Two-dimensional(2D)ferroelectric compounds are a special class of materials that meet the need for devices miniaturization,which can lead to a wide range of applications.Here,we investigate ferroelectric properties of...Two-dimensional(2D)ferroelectric compounds are a special class of materials that meet the need for devices miniaturization,which can lead to a wide range of applications.Here,we investigate ferroelectric properties of monolayer group-IV monochalcogenides MX(M=Sn,Ge;X=Se,Te,S)via strain engineering,and their effects with contaminated hydrogen are also discussed.GeSe,GeTe,and GeS do not go through transition up to the compressive strain of-5%,and consequently have good ferroelectric parameters for device applications that can be further improved by applying strain.According to the calculated ferroelectric properties and the band gaps of these materials,we find that their band gap can be adjusted by strain for excellent photovoltaic applications.In addition,we have determined the most stable hydrogen occupancy location in the monolayer SnS and SnTe.It reveals that H prefers to absorb on SnS and SnTe monolayers as molecules rather than atomic H.As a result,hydrogen molecules have little effect on the polarization and electronic structure of monolayer SnTe and SnS.展开更多
Replacing the oxygen evolution reaction(OER)with the anodic formaldehyde oxidation reaction(FOR)is crucial for achieving low-voltage dual-electrode hydrogen evolution.However,existing FOR catalysts face challenges suc...Replacing the oxygen evolution reaction(OER)with the anodic formaldehyde oxidation reaction(FOR)is crucial for achieving low-voltage dual-electrode hydrogen evolution.However,existing FOR catalysts face challenges such as low activity,high transition state barriers,and unclear reaction mechanisms.In this study,a three-dimensional nano-composite Cu_(2)O/Cu/Mn_(2)O_(3)heterogeneous catalyst with enhanced hydrogen spillover effect was synthesized through hydrothermal and photosensitive oxidation treatment techniques.The catalyst consists of~20 nm Cu_(2)O/Cu and 30-70 nm Mn_(2)O_(3)nanoparticles.The hydrogen spillover effect enhanced Cu_(2)O/Cu/Mn_(2)O_(3)(1:1)electrocatalyst demonstrated outstanding FOR performance,with an anode potential of only 0.128 V at a current density of 100 mA cm^(-2),significantly lower than that of the Cu_(2)O/Cu-CC catalyst(0.25 V)and the OER potential(1.726 V).Moreover,the Faraday efficiency of the Cu_(2)O/Cu/Mn_(2)O_(3)(1:1)electrocatalyst reached~100%.The electrocatalyst’s FOR performance remains stable over 50 h without decay,and its hydrogen evolution reaction(HER)performance surpasses that of Cu and MnOxelectrocatalysts.Density functional theory(DFT)calculations suggested that the Cu_(2)O/Cu/Mn_(2)O_(3)catalyst significantly lowers the energy barriers for C-H bond breaking(0.48 eV)and H-H bond formation(-0.99 eV)by promoting the hydrogen spillover effect.This study provides theoretical support for designing efficient and stable low-energy dual-electrode hydrogen evolution catalysts and validates their potential through experiments.展开更多
Hydrogen spillover effect has recently garnered a lot of attention in the field of electrocatalytic hydrogen evolution reactions.A new avenue for understanding the dynamic behavior of atomic migration in which hydroge...Hydrogen spillover effect has recently garnered a lot of attention in the field of electrocatalytic hydrogen evolution reactions.A new avenue for understanding the dynamic behavior of atomic migration in which hydrogen atoms moving on a catalyst surface was opened up by the setup of the word"hydrogen spillover."However,there is currently a dearth of thorough knowledge regarding the hydrogen spillover effect.Currently,the advancement of sophisticated characterization procedures offers progressively useful information to enhance our grasp of the hydrogen spillover effect.The understanding of material fabrication for hydrogen spillover effect has erupted.Considering these factors,we made an effort to review most of the articles published on the hydrogen spillover effect and carefully analyzed the aspect of material fabrication.All of our attention has been directed toward the molecular pathway that leads to improve hydrogen evolution reactions performance.In addition,we have attempted to elucidate the spillover paths through the utilization of DFT calculations.Furthermore,we provide some preliminary research suggestions and highlight the opportunities and obstacles that are still to be confronted in this study area.展开更多
The effects of hydrogen atoms on behaviour of low cycle fatigue of 2.25Cr-1Mo steel have been investigated in present work. The results indicate that the cyclic softening rate and low cycle fatigue life are respective...The effects of hydrogen atoms on behaviour of low cycle fatigue of 2.25Cr-1Mo steel have been investigated in present work. The results indicate that the cyclic softening rate and low cycle fatigue life are respectively increased and reduced remarkably by hydrogen atoms. In addition, hydrogen atoms make the original stress amplitude of low cycle fatigue increase, which is because of the drag effect of hydrogen atoms on the moving dislocations. Analyses using electron microscopy show that hydrogen atoms accelerate crack initiation of low cycle fatigue from inclusion and transfer the source of low cycle fatigue crack from the surface of specimen to the inclusion, which results in the marked decrease of low cycle fatigue life. The increase of cyclic softening rate for hydrogen charged specimen is due to hydrogen atoms accelerating the initiating and growing of microvoids from the secondary phase particles in the steel. The reducing of the drag effect of hydrogen atoms on moving dislocations is also helpful to the increase of the cyclic softening rate.展开更多
