, resulted in high stability of Fe-Mo/Al2O3 catalyst. Overall, this study introduces Fe-Mo/Al2O3 as a novel catalyst with high CO yield, almost no by-products and fairly stable for RWGS reaction.
文摘In this paper .the change of the crystalline phases in hardened magnesium oxychloride cement (MOC) paste in mater was analyzed by XRD. It was developed that the reaction products 5 phase or 3 phase of MOC are instable in water and can be changed into Mg(OH)2 by the action of water, which causes the content of 5 phase or 3 phase to be less and less,the content of Mg(OH)2 to be more and more and the strength to be the lower the lower,after hardended MOC paste was immersed in water. The change of 5 pliase and 3 phase into Mg(OH)2 is not a dissolve process, but a hydrolysis process. The hydrolysis products of 5 phase and 3 phase are Mg(OH)2 precipitation and soluble Cl-,AIg+ ions and H2O. The hydrolysis is sponta-neous thermodynamically and its chemical kinatic equation is C = C,,e-k Thus .it is suggested that only by enhancing the stability of 5 phase or 3 phase in water and preventing 5 phase or 3 phase from the hydrolyzing can the water resistance of MOC be improved well.
基金supported by the National Natural Science Foundation of China(Grant No.50775081)the National High Technology Research and Development Program of China(863 Program,Grant No.2006AA09Z238)
文摘Water jet thruster, which is a marine system that creates a jet of water for propulsion, has several advantages such as low noise, good anti-cavitation characteristics and maneuvering characteristics. The reaction thrust characteristics of water jet for conical nozzles directly determine the speed of autonomous underwater vehicles （AUV）. Theoretical, numerical and experimental studies have been, carried out to investigate the effects of the nozzle geometries as well as inlet conditions on the reaction thrust of water jet in this paper. The experimental results show that： 1） the reaction thrust is proportional to inlet pressure, the square of flow rate and 2/3 power exponent of input power; 2） the diameter of cylinder column for conical nozzle has great influence on the reaction thrust characteristics; 3） the best values of the half cone angle and the cylinder column length exist to make the reaction thrust coefficient to reach the maximum under the same inlet conditions. Those provide a basis for nozzles design and have significant value, especially for developing high performance and efficiency water jet propulsion unit.
基金financial support from the National Natural Science Foundation of China(21832001 and 21771009)the Beijing National Laboratory for Molecular Sciences(BNLMSCXXM-202104)。
文摘The water gas shift reaction is of vital significance for the generation and transition of energy due to the application in hydrogen production and industries such as ammonia synthesis and fuel cells.The influence of support doping and bimetallic alloying on the catalytic performance of Pt/Ce O_(2)-based nanocatalysts in water gas shift reaction was reported in this work.Various lanthanide ions and 3d transition metals were respectively introduced into the Ce O_(2)support or Pt to form Pt/Ce O_(2):Ln(Ln=La,Nd,Gd,Tb,Yb)and Pt M/Ce O_(2)(M=Fe,Co,Ni)nanocatalysts.The sample of Pt/Ce O_(2):Tb showed the highest activity(TOF at 200℃=0.051 s^(-1))among the Pt/Ce O_(2):Ln and the undoped Pt/Ce O_(2)catalysts.Besides,the sample of Pt Fe/Ce O_(2)exhibited the highest activity(TOF at 200℃=0.12 s^(-1))among Pt M/Ce O_(2)catalysts.The results of the multiple characterizations indicated that the catalytic activity of Pt/Ce O_(2):Ln catalysts was closely correlated with the amount of oxygen vacancies in doped ceria support.However,the different activity of Pt M/Ce O_(2)bimetallic catalysts was owing to the various Pt oxidation states of the bimetals dispersed on ceria.The study of the reaction pathway indicated that both the samples of Pt/Ce O_(2)and Pt/Ce O_(2):Tb catalyzed the reaction through the formate pathway,and the enhanced activity of the latter derived from the increased concentration of oxygen vacancies along with promoted water dissociation.As for the sample of Pt Fe/Ce O_(2),its catalytic mechanism was the carboxyl route with a higher reaction rate due to the moderate valence of Pt along with improved CO activation.
