Energy supply dominated by fossil energy has been and remains the main cause of carbon dioxide emissions,the major greenhouse gas leading to the current grave climate change challenges.Many technical pathways have bee...Energy supply dominated by fossil energy has been and remains the main cause of carbon dioxide emissions,the major greenhouse gas leading to the current grave climate change challenges.Many technical pathways have been proposed to address the challenges.Carbon capture and utilization(CCU) represents one of the approaches and thermochemical CO_(2) splitting driven by thermal energy is a subset of the CCU,which converts the captured CO_(2) into CO and makes it possible to achieve closed-loop carbon recirculation.Redox-active catalysts are among the most critical components of the thermochemical splitting cycles and perovskites are regarded as the most promising catalysts.Here we review the latest advancements in thermochemical cycles based on perovskites,covering thermodynamic principles,material modifications,reaction kinetics,oxygen pressure control,circular strategies,and demonstrations to provide a comprehensive overview of the topical area.Thermochemical cycles based on such materials require the consideration of trade-off between cost and efficiency,which is related to actual material used,operation mode,oxygen removal,and heat recovery.Lots of efforts have been made towards improving reaction rates,conversion efficiency and cycling stability,materials related research has been lacking-a key aspect affecting the performance across all above aspects.Double perovskites and composite perovskites arise recently as a potentially promising addition to material candidates.For such materials,more effective oxygen removal would be needed to enhance the overall efficiency,for which thermochemical or electrochemical oxygen pumps could contribute to efficient oxygen removal as well as serve as means for inert gas regeneration.The integration of thermochemical CO_(2) splitting process with downstream fuel production and other processes could reduce costs and increase efficiency of the technology.This represents one of the directions for the future research.展开更多
This study aimed to establish a closed-cycle operation technology with high thermal efficiency in the thermochemical sulfur-iodine cycle for large-scale hydrogen production.A series of experimental studies were perfor...This study aimed to establish a closed-cycle operation technology with high thermal efficiency in the thermochemical sulfur-iodine cycle for large-scale hydrogen production.A series of experimental studies were performed to investigate the occurrence of side reactions in both the H2SO4 and HI x phases from the H2SO4/HI/I2/H2O quaternary system within a constant temperature range of 323-363 K.The effects of iodine content,water content and reaction temperature on the side reactions were evaluated.The results showed that an increase in the reaction temperature promoted the side reactions.However,they were prevented as the iodine or water content increased.The occurrence of side reactions was faster in kinetics and more intense in the H2SO4 phase than in the HI x phase.The sulfur or hydrogen sulfide formation reaction or the reverse Bunsen reaction was validated under certain conditions.展开更多
The Bunsen reaction is the center reaction for both the sulfur–iodine water splitting cycle for hydrogen production and the novel hydrogen sulfide splitting cycle for hydrogen and sulfuric acid production from the su...The Bunsen reaction is the center reaction for both the sulfur–iodine water splitting cycle for hydrogen production and the novel hydrogen sulfide splitting cycle for hydrogen and sulfuric acid production from the sulfur-containing gases.This paper reviews the research progress of the Bunsen reaction in recent 10–15 years.Researches were initially focused on the optimization of the operating conditions of the conventional Bunsen reaction requiring excessive water and iodine to improve the products separation efficiency and to avoid the side reactions and iodine vapor deposition.Alternative methods including electrochemical methods,precipitation methods,and non-aqueous solvent methods had their respective advantages,but still faced challenges.In development of the technology of H2S splitting cycle,dissolving iodine in toluene solvent could render the Bunsen reaction to occur with the flowable I2 stream at ambient temperature such that the side reactions and iodine vaporization can be avoided and the corrosion hazard lessened.It also prevented the Bunsen reaction from using excessive iodine and water.The products from the Bunsen reaction including HI,H2SO4,H2O,and toluene could be directly electrolyzed.展开更多