SiO2,α-Al2O3,γ-Al2O3,ZrO2 and CeO2 were used as supports and Ag as promoter to study their effects on Pd catalysts for selective hydrogenation of acetylene.The catalysts were prepared by impregnated synthesis and ch...SiO2,α-Al2O3,γ-Al2O3,ZrO2 and CeO2 were used as supports and Ag as promoter to study their effects on Pd catalysts for selective hydrogenation of acetylene.The catalysts were prepared by impregnated synthesis and characterized by XRD,BET and TEM.The catalytic reaction was carried out in a fixed-bed reactor.Overall,the low specific surface area supports were better to increase the ethylene selectivity at high conversion rate of acetylene.Among the four Pd catalysts on low specific surface area supports,the catalyst on low specific surface area SiO2(LSA-SiO2) retained a high ethylene selectivity even at complete conversion,while the other catalysts showed significant decrease in the selectivity at complete conversion.The performance of Pd/LSA-SiO2 was important to decrease the loss of ethylene in selective hydrogenation of trace acetylene in ethylene.Addition of Ag to Pd/LSA-SiO2 significantly decreased the formation of ethane,C4 alkenes and green oil,and improved the ethylene selectivity to 90% when Pd:Ag=1:1 and 1:3(ω).When the ratio of Pd to Ag was above 1,the activity of Pd-Ag bimetallic catalyst was similar to that of Pd monometallic catalyst,and the selectivity of ethylene increased with increasing of amount of Ag.When the ratio of Pd to Ag was below 1,the activity of bimetallic catalyst decreased with increasing of amount of Ag,while the selectivity of ethylene was kept unchanged.The optimum temperature was 200-230℃ for 0.02%(ω)Pd-0.02%(ω)Ag/LSA-SiO2 to give a high ethylene selectivity and low formation of green oil.展开更多
The effects of Sr TiO_3 on the hydrogen storage properties of MgH_2 have been studied for the first time.The onset dehydrogenation temperature of the MgH_2-10 wt% SrTiO_3 is found to be 275 ℃, which is 55 ℃ lower as...The effects of Sr TiO_3 on the hydrogen storage properties of MgH_2 have been studied for the first time.The onset dehydrogenation temperature of the MgH_2-10 wt% SrTiO_3 is found to be 275 ℃, which is 55 ℃ lower as compared to the as-milled MgH_2. The composite is able to absorb 4.3 wt% of hydrogen in 60 min instead of 1.1 wt% for the as-milled Mg H_2. Meanwhile, the composite is able to release 5.3 wt% of hydrogen in 17 min compared to 1.9 wt% by the as-milled Mg H_2 at 320 ℃. The calculated Eaof the Mg H_2-10 wt% SrTiO_3 is 109 k J/mol, which is 26.3 kJ/mol lower than the calculated Eaof the as-milled MgH_2. The Sr TiO_3 is not decomposed during the ball milling and the re/dehydrogenation processes. The catalytic effect shown by the SrTiO_3 is owing to its ability to change the physical structure of the MgH_2 particles during the ball milling process.展开更多
This paper deals with the vitiation effects of test air on the scramjet performance in the ground combustion heated facilities. The primary goal is to evaluate the effects of H2O and CO2, the two major vitiated specie...This paper deals with the vitiation effects of test air on the scramjet performance in the ground combustion heated facilities. The primary goal is to evaluate the effects of H2O and CO2, the two major vitiated species generated by combustion heater, on hydrogen-fueled supersonic combustor performance with experimental and numerical approaches. The comparative experiments in the clean air and vitiated air are conducted by using the resistance heated direct-connected facility, with the typical Mach 4 flight conditions simulated. The H2O and CO2 species with accurately controlled contents are added to the high enthalpy clean air from resistance heater, to synthesize the vitiated air of a combustion-type heater. Typically, the contents of H2O species can be varied within the range of 3.5%-30% by mole, and 3.0%-10% for CO2 species. The total temperature, total pressure, Mach number and O2 mole fraction at the combustor entrance are well-matched between the clean air and vitiated air. The combustion experiments are completed at the fuel equivalence ratios of 0.53 and 0.42 respectively. Furthermore, three-dimensional （3D） reacting flow simulations of combustor flowpath are performed to provide insight into flow field structures and combustion chemistry details that cannot resolved by experimental instruments available. Finally, the experimental data, combined with computational results, are employed to analyze the effects of H2O and CO2 vitiated air on supersonic combustion characteristics and performance. It is concluded that H2O and CO2 contaminants can significantly inhibit the combustion induced pressure rise measured from combustor wall, and the pressure profile decreases with the increasing H2O and CO2 contents in nonlinear trend; simulation results agree well with experimental data and the overall vitiation effects are captured; direct extrapolation of the results from vitiated air to predict the performance of actual flight conditions could result in over-fueling the combustor, possible inlet un-start and inappropriate combustion mode transition. The detailed analysis and discussion are presented and the research conclusions are summarized.展开更多
The effect of cathodic hydrogen charging on the tensile and constant load properties was deter- mined for an austenitic stainless steel weldment comprising a 304L steel in the solution treated condition as a base meta...The effect of cathodic hydrogen charging on the tensile and constant load properties was deter- mined for an austenitic stainless steel weldment comprising a 304L steel in the solution treated condition as a base metal and a 308L filler steel as a weld metal. Part of the 304L solution treated steel was separately given additional sensitization treatment to simulate the microstructure that would develop in the heat affected zone. Tests were performed at room temperature on notched round bar specimens. Hydrogen charging resulted in a pronounced embrittlement of the tested materials. This was manifested mainly as a considerable loss in the ductility of tensile specimens and a decrease in the time to failure and threshold stress of constant load specimens. The 308L weld metal exhibited the highest, and the 304L solution treated steel the lowest, resistance to hydrogen embrittlement. Hydrogen embrittlement was associated with the formation of strain induced martensite as well as a transition from brittle to ductile fracture morphology onwards the centre of the specimens.展开更多
The areal distribution of some elements in the rare earth bearing spheroidal phases in pure aluminium and Al-Mn alloys was studied by SIMS(secondary ion mass spectrometry).The results show that cerium,iron. silicon an...The areal distribution of some elements in the rare earth bearing spheroidal phases in pure aluminium and Al-Mn alloys was studied by SIMS(secondary ion mass spectrometry).The results show that cerium,iron. silicon and hydrogen are significantly segregated in the phases.Thus the existence of hydrogen-rich rare earth bearing eompounds is confirmed.It indicates that the rare earths have a hydrogen fixation effect in aluminium and aluminium alloys.展开更多
