The corrosions resulting from defects in painting layers frequently occur in Al alloys, so the application of corrosion preventing systems is also very important. Optimum conditions in terms of electrochemistry in rel...The corrosions resulting from defects in painting layers frequently occur in Al alloys, so the application of corrosion preventing systems is also very important. Optimum conditions in terms of electrochemistry in relation to solution treatment, quenching and artificial aging treatment were established in order to optimize precipitation strengthening conditions intended to enhance the strength of Al alloys. Slow strain rate tests (SSRT) at various applied potentials were conducted in potential range from -1.8 to 0.5 V. The results show that the maximum tensile strengths, elongations and time-to-fracture are shown to be high values. After precipitation strengthening heat treatment, a tendency appear that time-to-fracture increases as elongation increases. In the potential range from -1.3 V to -0.7 V, the specimens show excellent mechanical properties, and thus this range is considered to be a corrosion prevention range.展开更多
Thermodynamic analyses in the literature have shown that solid oxide fuel cells(SOFCs) with proton conducting electrolyte(H-SOFC) exhibited higher performance than SOFC with oxygen ion conducting electrolyte(O-SOFC).H...Thermodynamic analyses in the literature have shown that solid oxide fuel cells(SOFCs) with proton conducting electrolyte(H-SOFC) exhibited higher performance than SOFC with oxygen ion conducting electrolyte(O-SOFC).However, these studies only consider H2 electrochemical oxidation and totally neglect the contribution of CO electrochemical oxidation in O-SOFC. In this short communication, a thermodynamic model is developed to compare the theoretically maximum efficiencies of H-SOFC and O-SOFC, considering the electrochemical oxidation of CO in O-SOFC anode. It is found that O-SOFC exhibits a higher maximum efficiency than H-SOFC due to the contribution from CO electrochemical oxidation, which is contrary to the common understanding of electrolyte effect on SOFC performance. The effects of operating temperature and fuel utilization factor on the theoretical efficiency of SOFC are also analyzed and discussed.展开更多
We study the effect of potential and thermal gradient induced non-equilibrium magnetization in quasi1-d itinerant magnets.A semi-phenomenological theory is employed in conjunction with the drift-diffusion model forthi...We study the effect of potential and thermal gradient induced non-equilibrium magnetization in quasi1-d itinerant magnets.A semi-phenomenological theory is employed in conjunction with the drift-diffusion model forthis study.Using the methods of non-equilibrium thermodynamics,we derive the transport currents correspondingto charge,heat,and magnetization flows in the presence of non-equilibrium magnetization textures.It is shown howtime-dependent magnetic textures give rise to charge and thermal currents even in the absence of external potential andthermal gradients through spin pumping.The presence of dynamical textures also affect the thermodynamic parametersof the system.As an application,we consider the case of a helimagnet.展开更多
It is undisputed that hydrogen will play a great role in our future energetic mix, because it enables the storage of renewable electricity(power-to-H2) and the reversible conversion into electricity in fuel cell, not ...It is undisputed that hydrogen will play a great role in our future energetic mix, because it enables the storage of renewable electricity(power-to-H2) and the reversible conversion into electricity in fuel cell, not to speak of its wide use in the(petro)chemical industry. Whereas in these applications, pure hydrogen is required, today’s hydrogen production is still largely based on fossil fuels and can therefore not be considered pure. Therefore, purification of hydrogen is mandatory, at a large scale. In addition, hydrogen being the lightest gas, its volumetric energy content is well-below its competing fuels, unless it is compressed at high pressures(typically 70 MPa), making compression unavoidable as well. This contribution will detail the means available today for both purification and for compression of hydrogen. It will show that among the available technologies, the electrochemical hydrogen compressor(EHC), which also enables hydrogen purification, has numerous advantages compared to the classical technologies currently used at the industrial scale. EHC has their thermodynamic and operational advantages, but also their ease of use. However, the deployment of EHCs will be viable only if they reach sufficient performances, which implies some specifications that their base materials should stick to. The present contribution will detail these specifications.展开更多