We investigate the evolution of stress fields during the supercontinent cycle using the 2D Cartesian geometry model of thermochemical convection with the non-Newtonian rheology in the presence of floating deformable c...We investigate the evolution of stress fields during the supercontinent cycle using the 2D Cartesian geometry model of thermochemical convection with the non-Newtonian rheology in the presence of floating deformable continents.In the course of the simulation,the supercontinent cycle is implemented several times.The number of continents considered in our model as a function of time oscillates around 3.The lifetime of a supercontinent depends on its dimension.Our results suggest that immediately before a supercontinent breakup,the over-lithostatic horizontal stresses in it(referring to the mean value by the computational area)are tensile and can reach-250 MPa.At the same time,a vast area beneath a supercontinent with an upward flow exhibits clearly the over-lithostatic compressive horizontal stresses of 50-100 МРа.The reason for the difference in stresses in the supercontinent and the underlying mantle is a sharp difference in their viscosity.In large parts of the mantle,the over-lithostatic horizontal stresses are in the range of±25 MPa,while the horizontal stresses along subduction zones and continental margins are significantly larger.During the process of continent-to-continent collisions,the compressive stresses can approximately reach 130 MPa,while within the subcontinental mantle,the tensile over-lithostatic stresses are about-50 MPa.The dynamic topography reflects the main features of the su-percontinent cycle and correlates with real ones.Before the breakup and immediately after the disin-tegration of the supercontinent,continents experience maximum uplift.During the supercontinent cycle,topographic heights of continents typically vary within the interval of about±1.5 km,relatively to a mean value.Topographic maxima of orogenic formations to about 2-4 km are detected along continent-to-continent collisions as well as when adjacent subduction zones interact with continental margins.展开更多
Hydrogen production via a two-step thermochemical cycle based on solar energy has attracted increasing attention.However,the severe irreversible loss causes the low efficiency.To make sense of the irreversibility,an i...Hydrogen production via a two-step thermochemical cycle based on solar energy has attracted increasing attention.However,the severe irreversible loss causes the low efficiency.To make sense of the irreversibility,an in-depth thermodynamic model for the solar driven two-step thermochemical cycles is proposed.Different from previous literatures solely focusing on the energy loss and irreversibility of devices,this work decouples a complex energy conversion process in three sub-processes,i.e.,reaction,heat transfer and re-radiation,acquiring the cause of irreversible loss.The results from the case study indicate that the main irreversibility caused by inert sweeping gas for decreasing the reduction reaction temperature dominates the cycle efficiency.Decreasing reduction reaction temperature without severe energy penalty of inert sweeping gas is important to reducing this irreversible loss.A favorable performance is achieved by decreasing re-oxidation rate,increasing hydrolysis conversion rate and achieving a thermochemical cycle with a lower equilibrium temperature of reduction reaction at atmosphere pressure.The research clarifies the essence of process irrrversibility in solar thermichemical cycles,and the findings point out the potential to develop efficient solar driven two-step thermochemical cycles for hydrogen production.展开更多
Developing an efficient redox material is crucial for thermochemical cycles that produce solar fuels (e.g. H2 and CO), enabling a sustainable energy supply. In this study, zirconia-doped cerium oxide (Ce1-xZrxO2) was ...Developing an efficient redox material is crucial for thermochemical cycles that produce solar fuels (e.g. H2 and CO), enabling a sustainable energy supply. In this study, zirconia-doped cerium oxide (Ce1-xZrxO2) was tested in CO2-splitting cycles for the production of CO. The impact of the Zr-content on the splitting performance was investigated within the range 0 ≤ x < 0.4. The materials were synthesized via a citrate nitrate auto combustion route and subjected to thermogravimetric experiments. The results indicate that there is an optimal zirconium content, x = 0.15, improving the specific CO2-splitting performance by 50% compared to pure ceria. Significantly enhanced performance is observed for 0.15 ≤ x ≤ 0.225. Outside this range, the performance decreases to values of pure ceria. These results agree with theoretical studies attributing the improvements to lattice modification. Introducing Zr4+ into the fluorite structure of ceria compensates for the expansion of the crystal lattice caused by the reduction of Ce4+ to Ce3+. Regarding the reaction conditions, the most efficient composition Ce0.85Zr0.15O2 enhances the required conditions by a temperature of 60 K or one order of magnitude of the partial pressure of oxygen p(O2) compared to pure ceria. The optimal composition was tested in long-term experiments of one hundred cycles, which revealed declining splitting kinetics.展开更多