In this paper, we study the effects of Pr substitution on the hydrogenating process and magnetocaloric properties of La（1-x）PrxFe11.4Si1.6Hy hydrides. The powder x-ray diffraction patterns of the La1-xPrxFe11.4Si1.6...In this paper, we study the effects of Pr substitution on the hydrogenating process and magnetocaloric properties of La（1-x）PrxFe11.4Si1.6Hy hydrides. The powder x-ray diffraction patterns of the La1-xPrxFe11.4Si1.6 and its hydrides show that each of the alloys is crystallized into the single phase of cubic Na Zn13-type structure. There are hydrogen-absorbing plateaus under 0.4938 MPa and 0.4882 MPa in the absorbing curves for the La0.8Pr0.2Fe11.4Si1.6 and La0.6Pr0.4Fe11.4Si1.6 compounds. The releasing processes lag behind the absorbing process, which is obviously different from the coincidence between absorbing and releasing curves of the La Fe11.4Si1.6 compound. The remnant hydrogen content for La0.6Pr0.4Fe11.4Si1.6 is significantly more than that for La0.8Pr0.2Fe11.4Si1.6 after hydrogen desorption, indicating that more substitutions of Pr for La are beneficial to retaining more hydrogen atoms in the alloys. The values of maximum magnetic entropy change are 14.91 J/kg·K and 17.995 J/kg·K for La0.8Pr0.2Fe11.4Si1.6H0.13 and La0.6Pr0.4Fe11.4Si1.6H0.87,respectively.展开更多
The development of reliable fusion energy is one of the most important challenges in this century.The accelerated degradation of structural materials in fusion reactors caused by neutron irradiation would cause severe...The development of reliable fusion energy is one of the most important challenges in this century.The accelerated degradation of structural materials in fusion reactors caused by neutron irradiation would cause severe problems.Due to the lack of suitable fusion neutron testing facilities,we have to rely on ion irradiation experiments to test candidate materials in fusion reactors.Moreover,fusion neutron irradiation effects are accompanied by the simultaneous transmutation production of helium and hydrogen.One important method to study the He-H synergistic effects in materials is multiple simultaneous ion beams(MSIB)irradiation that has been studied for decades.To date,there is no convincing conclusion on these He-H synergistic effects among these experiments.Recently,a multiple ion beam in-situ transmission electron microscopy(TEM)analysis facility was developed in Xiamen University(XIAMEN facility),which is the first triple beam system and the only in-running in-situ irradiation facility with TEM in China.In this work,we conducted the first high-temperature triple simultaneous ion beams irradiation experiment with TEM observation using the XIAMEN facility.The responses to in-situ triple-ion beams irradiation in austenitic steel 304L SS and ferritic/martensitic steel CLF-1 were studied and compared with the results in dual-and single-ion beam(s)irradiated steels.Synergistic effects were observed in MSIB irradiated steels.Helium was found to be critical for cavity formation,while hydrogen has strong synergistic effect on increasing swelling.展开更多
The geometric and electronic properties of some hydrogenated silicon clusters in the presence of oxygen on the surface have been investigated.The density functional theory with generalized gradient approximation funct...The geometric and electronic properties of some hydrogenated silicon clusters in the presence of oxygen on the surface have been investigated.The density functional theory with generalized gradient approximation functional was applied in our calculations.By calculating the total energy,the double bond Si=O is shown to be more stable than the bridge bond Si-O-Si for large size oxidized clusters.The results of Mulliken population analysis indicate that a so-called passivation effect is enhanced by oxidization effects.From the energy band structures and density of states,we find that some localized states are induced by the p-orbital of O atom mainly and reduce the energy gaps substantially.展开更多
In this work, the morphologies and pore structures of a series of corncob-derived activated carbons and zeolite templated carbon with ultrahigh surface area were carefully investigated by SEM, HRTEM and N2-sorption ch...In this work, the morphologies and pore structures of a series of corncob-derived activated carbons and zeolite templated carbon with ultrahigh surface area were carefully investigated by SEM, HRTEM and N2-sorption characterization technologies. The high-pressure hydrogen uptake performance was analyzed using standard Pressure-Composition-Temperature apparatus in order to study the pore size effects on hydrogen uptake. These as-obtained porous carbons showed different characteristics of pore size distribution as well as specific surface area. The results indicate that the most effective pores for adsorbing hydrogen depended on the storage pressure. These ultramicropores （0.65-0.85 nm） could be the most effective pores on excess H2 uptake at 1 bar, however, micropores （0.85-2 nm） would play a more important role in excess H2 uptake at higher pressure at 77 K. At room temperature, pore size effects on H2 uptake capacity were very weak. Both specific surface area and total pore volume play more important roles than pore size for H2 uptake at room temperature, which was clearly different from that at 77 K. For applications in future, the corncob-derived activated carbons can be more available than zeolite templated carbons at 77 K. Element doping enhanced hydrogen uptake could be main research direction for improving H2 uptake capacity at room temperature.展开更多
Time-dependent density functional theory （TDDFT） and femtosecond transient absorption spectroscopy were used to investigate the photophysical properties of 2,3-dihydro-3-keto-lH- pyrido[3,2,1-kl]phenothiazine （PTZ4...Time-dependent density functional theory （TDDFT） and femtosecond transient absorption spectroscopy were used to investigate the photophysical properties of 2,3-dihydro-3-keto-lH- pyrido[3,2,1-kl]phenothiazine （PTZ4） and 3-keto-lH-pyrido[3,2,1-kl]phenothiazine （PTZ5）. The calculated results obtained from TDDFT suggest that the red-shifts of the absorption spectra of these two fluorophores in methanol are due to the formation of hydrogen-bonded complexes at the ground state. Four conformers of PTZ4 were obtained by TDDFT. The two fluorescence peaks of PTZ4 in tetrahydrofuran （THF） came from the ICT states of the four conformers. The fluorescence of PTZ4 in THF showed a dependence on the excitation wavelength because of butterfly bending. The excited state dynamics of PTZ4 in THF and methanol were obtained by transient absorption spectroscopy. The lifetime of the excited PTZ4 in methanol was 53.8 ps, and its relaxation from the LE state to the ICT state was completed within several picoseconds. The short lifetime of excited PTZ4 in methanol was due to the formation of out-of-plane model hydrogen bonds between PTZ4 and methanol at the excited state.展开更多