A new electrical method of conductive carbon-film(with waterproof and anticorrosion ability)was proposed to continuously measure crack propagation rate of brittle rock under THMC coupling condition.A self-designed cou...A new electrical method of conductive carbon-film(with waterproof and anticorrosion ability)was proposed to continuously measure crack propagation rate of brittle rock under THMC coupling condition.A self-designed coupling testing system was used to conduct THMC coupling fracture tests of the pre-cracked red sandstone specimens(where the temperature is only changed)by this new electrical method of conductive carbon-film.Calculation results obtained by the energy method coincide well with the test results.And the higher the temperature is,the earlier the crack is initiated and the larger the crack propagation rate and accelerated velocity are,which can prove the validity of the new electrical method.This new electrical method has advantages of continuously measuring crack propagation rate over the conventional electrical,optical and acoustic methods,and can provide important basis for safety assessment and cracking-arrest design of deep rock mass engineering.展开更多
Broadly,the oxygen evolution reaction(OER)has been deeply understood as a significant part of energy conversion and storage.Nevertheless,the anions in the OER catalysts have been neglected for various reasons such as ...Broadly,the oxygen evolution reaction(OER)has been deeply understood as a significant part of energy conversion and storage.Nevertheless,the anions in the OER catalysts have been neglected for various reasons such as inactive sites,dissolution,and oxidation,amongst others.Herein,we applied a model catalyst s-Ni(OH)2 to track the anionic behavior in the catalyst during the electrochemical process to fill this gap.The advanced operando synchrotron radiation Fourier transform infrared(SR-FTIR)spectroscopy,synchrotron radiation photoelectron spectroscopy(SRPES)depth detection and differential X-ray absorption fine structure(D-XAFS)spectrum jointly point out that some oxidized sulfur species(SO_(4)^(2-))will selfoptimize new Ni–S bonds during OER process.Such amazing anionic self-optimization(ASO)behavior has never been observed in the OER process.Subsequently,the optimization-derived component shows a significantly improved electrocatalytic performance(activity,stability,etc.)compared to reference catalyst Ni(OH)_(2).Theoretical calculation further suggests that the ASO process indeed derives a thermodynamically stable structure of the OER catalyst,and then gives its superb catalytic performance by optimizing the thermodynamic and kinetic processes in the OER,respectively.This work demonstrates the vital role of anions in the electrochemical process,which will open up new perspectives for understanding OER and provide some new ideas in related fields(especially catalysis and chemistry).展开更多
The electromotive force (e.m.f.) of solid oxide fuel cells using biomass produced gas (BPG) as the fuels is calculated at 700-1,200 K using an in-house computer program, based on thermodynamic equilibrium analysis...The electromotive force (e.m.f.) of solid oxide fuel cells using biomass produced gas (BPG) as the fuels is calculated at 700-1,200 K using an in-house computer program, based on thermodynamic equilibrium analysis. Tour program also predicts the concentration of oxygen in the fuel chamber as well as the concentration of equilibrium species such as H2, CO, CO2 and CH4. Compared with using hydrogen as a fuel, the e.m.f. for cells using BPG as the fuels is relative low and strongly influenced by carbon deposition. To remove carbon deposition, the optimum amount of H2O to add is determined at various operating temperatures. Further the e.m.f, for cells based on yttria stabilized zirconia and doped ceria as electrolytes are compared. The study reveals that when using BPG as fuel, the depression of e.m.f, for a SOFC using doped ceria as electrolyte is relatively small when compared with that using Yttria stabilized zirconia.展开更多
Exploring the production and application of clean energy has always been the core of sustainable development.As a clean and sustainable technology,electrocatalysis has been receiving widespread attention.It is crucial...Exploring the production and application of clean energy has always been the core of sustainable development.As a clean and sustainable technology,electrocatalysis has been receiving widespread attention.It is crucial to achieve efficient,stable and cheap electrocatalysts.However,the traditional“trial and error”method is time-consuming,laborious and costly.In recent years,with the significant increase in computing power,computations have played an important role in electrocatalyst design.Nevertheless,it is still difficult to search for advanced electrocatalysts in the vast chemical space through traditional density functional theory(DFT)computations.Fortunately,the development of machine learning and interdisciplinary integration will inject new impetus into targeted design of electrocatalysts.Machine learning is able to predict electrochemical performances with an accuracy close to DFT.Here we provide an overview of the application of machine learning in electrocatalyst design,including the prediction of structure,thermodynamic properties and kinetic barriers.We also discuss the potential of explicit solvent model combined with machine learning molecular dynamics in this field.Finally,the favorable circumstances and challenges are outlined for the future development of machine learning in electrocatalysis.The studies on electrochemical processes by machine learning will further realize targeted design of high-efficiency electrocatalysts.展开更多