基金supported by the EU-China EcoFuel project(FP7,246772)from the European Commission
文摘Photoelectrochemical(PEC) water splitting using solar energy has attracted great attention for generation of renewable hydrogen with less carbon footprint, while there are enormous challenges that still remain for improving solar energy water splitting efficiency, due to limited light harvesting, energy loss associated to fast recombination of photogenerated charge carriers, as well as electrode degradation. This overview focuses on the recent development about catalyst nanomaterials and nanostructures in different PEC water splitting systems. As photoanode, Au nanoparticle-decorated TiO_2 nanowire electrodes exhibited enhanced photoactivity in both the UV and the visible regions due to surface plasmon resonance of Au and showed the largest photocurrent generation of up to 710 nm. Pt/Cd S/CGSe electrodes were developed as photocathode. With the role of p–n heterojunction, the photoelectrode showed high stability and evolved hydrogen continuously for more than 10 days. Further, in the Z-scheme system(Bi_2S_3/TNA as photoanode and Pt/Si PVC as photocathode at the same time), a self-bias(open-circuit voltage Voc= 0.766 V) was formed between two photoelectrodes, which could facilitate photogenerated charge transfers and enhance the photoelectrochemical performance, and which might provide new hints for PEC water splitting. Meanwhile, the existing problems and prospective solutions have also been reviewed.
文摘Various copper promoted Au/ZnO-CuO catalysts with different atomic ratios of Cu to Zn prepared by means of co-precipitation were tested for the low temperature water-gas shift（WGS） reaction. The catalytic activity of the catalyst depends largely on the ratio of Cu to Zn. The addition of an appropriate amount of copper can considerably improve both the catalytic activity and the stability of the catalyst in comparison with those of copper-free Au/ZnO cata- lysts. The enhanced reducibility of copper oxide in the Au/ZnO-CuO ternary-component catalysts, which was confirmed by H2-TPR, may be related to the high activity and stability of the catalyst for the low temperature WGS reaction.
文摘The surface reaction of Co 3Ti alloys (with and without Fe) with water vapor was investigated by using Auger electron spectroscopy (AES). The results showed that the rate of the surface reaction is much lower in Co 21 5Ti 3Fe alloy as compared with Co 3Ti (Co 23Ti) alloy. The surface reaction of Co 21 5Ti 3Fe alloy with water vapor saturates at exposure of 2×10 -3 Pa·s, but it does not saturate even at 0 1 Pa·s exposure for Co 3Ti alloy without Fe. The results also indicated that the kinetic of the surface reaction of Co 21 5Ti 3Fe with water vapor is much smaller than that of Co 3Ti at the same exposure. All the above results illustrate that the suppression of environmental embrittlement by addition of Fe to Co 3Ti alloy is attributed to its reduction of the surface reaction kinetics with water vapor.
文摘The performance of La2-x M x CuO4 perovskites （where M=Ce,Ca or Sr） as catalysts for the water-gas shift reaction was investigated at 290℃ and 360℃.The catalysts were characterized by EDS,XRD,N2 adsorption-desorption,XPS and XANES.The XRD results showed that all the perovskites exhibited a single phase （the presence of perovskite structure）,suggesting the incorporation of metals in the perovskite structure.The XPS and XANES results showed the presence of Cu2＋ on the surface.The perovskites that exhibited the best catalytic performance were La 2 x Ce x CuO 4 perovskites,with CO conversions of 85% 90%.Moreover,these perovskites have higher surface areas and larger amounts of Cu on the surface.And Ce has a higher filled energy level than the other metals,increasing the energy of the valence band of Ce and providing more electrons for the reaction.Besides,the La1.80Ca0.20CuO4 perovskite showed a good catalytic performance.