Cu-x-Fe-y/SiO2 catalysts were prepared using urea-assisted sol-gel method. The structure and physicochemical properties of the catalysts were characterized using N-2 adsorption-desorption, transmission electron micros...Cu-x-Fe-y/SiO2 catalysts were prepared using urea-assisted sol-gel method. The structure and physicochemical properties of the catalysts were characterized using N-2 adsorption-desorption, transmission electron microscopy, H-2-temperature-programmed reduction, powder X-ray diffraction, and X-ray photoelectron spectroscopy. Compared with monometallic Cu or Fe catalysts, the bimetallic Cu-x-Fe-y/SiO2 catalysts exhibited enhanced catalytic performance for the selective hydrogenation of diethyl malonate to 1,3-propanediol. The bimetallic catalyst with an optimal Cu/Fe atomic ratio of 2 exhibited the highest activity, which yielded 96.3% conversion to diethyl malonate and 93.3% selectivity to 1,3-propanediol under the optimal reaction conditions. Characterization results revealed that interactions between Cu and Fe contributed to the improvement of diethyl malonate conversion and selectivity to 1,3-propanediol. The X-ray photoelectron spectroscopy results revealed that the addition of appropriate amount of Fe species enhanced the reduction of Cu2+ species, thereby increasing the Cu-0 species on the surface of bimetallic catalyst. It led to a better chemisorption capacity of hydrogen and further promoted of the activation of hydrogen molecule. The ethyl acetate temperature-programmed desorption results indicated that the FeOx species provided the additional adsorption sites for substrate molecules, and they activated the C=O bond. The improved catalytic performance of bimetallic Cu-x-Fe-y/SiO2 catalyst was mainly attributed to the synergistic effect between Cu-0 and FeOx species. (C) 2016 Science Press and Dalian Institute of Chemical Physics, Chinese Academy of Sciences. Published by Elsevier B.V. and Science Press. All rights reserved.展开更多
Hydrogen purification must be done to meet the different purposes of hydrogen utilization.In the present work,it is confirmed that the catalyst Ni/CeO2 has the highest activity for total methanation(Total MET) of CO a...Hydrogen purification must be done to meet the different purposes of hydrogen utilization.In the present work,it is confirmed that the catalyst Ni/CeO2 has the highest activity for total methanation(Total MET) of CO and CO2,and is thus most suitable for hydrogen purification for ammonia synthesis.While,the catalyst Ni/ZrO2 appears the best one for selective methanation of CO(CO-SMET) in the H2-rich gas to produce clean fuel for proton exchange membrane fuel cell(PEMFC).In spite of this,the catalyst Ni/ZrO2 without adding chlorine ions as promoter is not yet capable of removing the CO in the reformate gas to below 10 ppm in a wide reaction temperature range by the way of CO-SMET.Adding chlorine ions as promoter is indeed not favorable for practical application due to its gradual loss in the catalytic reaction as proved in our previous work.Therefore,a step to decrease CO2 concentration(called as de-CO2 step) is suggested to be set prior to the CO-SMET step in this work.It is proved that such combination of de-CO2 step and CO-SMET step is efficient to achieve a deep removal of CO to below 10 ppm with a high selectivity more than 50% in a wide reaction temperature range of 220-280℃over the catalyst Ni/ZrO2 without adding chlorine ions as promoter.The combined process has potential for practical application,at least in the large-scale power plant of PEMFC.展开更多
The method of numerical simulation is used to fit the relationship between the photoconductivity in films and the illumination time. The generation and process rule of kinds of different charged defect states during i...The method of numerical simulation is used to fit the relationship between the photoconductivity in films and the illumination time. The generation and process rule of kinds of different charged defect states during illumination are revealed. It is found surprisingly that the initial photoconductivity determines directly the total account of photoconductivity degradation of sample.展开更多
Studies of direction of photoisomerization of retinal,retinonitrile,a- retinonitrile and a trienenitrile analog in different solvents with varying wave- lengths of excitation and reaction temperature led to the conclu...Studies of direction of photoisomerization of retinal,retinonitrile,a- retinonitrile and a trienenitrile analog in different solvents with varying wave- lengths of excitation and reaction temperature led to the conclusion that the well known solvent dependent photochemistry of retinoids is due to selective excitation of the hydrogen bonded species.展开更多
In this paper, hydrogen is first utilized in the study on methane coupling under nonequilibrium plasma. Results indicate that the addition of hydrogen is beneficial. to the methane coupling so as to increase the conv...In this paper, hydrogen is first utilized in the study on methane coupling under nonequilibrium plasma. Results indicate that the addition of hydrogen is beneficial. to the methane coupling so as to increase the conversion rate of methane and the yield of C2 hydrocarbon with a gradual increase in the addition of hydrogen in a certain range of proportionality. This conclusion explores a new route of hydrogenated methane coupling.展开更多
B3LYP/6 31+g( d ) calculations were performed on the hydrogen bonded complexes between substituted phenolates and HF, H 2O as well as NH 3. It was found that some properties of the non covalent complexes, inclu...B3LYP/6 31+g( d ) calculations were performed on the hydrogen bonded complexes between substituted phenolates and HF, H 2O as well as NH 3. It was found that some properties of the non covalent complexes, including the interaction energies, donor acceptor (host vip) distances, bond lengths, and vibration frequencies, could show well defined substituent effects. Thus, from the substituent studies we can not only understand the mechanism of a particular non covalent interaction better, but also easily predict the interaction energies and structures of a particular non covalent complex, which might otherwise be very hard or resource consuming to be known. This means that substituent effect is indeed a useful tool to be used in supramolecular chemistry and therefore, many valuable studies remain to be carried out.展开更多
基金the National Natural Science Foundation of China(NSFC)(Grant No.12074126)the Foundation for Innovative Research Groups of NSFC(Grant No.51621001)the Fundamental Research Funds for the Central Universities(Grant No.2020ZYGXZR076).