Water-soluble gelatin-PbS bionanocomposites (BNCs) were synthesized via a facile one-pot chemical reaction method at pH 7.40. The samples were characterized by transmission electron microscopy (TEM), X-ray diffrac...Water-soluble gelatin-PbS bionanocomposites (BNCs) were synthesized via a facile one-pot chemical reaction method at pH 7.40. The samples were characterized by transmission electron microscopy (TEM), X-ray diffraction (XRD), UV-vis absorption spectra (UV-vis), Fourier transform infrared spectra (FT-IR) and circular dichroism (CD). FT-IR data were used to envis- age the binding of PbS particles with oxygen atoms of carbonyl groups of gelatin molecule. The possible integration mechanism between gelatin and PbS was discussed in detail. The effect of Pb2+ and PbS on the conformations of gelatin has also been analyzed by means of UV-vis, CD and FT-IR spectra, resulting in less c^-helix content and more open structures ([3-sheet, r-turn, or expanded). A new formula to calculate the association constant was proposed according to the relationship between the absorbance of gelatin-PbS BNCs and the free concentration of PbS, and apparent association constants K (298/303/308 K: 3.11/2.00/1.60 × 10^6 tool/L) at three different temperatures were calculated based on this formula. Thermodynamic parameters such as AG^θ, △Hθ and △S^θ were also determined. The results of the thermodynamic investigations indicated that the reaction was spontaneous (AG^θ 〈 0), and enthalpy-driven (△H^8 〈 0).展开更多
Sodium layered oxides generally suffer from deep-desodiation instability in P2 structure and sluggish kinetics in O3 structure.It will be great to design P2/O3 biphasic materials that bring the complementary merits of...Sodium layered oxides generally suffer from deep-desodiation instability in P2 structure and sluggish kinetics in O3 structure.It will be great to design P2/O3 biphasic materials that bring the complementary merits of both structures.However,such exploration is hindered by the ambiguous mechanism of material formation.Herein,supported by theoretical simulations and various spectroscopies,we prove that P2/O3 biphasic structures essentially originate from the internal heterogeneity of cationic potential,which can be realized by constraining the temperature-driven ion diffusion during solid-state reactions.Consequently,P2/O3 biphasic Na_(0.7)Ni_(0.2)Cu_(0.1)Fe_(0.2)Mn_(0.5)O_(2)-δ with well-designed quaternary composition is successfully obtained,exhibiting much-improved rate capabilities(62 mAh g^(-1)at 2.4 A g^(-1)) and cycling stabilities(84%capacity retention after 500 cycles)than its single-phase analogues.Furthermore,synchrotron-based diffraction and X-ray absorption spectroscopy are employed to unravel the underlying sodium-storage mechanism of the P2/O3 biphasic structure.This work presents new insights toward the rational design of advanced layered cathodes for sodium-ion batteries.展开更多
Coal is still a major source of energy, also a major source of SO_2, NOx and CO_2 emission though. Removal of SO_2 and NOx doubled the cost of power generation, and capture of CO_2 is equivalent to double the market p...Coal is still a major source of energy, also a major source of SO_2, NOx and CO_2 emission though. Removal of SO_2 and NOx doubled the cost of power generation, and capture of CO_2 is equivalent to double the market price of power coal. The GCP (green coal power) is the power generated in coal-combustion with zero emission. The author indicates that it is possible to make coal-fired power plants emission free based on thermodynamic analysis and purposely designed experiments using SFG (simulated flue gases). It is concluded in the study that all SO_2 and NOx in the post-combustion flue gas are reduced to inoffensive substances at temperature lower than 750 ℃ when contacting carbon and elemental sulfur is separated in succeeded cooling of flue gas at temperatures 200-400 ℃, and the ultrafine dusts are trapped in condensed water at temperature blow 100 ℃. Based on chemical engineering expertise the author is sure that the cost for removing acid gases is much lower than any clean coal technologies known to today. Instead of capture, the remained CO_2 is converted to CO in the second time contact with carbon at 900-950 ℃. CO is the raw material of chemical synthesis and, thus, CO_2 is stored in chemical products such as methanol, fertilizer, plastics, etc. The simple and low-cost processing allows GCP utilized in practice easily.展开更多