The objective of this work is to demonstrate the utilization of the power of simulation tools to perform an exergy analysis of a process.Exergy analysis,being a new and useful thermodynamics tool,will be applied to on...The objective of this work is to demonstrate the utilization of the power of simulation tools to perform an exergy analysis of a process.Exergy analysis,being a new and useful thermodynamics tool,will be applied to one of the newest research fields in hydrogen production.One of the many advantages of computer simulation is elimination of the need to construct a pilot plant.Presently,extensive research is underway to come up with the production and use of clean fuels.The research entails performing pilot studies and proof of concept experiments using validated models.The research is further extended to various analyses such as safety,economic sustainability and energy efficiency of the processes involved.The production of hydrogen through thermochemical water splitting processes is one of the newest technologies and is expected to compete with the existing technologies.Among a wide range of thermochemical cycles,the sulfur-iodine(SI)thermochemical cycle process has been proposed as a promising technology for the production of hydrogen.In this research,we demonstrate how a commercial simulator can be used to perform an energy and exergy analysis of the SI water splitting process.Using a commercial simulator,a process flowsheet is developed based on research findings presented by other authors and an energy-exergy analysis is carried out on the process.The method of energy–exergy analysis used in this presentation indicates that an energy and exergy efficiency of 17%and 24%can be attained,respectively,in the conceptual design of the SI cycle.展开更多
Inspired by the promising hydrogen production in the solar thermochemical(STC)cycle based on non-stoichiometric oxides and the operation temperature decreasing effect of methane reduction,a high-fuel-selectivity and C...Inspired by the promising hydrogen production in the solar thermochemical(STC)cycle based on non-stoichiometric oxides and the operation temperature decreasing effect of methane reduction,a high-fuel-selectivity and CH4-introduced solar thermochemical cycle based on MoO2/Mo is studied.By performing HSC simulations,the energy upgradation and energy conversion potential under isothermal and non-isothermal operating conditions are compared.In the reduction step,MoO2:CH4=2 and 1020 K<Tred<1600 K are found to be most favorable for syngas selectivity and methane conversion.Compared to the STC cycle without CH4,the introduction of methane yields a much higher hydrogen production,especially at the lower temperature range and atmospheric pressure.In the oxidation step,a moderately excessive water is beneficial for energy conversion whether in isothermal or non-isothermal operations,especially at H2O:Mo=4.In the whole STC cycle,the maximum non-isothermal and isothermal efficiency can reach 0.417 and 0.391 respectively.In addition,the predicted efficiency of the second cycle is also as high as 0.454 at Tred=1200 K and Toxi=400 K,indicating that MoO2 could be a new and potential candidate for obtaining solar fuel by methane reduction.展开更多
In recent years,oxygen storage materials(OSMs)have been widely used in many fields.It would be particularly important for researchers to design high-oxygen-uptake/release-rate materials.In this study,various synthesis...In recent years,oxygen storage materials(OSMs)have been widely used in many fields.It would be particularly important for researchers to design high-oxygen-uptake/release-rate materials.In this study,various synthesis processes were used to successfully synthesize YBaCo_(4)O_(7+δ)and comprehensively investigate their potential applications.Compa red with traditional solid-state reaction method and co-precipitation method,the results demonstrated that the utilization of mechanical ball milling treatment on co-precipitated precursors could lead to samples with reversible oxygen uptake/release under an oxidative atmosphere at low temperatures.The resultant materials exhibited fast oxygen absorption/desorption rate that could uptake/release oxygen directly to the equilibrium state within 9 min and20 min,respectively.The mechanochemically ball-milled sample possessed outstanding oxygen sto rage performance,which could be attributed to their small particle size,the active outer surface of particles,large specific surface area,and relatively low activation energy.Moreover,the ball-milled sample also exhibited excellent cycling stability during relatively short time spacing.TG results also demonstrated that the ball-milled samples could reversibly uptake/release 2.90 wt.%of excess oxygen(while only 0.70 wt.%for solid-state samples)by adjusting the ambient temperature under pure O_(2) atmosphere,which would make them promising candidates in various applications.This research demonstrated that mechanical treatment could be an effective strategy to tune the properties and oxygen storage capacity(OSC)performances of YBaCo_(4)O_(7+δ).展开更多