文摘Two-dimensional(2D)ferroelectric compounds are a special class of materials that meet the need for devices miniaturization,which can lead to a wide range of applications.Here,we investigate ferroelectric properties of monolayer group-IV monochalcogenides MX(M=Sn,Ge;X=Se,Te,S)via strain engineering,and their effects with contaminated hydrogen are also discussed.GeSe,GeTe,and GeS do not go through transition up to the compressive strain of-5%,and consequently have good ferroelectric parameters for device applications that can be further improved by applying strain.According to the calculated ferroelectric properties and the band gaps of these materials,we find that their band gap can be adjusted by strain for excellent photovoltaic applications.In addition,we have determined the most stable hydrogen occupancy location in the monolayer SnS and SnTe.It reveals that H prefers to absorb on SnS and SnTe monolayers as molecules rather than atomic H.As a result,hydrogen molecules have little effect on the polarization and electronic structure of monolayer SnTe and SnS.
基金supported by the State Key Laboratory of Materials Low-Carbon Recycling,Beijing University of Technologysponsored by the Beijing Nova Program(20240484638),China。
文摘Replacing the oxygen evolution reaction(OER)with the anodic formaldehyde oxidation reaction(FOR)is crucial for achieving low-voltage dual-electrode hydrogen evolution.However,existing FOR catalysts face challenges such as low activity,high transition state barriers,and unclear reaction mechanisms.In this study,a three-dimensional nano-composite Cu_(2)O/Cu/Mn_(2)O_(3)heterogeneous catalyst with enhanced hydrogen spillover effect was synthesized through hydrothermal and photosensitive oxidation treatment techniques.The catalyst consists of~20 nm Cu_(2)O/Cu and 30-70 nm Mn_(2)O_(3)nanoparticles.The hydrogen spillover effect enhanced Cu_(2)O/Cu/Mn_(2)O_(3)(1:1)electrocatalyst demonstrated outstanding FOR performance,with an anode potential of only 0.128 V at a current density of 100 mA cm^(-2),significantly lower than that of the Cu_(2)O/Cu-CC catalyst(0.25 V)and the OER potential(1.726 V).Moreover,the Faraday efficiency of the Cu_(2)O/Cu/Mn_(2)O_(3)(1:1)electrocatalyst reached~100%.The electrocatalyst’s FOR performance remains stable over 50 h without decay,and its hydrogen evolution reaction(HER)performance surpasses that of Cu and MnOxelectrocatalysts.Density functional theory(DFT)calculations suggested that the Cu_(2)O/Cu/Mn_(2)O_(3)catalyst significantly lowers the energy barriers for C-H bond breaking(0.48 eV)and H-H bond formation(-0.99 eV)by promoting the hydrogen spillover effect.This study provides theoretical support for designing efficient and stable low-energy dual-electrode hydrogen evolution catalysts and validates their potential through experiments.
基金supported by Brain Pool program funded by the Ministry of Science and ICT through the National Research Foundation of Korea(Grant Nos.RS-2023-00284361 and 2021R1A2C2091497)supported by the Nano&Materials Technology Development Program through the National Research Foundation of Korea(NRF)funded by Ministry of Science and ICT(RS-2024-00436563)
文摘Hydrogen spillover effect has recently garnered a lot of attention in the field of electrocatalytic hydrogen evolution reactions.A new avenue for understanding the dynamic behavior of atomic migration in which hydrogen atoms moving on a catalyst surface was opened up by the setup of the word"hydrogen spillover."However,there is currently a dearth of thorough knowledge regarding the hydrogen spillover effect.Currently,the advancement of sophisticated characterization procedures offers progressively useful information to enhance our grasp of the hydrogen spillover effect.The understanding of material fabrication for hydrogen spillover effect has erupted.Considering these factors,we made an effort to review most of the articles published on the hydrogen spillover effect and carefully analyzed the aspect of material fabrication.All of our attention has been directed toward the molecular pathway that leads to improve hydrogen evolution reactions performance.In addition,we have attempted to elucidate the spillover paths through the utilization of DFT calculations.Furthermore,we provide some preliminary research suggestions and highlight the opportunities and obstacles that are still to be confronted in this study area.