Steady-state model of a high-temperature solid oxide fuel cell (SOFC) is considered, which refers to constant chemical potentials of incoming hydrogen fuel and oxidant. Lowering of the cell voltage below its reversi...Steady-state model of a high-temperature solid oxide fuel cell (SOFC) is considered, which refers to constant chemical potentials of incoming hydrogen fuel and oxidant. Lowering of the cell voltage below its reversible value is attributed to polarizations and imperfect conversions of reactions. An imperfect power formula summarizes the effect of transport laws, irreversible polarizations and efficiency of power yield. Reversible electrochemical theory is extended to the case with dissipative chemical reactions; this case includes systems with incomplete conversions, characterized by "reduced affinities" and an idle run voltage. Efficiency drop is linked with thermodynamic and electrochemical irreversibilities expressed in terms of polarizations (activation, concentration and ohmic). Effect of incomplete conversions is modeled by assuming that substrates can be remained after the reaction and that side reactions may occur. Optimum and feasibility conditions are discussed for basic input parameters of the cell. Calculations of maximum power show that the data differ for power generated and consumed and depend on current intensity, number of mass transfer units, polarizations, electrode surface area, average chemical rate, etc.. These data provide bounds for SOFC energy generators, which are more exact and informative than reversible bounds for electrochemical transformation.展开更多
Based on thermodynamics and physical chemistry theory,the theoretical energy consumption (TEC) of the typical separating processes of Al,Ca and Mg has been calculated and analyzed.This paper attempts to prove that the...Based on thermodynamics and physical chemistry theory,the theoretical energy consumption (TEC) of the typical separating processes of Al,Ca and Mg has been calculated and analyzed.This paper attempts to prove that the thermal method is more reasonable than the electrolytic methods to separate Al,Ca and Mg under the domestic circumstances of the low efficiency of coal-firing power plant at present.展开更多
文摘The corrosions resulting from defects in painting layers frequently occur in Al alloys, so the application of corrosion preventing systems is also very important. Optimum conditions in terms of electrochemistry in relation to solution treatment, quenching and artificial aging treatment were established in order to optimize precipitation strengthening conditions intended to enhance the strength of Al alloys. Slow strain rate tests (SSRT) at various applied potentials were conducted in potential range from -1.8 to 0.5 V. The results show that the maximum tensile strengths, elongations and time-to-fracture are shown to be high values. After precipitation strengthening heat treatment, a tendency appear that time-to-fracture increases as elongation increases. In the potential range from -1.3 V to -0.7 V, the specimens show excellent mechanical properties, and thus this range is considered to be a corrosion prevention range.
基金Supported by Hong Kong Research Grant Council(PolyU 5238/11E)
文摘Thermodynamic analyses in the literature have shown that solid oxide fuel cells(SOFCs) with proton conducting electrolyte(H-SOFC) exhibited higher performance than SOFC with oxygen ion conducting electrolyte(O-SOFC).However, these studies only consider H2 electrochemical oxidation and totally neglect the contribution of CO electrochemical oxidation in O-SOFC. In this short communication, a thermodynamic model is developed to compare the theoretically maximum efficiencies of H-SOFC and O-SOFC, considering the electrochemical oxidation of CO in O-SOFC anode. It is found that O-SOFC exhibits a higher maximum efficiency than H-SOFC due to the contribution from CO electrochemical oxidation, which is contrary to the common understanding of electrolyte effect on SOFC performance. The effects of operating temperature and fuel utilization factor on the theoretical efficiency of SOFC are also analyzed and discussed.
文摘We study the effect of potential and thermal gradient induced non-equilibrium magnetization in quasi1-d itinerant magnets.A semi-phenomenological theory is employed in conjunction with the drift-diffusion model forthis study.Using the methods of non-equilibrium thermodynamics,we derive the transport currents correspondingto charge,heat,and magnetization flows in the presence of non-equilibrium magnetization textures.It is shown howtime-dependent magnetic textures give rise to charge and thermal currents even in the absence of external potential andthermal gradients through spin pumping.The presence of dynamical textures also affect the thermodynamic parametersof the system.As an application,we consider the case of a helimagnet.
基金The authors thank the Auvergne Rhone-Alpes region for the funding of the PhD thesis of Marine TregaroPart of the work has been performed within the framework of the Centre of Excellence of Multifunctional Architectured Materials“CEMAM”no.ANR-10-LABX-44-01Both MR and MT make their PhD in the frame of the Eco-Sesa project,funded by IDEX Universite Grenoble Alpes.