文摘Energy supply dominated by fossil energy has been and remains the main cause of carbon dioxide emissions,the major greenhouse gas leading to the current grave climate change challenges.Many technical pathways have been proposed to address the challenges.Carbon capture and utilization(CCU) represents one of the approaches and thermochemical CO_(2) splitting driven by thermal energy is a subset of the CCU,which converts the captured CO_(2) into CO and makes it possible to achieve closed-loop carbon recirculation.Redox-active catalysts are among the most critical components of the thermochemical splitting cycles and perovskites are regarded as the most promising catalysts.Here we review the latest advancements in thermochemical cycles based on perovskites,covering thermodynamic principles,material modifications,reaction kinetics,oxygen pressure control,circular strategies,and demonstrations to provide a comprehensive overview of the topical area.Thermochemical cycles based on such materials require the consideration of trade-off between cost and efficiency,which is related to actual material used,operation mode,oxygen removal,and heat recovery.Lots of efforts have been made towards improving reaction rates,conversion efficiency and cycling stability,materials related research has been lacking-a key aspect affecting the performance across all above aspects.Double perovskites and composite perovskites arise recently as a potentially promising addition to material candidates.For such materials,more effective oxygen removal would be needed to enhance the overall efficiency,for which thermochemical or electrochemical oxygen pumps could contribute to efficient oxygen removal as well as serve as means for inert gas regeneration.The integration of thermochemical CO_(2) splitting process with downstream fuel production and other processes could reduce costs and increase efficiency of the technology.This represents one of the directions for the future research.
基金Project (No. 51006088) supported by the National Natural Science Foundation of China
文摘This study aimed to establish a closed-cycle operation technology with high thermal efficiency in the thermochemical sulfur-iodine cycle for large-scale hydrogen production.A series of experimental studies were performed to investigate the occurrence of side reactions in both the H2SO4 and HI x phases from the H2SO4/HI/I2/H2O quaternary system within a constant temperature range of 323-363 K.The effects of iodine content,water content and reaction temperature on the side reactions were evaluated.The results showed that an increase in the reaction temperature promoted the side reactions.However,they were prevented as the iodine or water content increased.The occurrence of side reactions was faster in kinetics and more intense in the H2SO4 phase than in the HI x phase.The sulfur or hydrogen sulfide formation reaction or the reverse Bunsen reaction was validated under certain conditions.
基金financial supports from the National Natural Science Foundation of China(21576183)Natural Science and Technology Research Council of Canada(STPGP-350428-07)
文摘The Bunsen reaction is the center reaction for both the sulfur–iodine water splitting cycle for hydrogen production and the novel hydrogen sulfide splitting cycle for hydrogen and sulfuric acid production from the sulfur-containing gases.This paper reviews the research progress of the Bunsen reaction in recent 10–15 years.Researches were initially focused on the optimization of the operating conditions of the conventional Bunsen reaction requiring excessive water and iodine to improve the products separation efficiency and to avoid the side reactions and iodine vapor deposition.Alternative methods including electrochemical methods,precipitation methods,and non-aqueous solvent methods had their respective advantages,but still faced challenges.In development of the technology of H2S splitting cycle,dissolving iodine in toluene solvent could render the Bunsen reaction to occur with the flowable I2 stream at ambient temperature such that the side reactions and iodine vaporization can be avoided and the corrosion hazard lessened.It also prevented the Bunsen reaction from using excessive iodine and water.The products from the Bunsen reaction including HI,H2SO4,H2O,and toluene could be directly electrolyzed.