文摘The effects of hydrogen atoms on behaviour of low cycle fatigue of 2.25Cr-1Mo steel have been investigated in present work. The results indicate that the cyclic softening rate and low cycle fatigue life are respectively increased and reduced remarkably by hydrogen atoms. In addition, hydrogen atoms make the original stress amplitude of low cycle fatigue increase, which is because of the drag effect of hydrogen atoms on the moving dislocations. Analyses using electron microscopy show that hydrogen atoms accelerate crack initiation of low cycle fatigue from inclusion and transfer the source of low cycle fatigue crack from the surface of specimen to the inclusion, which results in the marked decrease of low cycle fatigue life. The increase of cyclic softening rate for hydrogen charged specimen is due to hydrogen atoms accelerating the initiating and growing of microvoids from the secondary phase particles in the steel. The reducing of the drag effect of hydrogen atoms on moving dislocations is also helpful to the increase of the cyclic softening rate.
文摘SiO2,α-Al2O3,γ-Al2O3,ZrO2 and CeO2 were used as supports and Ag as promoter to study their effects on Pd catalysts for selective hydrogenation of acetylene.The catalysts were prepared by impregnated synthesis and characterized by XRD,BET and TEM.The catalytic reaction was carried out in a fixed-bed reactor.Overall,the low specific surface area supports were better to increase the ethylene selectivity at high conversion rate of acetylene.Among the four Pd catalysts on low specific surface area supports,the catalyst on low specific surface area SiO2(LSA-SiO2) retained a high ethylene selectivity even at complete conversion,while the other catalysts showed significant decrease in the selectivity at complete conversion.The performance of Pd/LSA-SiO2 was important to decrease the loss of ethylene in selective hydrogenation of trace acetylene in ethylene.Addition of Ag to Pd/LSA-SiO2 significantly decreased the formation of ethane,C4 alkenes and green oil,and improved the ethylene selectivity to 90% when Pd:Ag=1:1 and 1:3(ω).When the ratio of Pd to Ag was above 1,the activity of Pd-Ag bimetallic catalyst was similar to that of Pd monometallic catalyst,and the selectivity of ethylene increased with increasing of amount of Ag.When the ratio of Pd to Ag was below 1,the activity of bimetallic catalyst decreased with increasing of amount of Ag,while the selectivity of ethylene was kept unchanged.The optimum temperature was 200-230℃ for 0.02%(ω)Pd-0.02%(ω)Ag/LSA-SiO2 to give a high ethylene selectivity and low formation of green oil.
基金financially supported by the Ministry of Higher Education Malaysia under the Fundamental Research Grant Scheme (FRGS 59362)
文摘The effects of Sr TiO_3 on the hydrogen storage properties of MgH_2 have been studied for the first time.The onset dehydrogenation temperature of the MgH_2-10 wt% SrTiO_3 is found to be 275 ℃, which is 55 ℃ lower as compared to the as-milled MgH_2. The composite is able to absorb 4.3 wt% of hydrogen in 60 min instead of 1.1 wt% for the as-milled Mg H_2. Meanwhile, the composite is able to release 5.3 wt% of hydrogen in 17 min compared to 1.9 wt% by the as-milled Mg H_2 at 320 ℃. The calculated Eaof the Mg H_2-10 wt% SrTiO_3 is 109 k J/mol, which is 26.3 kJ/mol lower than the calculated Eaof the as-milled MgH_2. The Sr TiO_3 is not decomposed during the ball milling and the re/dehydrogenation processes. The catalytic effect shown by the SrTiO_3 is owing to its ability to change the physical structure of the MgH_2 particles during the ball milling process.
文摘This paper deals with the vitiation effects of test air on the scramjet performance in the ground combustion heated facilities. The primary goal is to evaluate the effects of H2O and CO2, the two major vitiated species generated by combustion heater, on hydrogen-fueled supersonic combustor performance with experimental and numerical approaches. The comparative experiments in the clean air and vitiated air are conducted by using the resistance heated direct-connected facility, with the typical Mach 4 flight conditions simulated. The H2O and CO2 species with accurately controlled contents are added to the high enthalpy clean air from resistance heater, to synthesize the vitiated air of a combustion-type heater. Typically, the contents of H2O species can be varied within the range of 3.5%-30% by mole, and 3.0%-10% for CO2 species. The total temperature, total pressure, Mach number and O2 mole fraction at the combustor entrance are well-matched between the clean air and vitiated air. The combustion experiments are completed at the fuel equivalence ratios of 0.53 and 0.42 respectively. Furthermore, three-dimensional （3D） reacting flow simulations of combustor flowpath are performed to provide insight into flow field structures and combustion chemistry details that cannot resolved by experimental instruments available. Finally, the experimental data, combined with computational results, are employed to analyze the effects of H2O and CO2 vitiated air on supersonic combustion characteristics and performance. It is concluded that H2O and CO2 contaminants can significantly inhibit the combustion induced pressure rise measured from combustor wall, and the pressure profile decreases with the increasing H2O and CO2 contents in nonlinear trend; simulation results agree well with experimental data and the overall vitiation effects are captured; direct extrapolation of the results from vitiated air to predict the performance of actual flight conditions could result in over-fueling the combustor, possible inlet un-start and inappropriate combustion mode transition. The detailed analysis and discussion are presented and the research conclusions are summarized.
文摘The effect of cathodic hydrogen charging on the tensile and constant load properties was deter- mined for an austenitic stainless steel weldment comprising a 304L steel in the solution treated condition as a base metal and a 308L filler steel as a weld metal. Part of the 304L solution treated steel was separately given additional sensitization treatment to simulate the microstructure that would develop in the heat affected zone. Tests were performed at room temperature on notched round bar specimens. Hydrogen charging resulted in a pronounced embrittlement of the tested materials. This was manifested mainly as a considerable loss in the ductility of tensile specimens and a decrease in the time to failure and threshold stress of constant load specimens. The 308L weld metal exhibited the highest, and the 304L solution treated steel the lowest, resistance to hydrogen embrittlement. Hydrogen embrittlement was associated with the formation of strain induced martensite as well as a transition from brittle to ductile fracture morphology onwards the centre of the specimens.