文摘Based on formate and direct oxidation mechanisms,three Langmuir-Hinshelwood-Hougen-Watson （LHHW） kinetic models of the water-gasshift （WGS） reaction over a nano-structured iron catalyst under Fischer-Tropsch synthesis （FTS） reaction conditions were derived and compared with those over the conventional catalyst.The conventional and nanostructured Fe/Cu/La/Si catalysts were prepared by co-precipitation of Fe and Cu nitrates in aqueous media and water-oil micro-emulsion,respectively.The WGS kinetic data were measured by experiments over a wide range of reaction conditions and comparisons were also made for various rate equations.WGS rate expressions based on the formate mechanism with the assumption that the formation of formate is rate determining step were found to be the best.
基金supported partially by Japan Society for the Promotion of Science(JSPS)KAKENHI(No.26249015)
文摘A zero-dimensional model to simulate a nano-pulse-discharged bubble in water was developed. The model consists of gas and liquid phases corresponding to the inside and outside of the bubble, respectively. The diffusions of chemical species from the gas to the liquid phase through the bubble interface was also investigated. The initial gas is Ar, but includes a little H20 and 02 in the bubble. The time evolution of the OH concentration in the liquid phase was mainly investigated as an important species for water treatment. It was shown that OH was generated in the bubble and then diffused into the liquid. With the application of a continuous nano-pulse discharge, more OH radicals were generated as the frequency increased at a low voltage for a given power consumption.
文摘A method for quantitative evaluating the enhancement of the rate of Type Ⅱ photosensitized oxidation by D_2O was suggested. The effect of substrate concentration on this process was also discussed.
文摘An acid catalyzed oxa-Pictet-Spengler reaction‘on water leading to the synthesis of a variety of l-aryl-6,7-dimethoxyisochro-mans is described.The aqueous chemistry is a much cleaner,efficient,cheaper and simple method for synthesis.The scope of reactions was extended to thia-Pictet-Spengler reaction to afford the some isothiochromans.
文摘The epoxidation reaction of propylene and hydrogen peroxide with zeolite catalyst containing titaniumsilicalite (TS-1)has been studied, and the reaction in the mixed solvent of water/methanol has been discussed. It is shown that the selective of epoxidation propylene decreases while the selective of propylene glycol increases, when the water content increases in the mixed solvent of methanol/water.
文摘Thermal decomposition of formic acid on SiO2, CeO2 and γ-Al2O3 was studied as an elementary step of reverse water–gas shit reaction（RWGS） over supported Au catalysts. γ-Al2O3 showed the highest CO selectivity among the tested oxides in the decomposition of formic acid. Infrared spectroscopy showed the formation of four formate species on γ-Al2O3： three η~1-type and one μ~2-type species, and these formates decomposed to CO at 473 K or higher. Au-loaded γ-Al2O3 samples were prepared by a depositionprecipitation method and used as catalysts for RWGS. The supported Au catalyst gave CO with high selectivity over 99% from CO2 and H2, which is attributed to the formation of formates on Au and subsequent decomposition to CO on γ-Al2O3.
文摘It is represented the review about the effect of low doses of ionized radiation on different types of biological objects (Japanese quail embryos, Aspergillus niger, Spirostomum ambiguum Ehrbg., mezenchim stem cells of mice bone brain, dry seeds of the highest plants, blood lymphocytes of pilots and cosmonauts) and water medium. In model experiments under the chronic ionized radiation in doses comparable with the doses of ionized radiation inside the orbital space stations and during the flight in interplanetary space was shown alike with morphological deviations (Japanese quail embryos, Aspergillus niger), the phenomenon of radiation hormezis (Aspergillus niger, mezenchim stem cells), the increasing of the germination of seeds, the decreasing of spontaneous motion activity of spirostoms and DNA damage, chromosome aberrations and the increased radio-sensitivity to adding radiation load in blood lymphocytes. These data testified the fact that the definite factor of ionized radiation effect is the changing of water medium state. Thus under the interplanetary cosmic flight and long stay on the orbit in the region of magnetosphere the studying kinds of radiation first effected on the water medium of organism as a result morpho-functional structures were changed.