文摘It is undisputed that hydrogen will play a great role in our future energetic mix, because it enables the storage of renewable electricity(power-to-H2) and the reversible conversion into electricity in fuel cell, not to speak of its wide use in the(petro)chemical industry. Whereas in these applications, pure hydrogen is required, today’s hydrogen production is still largely based on fossil fuels and can therefore not be considered pure. Therefore, purification of hydrogen is mandatory, at a large scale. In addition, hydrogen being the lightest gas, its volumetric energy content is well-below its competing fuels, unless it is compressed at high pressures(typically 70 MPa), making compression unavoidable as well. This contribution will detail the means available today for both purification and for compression of hydrogen. It will show that among the available technologies, the electrochemical hydrogen compressor(EHC), which also enables hydrogen purification, has numerous advantages compared to the classical technologies currently used at the industrial scale. EHC has their thermodynamic and operational advantages, but also their ease of use. However, the deployment of EHCs will be viable only if they reach sufficient performances, which implies some specifications that their base materials should stick to. The present contribution will detail these specifications.
基金Projects(51474251,51874351) supported by the National Natural Science Foundation of China
文摘A new electrical method of conductive carbon-film(with waterproof and anticorrosion ability)was proposed to continuously measure crack propagation rate of brittle rock under THMC coupling condition.A self-designed coupling testing system was used to conduct THMC coupling fracture tests of the pre-cracked red sandstone specimens(where the temperature is only changed)by this new electrical method of conductive carbon-film.Calculation results obtained by the energy method coincide well with the test results.And the higher the temperature is,the earlier the crack is initiated and the larger the crack propagation rate and accelerated velocity are,which can prove the validity of the new electrical method.This new electrical method has advantages of continuously measuring crack propagation rate over the conventional electrical,optical and acoustic methods,and can provide important basis for safety assessment and cracking-arrest design of deep rock mass engineering.
基金supported in part by the National Key R&D Program of China(2017YFA0303500)the National Natural Science Foundation of China(U1932201,21727801,and 51902303)+4 种基金the National Natural Science Foundation of China-Ministry of Foreign Affairs and International Cooperation of Italy(51861135202)CAS International Partnership Program(211134KYSB20190063)Key Research Program of Frontier Sciences(QYZDB-SSW-SLH018)the University of Science and Technology of China start-up fundCAS Interdisciplinary Innovation Team。
文摘Broadly,the oxygen evolution reaction(OER)has been deeply understood as a significant part of energy conversion and storage.Nevertheless,the anions in the OER catalysts have been neglected for various reasons such as inactive sites,dissolution,and oxidation,amongst others.Herein,we applied a model catalyst s-Ni(OH)2 to track the anionic behavior in the catalyst during the electrochemical process to fill this gap.The advanced operando synchrotron radiation Fourier transform infrared(SR-FTIR)spectroscopy,synchrotron radiation photoelectron spectroscopy(SRPES)depth detection and differential X-ray absorption fine structure(D-XAFS)spectrum jointly point out that some oxidized sulfur species(SO_(4)^(2-))will selfoptimize new Ni–S bonds during OER process.Such amazing anionic self-optimization(ASO)behavior has never been observed in the OER process.Subsequently,the optimization-derived component shows a significantly improved electrocatalytic performance(activity,stability,etc.)compared to reference catalyst Ni(OH)_(2).Theoretical calculation further suggests that the ASO process indeed derives a thermodynamically stable structure of the OER catalyst,and then gives its superb catalytic performance by optimizing the thermodynamic and kinetic processes in the OER,respectively.This work demonstrates the vital role of anions in the electrochemical process,which will open up new perspectives for understanding OER and provide some new ideas in related fields(especially catalysis and chemistry).
基金V. ACKN0WLEDGMENT This work was supported by the National Natural Science Foundation of China (No.50372066 and No.50332040).
文摘The electromotive force (e.m.f.) of solid oxide fuel cells using biomass produced gas (BPG) as the fuels is calculated at 700-1,200 K using an in-house computer program, based on thermodynamic equilibrium analysis. Tour program also predicts the concentration of oxygen in the fuel chamber as well as the concentration of equilibrium species such as H2, CO, CO2 and CH4. Compared with using hydrogen as a fuel, the e.m.f. for cells using BPG as the fuels is relative low and strongly influenced by carbon deposition. To remove carbon deposition, the optimum amount of H2O to add is determined at various operating temperatures. Further the e.m.f, for cells based on yttria stabilized zirconia and doped ceria as electrolytes are compared. The study reveals that when using BPG as fuel, the depression of e.m.f, for a SOFC using doped ceria as electrolyte is relatively small when compared with that using Yttria stabilized zirconia.