文摘The areal distribution of some elements in the rare earth bearing spheroidal phases in pure aluminium and Al-Mn alloys was studied by SIMS(secondary ion mass spectrometry).The results show that cerium,iron. silicon and hydrogen are significantly segregated in the phases.Thus the existence of hydrogen-rich rare earth bearing eompounds is confirmed.It indicates that the rare earths have a hydrogen fixation effect in aluminium and aluminium alloys.
基金supported by the National Natural Science Foundation of China(Grant Nos.51301008 and 51171003)the Beijing Natural Science Foundation,China(Grant No.1112005)
文摘In this paper, we study the effects of Pr substitution on the hydrogenating process and magnetocaloric properties of La（1-x）PrxFe11.4Si1.6Hy hydrides. The powder x-ray diffraction patterns of the La1-xPrxFe11.4Si1.6 and its hydrides show that each of the alloys is crystallized into the single phase of cubic Na Zn13-type structure. There are hydrogen-absorbing plateaus under 0.4938 MPa and 0.4882 MPa in the absorbing curves for the La0.8Pr0.2Fe11.4Si1.6 and La0.6Pr0.4Fe11.4Si1.6 compounds. The releasing processes lag behind the absorbing process, which is obviously different from the coincidence between absorbing and releasing curves of the La Fe11.4Si1.6 compound. The remnant hydrogen content for La0.6Pr0.4Fe11.4Si1.6 is significantly more than that for La0.8Pr0.2Fe11.4Si1.6 after hydrogen desorption, indicating that more substitutions of Pr for La are beneficial to retaining more hydrogen atoms in the alloys. The values of maximum magnetic entropy change are 14.91 J/kg·K and 17.995 J/kg·K for La0.8Pr0.2Fe11.4Si1.6H0.13 and La0.6Pr0.4Fe11.4Si1.6H0.87,respectively.
基金Project supported by the National Natural Science Foundation of China(Grant No.11935004).
文摘The development of reliable fusion energy is one of the most important challenges in this century.The accelerated degradation of structural materials in fusion reactors caused by neutron irradiation would cause severe problems.Due to the lack of suitable fusion neutron testing facilities,we have to rely on ion irradiation experiments to test candidate materials in fusion reactors.Moreover,fusion neutron irradiation effects are accompanied by the simultaneous transmutation production of helium and hydrogen.One important method to study the He-H synergistic effects in materials is multiple simultaneous ion beams(MSIB)irradiation that has been studied for decades.To date,there is no convincing conclusion on these He-H synergistic effects among these experiments.Recently,a multiple ion beam in-situ transmission electron microscopy(TEM)analysis facility was developed in Xiamen University(XIAMEN facility),which is the first triple beam system and the only in-running in-situ irradiation facility with TEM in China.In this work,we conducted the first high-temperature triple simultaneous ion beams irradiation experiment with TEM observation using the XIAMEN facility.The responses to in-situ triple-ion beams irradiation in austenitic steel 304L SS and ferritic/martensitic steel CLF-1 were studied and compared with the results in dual-and single-ion beam(s)irradiated steels.Synergistic effects were observed in MSIB irradiated steels.Helium was found to be critical for cavity formation,while hydrogen has strong synergistic effect on increasing swelling.
基金supported by the major research program from the State Ministry of Science and Technology (No. 2009CB939901)
文摘The geometric and electronic properties of some hydrogenated silicon clusters in the presence of oxygen on the surface have been investigated.The density functional theory with generalized gradient approximation functional was applied in our calculations.By calculating the total energy,the double bond Si=O is shown to be more stable than the bridge bond Si-O-Si for large size oxidized clusters.The results of Mulliken population analysis indicate that a so-called passivation effect is enhanced by oxidization effects.From the energy band structures and density of states,we find that some localized states are induced by the p-orbital of O atom mainly and reduce the energy gaps substantially.
基金supported by the National High Technology Research and Development Program of China(863 Program)(2012AA053305)the International Cooperation Project from Ministry of Science and Technology of China(2010DFA64080)
文摘In this work, the morphologies and pore structures of a series of corncob-derived activated carbons and zeolite templated carbon with ultrahigh surface area were carefully investigated by SEM, HRTEM and N2-sorption characterization technologies. The high-pressure hydrogen uptake performance was analyzed using standard Pressure-Composition-Temperature apparatus in order to study the pore size effects on hydrogen uptake. These as-obtained porous carbons showed different characteristics of pore size distribution as well as specific surface area. The results indicate that the most effective pores for adsorbing hydrogen depended on the storage pressure. These ultramicropores （0.65-0.85 nm） could be the most effective pores on excess H2 uptake at 1 bar, however, micropores （0.85-2 nm） would play a more important role in excess H2 uptake at higher pressure at 77 K. At room temperature, pore size effects on H2 uptake capacity were very weak. Both specific surface area and total pore volume play more important roles than pore size for H2 uptake at room temperature, which was clearly different from that at 77 K. For applications in future, the corncob-derived activated carbons can be more available than zeolite templated carbons at 77 K. Element doping enhanced hydrogen uptake could be main research direction for improving H2 uptake capacity at room temperature.