文摘We investigate the evolution of stress fields during the supercontinent cycle using the 2D Cartesian geometry model of thermochemical convection with the non-Newtonian rheology in the presence of floating deformable continents.In the course of the simulation,the supercontinent cycle is implemented several times.The number of continents considered in our model as a function of time oscillates around 3.The lifetime of a supercontinent depends on its dimension.Our results suggest that immediately before a supercontinent breakup,the over-lithostatic horizontal stresses in it(referring to the mean value by the computational area)are tensile and can reach-250 MPa.At the same time,a vast area beneath a supercontinent with an upward flow exhibits clearly the over-lithostatic compressive horizontal stresses of 50-100 МРа.The reason for the difference in stresses in the supercontinent and the underlying mantle is a sharp difference in their viscosity.In large parts of the mantle,the over-lithostatic horizontal stresses are in the range of±25 MPa,while the horizontal stresses along subduction zones and continental margins are significantly larger.During the process of continent-to-continent collisions,the compressive stresses can approximately reach 130 MPa,while within the subcontinental mantle,the tensile over-lithostatic stresses are about-50 MPa.The dynamic topography reflects the main features of the su-percontinent cycle and correlates with real ones.Before the breakup and immediately after the disin-tegration of the supercontinent,continents experience maximum uplift.During the supercontinent cycle,topographic heights of continents typically vary within the interval of about±1.5 km,relatively to a mean value.Topographic maxima of orogenic formations to about 2-4 km are detected along continent-to-continent collisions as well as when adjacent subduction zones interact with continental margins.
基金the financial support provided by the National Natural Science Foundation of China(No.52090061)the Basic Science Center Program for Ordered Energy Conversion of the National Natural Science Foundation of China(No.51888103)。
文摘Hydrogen production via a two-step thermochemical cycle based on solar energy has attracted increasing attention.However,the severe irreversible loss causes the low efficiency.To make sense of the irreversibility,an in-depth thermodynamic model for the solar driven two-step thermochemical cycles is proposed.Different from previous literatures solely focusing on the energy loss and irreversibility of devices,this work decouples a complex energy conversion process in three sub-processes,i.e.,reaction,heat transfer and re-radiation,acquiring the cause of irreversible loss.The results from the case study indicate that the main irreversibility caused by inert sweeping gas for decreasing the reduction reaction temperature dominates the cycle efficiency.Decreasing reduction reaction temperature without severe energy penalty of inert sweeping gas is important to reducing this irreversible loss.A favorable performance is achieved by decreasing re-oxidation rate,increasing hydrolysis conversion rate and achieving a thermochemical cycle with a lower equilibrium temperature of reduction reaction at atmosphere pressure.The research clarifies the essence of process irrrversibility in solar thermichemical cycles,and the findings point out the potential to develop efficient solar driven two-step thermochemical cycles for hydrogen production.
基金Part of the work was co-funded by the Initiative and Networking Fund of the Helmholtz Association of German Research Centers.
文摘Developing an efficient redox material is crucial for thermochemical cycles that produce solar fuels (e.g. H2 and CO), enabling a sustainable energy supply. In this study, zirconia-doped cerium oxide (Ce1-xZrxO2) was tested in CO2-splitting cycles for the production of CO. The impact of the Zr-content on the splitting performance was investigated within the range 0 ≤ x < 0.4. The materials were synthesized via a citrate nitrate auto combustion route and subjected to thermogravimetric experiments. The results indicate that there is an optimal zirconium content, x = 0.15, improving the specific CO2-splitting performance by 50% compared to pure ceria. Significantly enhanced performance is observed for 0.15 ≤ x ≤ 0.225. Outside this range, the performance decreases to values of pure ceria. These results agree with theoretical studies attributing the improvements to lattice modification. Introducing Zr4+ into the fluorite structure of ceria compensates for the expansion of the crystal lattice caused by the reduction of Ce4+ to Ce3+. Regarding the reaction conditions, the most efficient composition Ce0.85Zr0.15O2 enhances the required conditions by a temperature of 60 K or one order of magnitude of the partial pressure of oxygen p(O2) compared to pure ceria. The optimal composition was tested in long-term experiments of one hundred cycles, which revealed declining splitting kinetics.