文摘Time-dependent density functional theory （TDDFT） and femtosecond transient absorption spectroscopy were used to investigate the photophysical properties of 2,3-dihydro-3-keto-lH- pyrido[3,2,1-kl]phenothiazine （PTZ4） and 3-keto-lH-pyrido[3,2,1-kl]phenothiazine （PTZ5）. The calculated results obtained from TDDFT suggest that the red-shifts of the absorption spectra of these two fluorophores in methanol are due to the formation of hydrogen-bonded complexes at the ground state. Four conformers of PTZ4 were obtained by TDDFT. The two fluorescence peaks of PTZ4 in tetrahydrofuran （THF） came from the ICT states of the four conformers. The fluorescence of PTZ4 in THF showed a dependence on the excitation wavelength because of butterfly bending. The excited state dynamics of PTZ4 in THF and methanol were obtained by transient absorption spectroscopy. The lifetime of the excited PTZ4 in methanol was 53.8 ps, and its relaxation from the LE state to the ICT state was completed within several picoseconds. The short lifetime of excited PTZ4 in methanol was due to the formation of out-of-plane model hydrogen bonds between PTZ4 and methanol at the excited state.
基金supported by the Natural Science Foundation of China (91545115,21473145,and 21403178)the Postgraduate Basic Innovative Research Program of Xiamen University (201412G001)the Program for Innovative Research Team in Chinese Universities (no.IRT_14R31)
文摘Cu-x-Fe-y/SiO2 catalysts were prepared using urea-assisted sol-gel method. The structure and physicochemical properties of the catalysts were characterized using N-2 adsorption-desorption, transmission electron microscopy, H-2-temperature-programmed reduction, powder X-ray diffraction, and X-ray photoelectron spectroscopy. Compared with monometallic Cu or Fe catalysts, the bimetallic Cu-x-Fe-y/SiO2 catalysts exhibited enhanced catalytic performance for the selective hydrogenation of diethyl malonate to 1,3-propanediol. The bimetallic catalyst with an optimal Cu/Fe atomic ratio of 2 exhibited the highest activity, which yielded 96.3% conversion to diethyl malonate and 93.3% selectivity to 1,3-propanediol under the optimal reaction conditions. Characterization results revealed that interactions between Cu and Fe contributed to the improvement of diethyl malonate conversion and selectivity to 1,3-propanediol. The X-ray photoelectron spectroscopy results revealed that the addition of appropriate amount of Fe species enhanced the reduction of Cu2+ species, thereby increasing the Cu-0 species on the surface of bimetallic catalyst. It led to a better chemisorption capacity of hydrogen and further promoted of the activation of hydrogen molecule. The ethyl acetate temperature-programmed desorption results indicated that the FeOx species provided the additional adsorption sites for substrate molecules, and they activated the C=O bond. The improved catalytic performance of bimetallic Cu-x-Fe-y/SiO2 catalyst was mainly attributed to the synergistic effect between Cu-0 and FeOx species. (C) 2016 Science Press and Dalian Institute of Chemical Physics, Chinese Academy of Sciences. Published by Elsevier B.V. and Science Press. All rights reserved.
基金Project supported by the National Natural Science Foundation of China(21643008)
文摘Hydrogen purification must be done to meet the different purposes of hydrogen utilization.In the present work,it is confirmed that the catalyst Ni/CeO2 has the highest activity for total methanation(Total MET) of CO and CO2,and is thus most suitable for hydrogen purification for ammonia synthesis.While,the catalyst Ni/ZrO2 appears the best one for selective methanation of CO(CO-SMET) in the H2-rich gas to produce clean fuel for proton exchange membrane fuel cell(PEMFC).In spite of this,the catalyst Ni/ZrO2 without adding chlorine ions as promoter is not yet capable of removing the CO in the reformate gas to below 10 ppm in a wide reaction temperature range by the way of CO-SMET.Adding chlorine ions as promoter is indeed not favorable for practical application due to its gradual loss in the catalytic reaction as proved in our previous work.Therefore,a step to decrease CO2 concentration(called as de-CO2 step) is suggested to be set prior to the CO-SMET step in this work.It is proved that such combination of de-CO2 step and CO-SMET step is efficient to achieve a deep removal of CO to below 10 ppm with a high selectivity more than 50% in a wide reaction temperature range of 220-280℃over the catalyst Ni/ZrO2 without adding chlorine ions as promoter.The combined process has potential for practical application,at least in the large-scale power plant of PEMFC.
文摘The method of numerical simulation is used to fit the relationship between the photoconductivity in films and the illumination time. The generation and process rule of kinds of different charged defect states during illumination are revealed. It is found surprisingly that the initial photoconductivity determines directly the total account of photoconductivity degradation of sample.
文摘Studies of direction of photoisomerization of retinal,retinonitrile,a- retinonitrile and a trienenitrile analog in different solvents with varying wave- lengths of excitation and reaction temperature led to the conclusion that the well known solvent dependent photochemistry of retinoids is due to selective excitation of the hydrogen bonded species.
文摘In this paper, hydrogen is first utilized in the study on methane coupling under nonequilibrium plasma. Results indicate that the addition of hydrogen is beneficial. to the methane coupling so as to increase the conversion rate of methane and the yield of C2 hydrocarbon with a gradual increase in the addition of hydrogen in a certain range of proportionality. This conclusion explores a new route of hydrogenated methane coupling.
基金Supported by the National Natural Science Foundation of China(No. 2 9972 0 38)
文摘B3LYP/6 31+g( d ) calculations were performed on the hydrogen bonded complexes between substituted phenolates and HF, H 2O as well as NH 3. It was found that some properties of the non covalent complexes, including the interaction energies, donor acceptor (host vip) distances, bond lengths, and vibration frequencies, could show well defined substituent effects. Thus, from the substituent studies we can not only understand the mechanism of a particular non covalent interaction better, but also easily predict the interaction energies and structures of a particular non covalent complex, which might otherwise be very hard or resource consuming to be known. This means that substituent effect is indeed a useful tool to be used in supramolecular chemistry and therefore, many valuable studies remain to be carried out.