文摘The objective of this work is to demonstrate the utilization of the power of simulation tools to perform an exergy analysis of a process.Exergy analysis,being a new and useful thermodynamics tool,will be applied to one of the newest research fields in hydrogen production.One of the many advantages of computer simulation is elimination of the need to construct a pilot plant.Presently,extensive research is underway to come up with the production and use of clean fuels.The research entails performing pilot studies and proof of concept experiments using validated models.The research is further extended to various analyses such as safety,economic sustainability and energy efficiency of the processes involved.The production of hydrogen through thermochemical water splitting processes is one of the newest technologies and is expected to compete with the existing technologies.Among a wide range of thermochemical cycles,the sulfur-iodine(SI)thermochemical cycle process has been proposed as a promising technology for the production of hydrogen.In this research,we demonstrate how a commercial simulator can be used to perform an energy and exergy analysis of the SI water splitting process.Using a commercial simulator,a process flowsheet is developed based on research findings presented by other authors and an energy-exergy analysis is carried out on the process.The method of energy–exergy analysis used in this presentation indicates that an energy and exergy efficiency of 17%and 24%can be attained,respectively,in the conceptual design of the SI cycle.
基金supported by the Innovation Practice Training Program of College Students,Chinese Academy of Sciences(Application No.20184000028)the Practical Training Program of Beijing University of Higher Education High-level Talents Cross-cultivation(No.16053225)the National Natural Science Foundation of China(Grant Nos.51476163,51806209 and 81801768).
文摘Inspired by the promising hydrogen production in the solar thermochemical(STC)cycle based on non-stoichiometric oxides and the operation temperature decreasing effect of methane reduction,a high-fuel-selectivity and CH4-introduced solar thermochemical cycle based on MoO2/Mo is studied.By performing HSC simulations,the energy upgradation and energy conversion potential under isothermal and non-isothermal operating conditions are compared.In the reduction step,MoO2:CH4=2 and 1020 K<Tred<1600 K are found to be most favorable for syngas selectivity and methane conversion.Compared to the STC cycle without CH4,the introduction of methane yields a much higher hydrogen production,especially at the lower temperature range and atmospheric pressure.In the oxidation step,a moderately excessive water is beneficial for energy conversion whether in isothermal or non-isothermal operations,especially at H2O:Mo=4.In the whole STC cycle,the maximum non-isothermal and isothermal efficiency can reach 0.417 and 0.391 respectively.In addition,the predicted efficiency of the second cycle is also as high as 0.454 at Tred=1200 K and Toxi=400 K,indicating that MoO2 could be a new and potential candidate for obtaining solar fuel by methane reduction.
基金supported by Council for Science, Technology and Innovation (CSTI), Cross-ministerial Strategic Innovation Promotion Program (SIP), “Energy systems toward a decarbonized society” (Funding agency: JST)supported by the JSPS Grant-in-Aid for Scientific Research on Innovative Areas “Mixed anion” (No. 16H06439, 17H05490)+2 种基金Grant-in-Aid for Scientific Research (20H00297)Dynamic Alliance for Open In-novation Bridging Human, Environment and Materials in Network Joint Research Center for Materials and DevicesChina Scholarship Council for providing the scholarship。
文摘In recent years,oxygen storage materials(OSMs)have been widely used in many fields.It would be particularly important for researchers to design high-oxygen-uptake/release-rate materials.In this study,various synthesis processes were used to successfully synthesize YBaCo_(4)O_(7+δ)and comprehensively investigate their potential applications.Compa red with traditional solid-state reaction method and co-precipitation method,the results demonstrated that the utilization of mechanical ball milling treatment on co-precipitated precursors could lead to samples with reversible oxygen uptake/release under an oxidative atmosphere at low temperatures.The resultant materials exhibited fast oxygen absorption/desorption rate that could uptake/release oxygen directly to the equilibrium state within 9 min and20 min,respectively.The mechanochemically ball-milled sample possessed outstanding oxygen sto rage performance,which could be attributed to their small particle size,the active outer surface of particles,large specific surface area,and relatively low activation energy.Moreover,the ball-milled sample also exhibited excellent cycling stability during relatively short time spacing.TG results also demonstrated that the ball-milled samples could reversibly uptake/release 2.90 wt.%of excess oxygen(while only 0.70 wt.%for solid-state samples)by adjusting the ambient temperature under pure O_(2) atmosphere,which would make them promising candidates in various applications.This research demonstrated that mechanical treatment could be an effective strategy to tune the properties and oxygen storage capacity(OSC)performances of YBaCo_(4)O_(7+δ).