文摘Exploring the production and application of clean energy has always been the core of sustainable development.As a clean and sustainable technology,electrocatalysis has been receiving widespread attention.It is crucial to achieve efficient,stable and cheap electrocatalysts.However,the traditional“trial and error”method is time-consuming,laborious and costly.In recent years,with the significant increase in computing power,computations have played an important role in electrocatalyst design.Nevertheless,it is still difficult to search for advanced electrocatalysts in the vast chemical space through traditional density functional theory(DFT)computations.Fortunately,the development of machine learning and interdisciplinary integration will inject new impetus into targeted design of electrocatalysts.Machine learning is able to predict electrochemical performances with an accuracy close to DFT.Here we provide an overview of the application of machine learning in electrocatalyst design,including the prediction of structure,thermodynamic properties and kinetic barriers.We also discuss the potential of explicit solvent model combined with machine learning molecular dynamics in this field.Finally,the favorable circumstances and challenges are outlined for the future development of machine learning in electrocatalysis.The studies on electrochemical processes by machine learning will further realize targeted design of high-efficiency electrocatalysts.
基金supported by the National Natural Science Foundation of China(21067001)Natural Science Foundation of Guangxi Province(0991083)Innovation Project of Guangxi University for Nationalities(gxun-chx2012091)
文摘Water-soluble gelatin-PbS bionanocomposites (BNCs) were synthesized via a facile one-pot chemical reaction method at pH 7.40. The samples were characterized by transmission electron microscopy (TEM), X-ray diffraction (XRD), UV-vis absorption spectra (UV-vis), Fourier transform infrared spectra (FT-IR) and circular dichroism (CD). FT-IR data were used to envis- age the binding of PbS particles with oxygen atoms of carbonyl groups of gelatin molecule. The possible integration mechanism between gelatin and PbS was discussed in detail. The effect of Pb2+ and PbS on the conformations of gelatin has also been analyzed by means of UV-vis, CD and FT-IR spectra, resulting in less c^-helix content and more open structures ([3-sheet, r-turn, or expanded). A new formula to calculate the association constant was proposed according to the relationship between the absorbance of gelatin-PbS BNCs and the free concentration of PbS, and apparent association constants K (298/303/308 K: 3.11/2.00/1.60 × 10^6 tool/L) at three different temperatures were calculated based on this formula. Thermodynamic parameters such as AG^θ, △Hθ and △S^θ were also determined. The results of the thermodynamic investigations indicated that the reaction was spontaneous (AG^θ 〈 0), and enthalpy-driven (△H^8 〈 0).
基金supported by the National Natural Science Foundation of China(U21A20284)Science and Technology Foundation of Guizhou Province(QKHZC20202Y037)+4 种基金the Science and Technology Innovation Program of Hunan Province(2020RC40052019RS1004)Innovation Mover Program of Central South University(2020CX007)National Research Foundation of Korea(NRF-2017R1A2B3004383)the China Scholarship Council(CSC)for the financial support(202006370306)。
文摘Sodium layered oxides generally suffer from deep-desodiation instability in P2 structure and sluggish kinetics in O3 structure.It will be great to design P2/O3 biphasic materials that bring the complementary merits of both structures.However,such exploration is hindered by the ambiguous mechanism of material formation.Herein,supported by theoretical simulations and various spectroscopies,we prove that P2/O3 biphasic structures essentially originate from the internal heterogeneity of cationic potential,which can be realized by constraining the temperature-driven ion diffusion during solid-state reactions.Consequently,P2/O3 biphasic Na_(0.7)Ni_(0.2)Cu_(0.1)Fe_(0.2)Mn_(0.5)O_(2)-δ with well-designed quaternary composition is successfully obtained,exhibiting much-improved rate capabilities(62 mAh g^(-1)at 2.4 A g^(-1)) and cycling stabilities(84%capacity retention after 500 cycles)than its single-phase analogues.Furthermore,synchrotron-based diffraction and X-ray absorption spectroscopy are employed to unravel the underlying sodium-storage mechanism of the P2/O3 biphasic structure.This work presents new insights toward the rational design of advanced layered cathodes for sodium-ion batteries.
文摘Coal is still a major source of energy, also a major source of SO_2, NOx and CO_2 emission though. Removal of SO_2 and NOx doubled the cost of power generation, and capture of CO_2 is equivalent to double the market price of power coal. The GCP (green coal power) is the power generated in coal-combustion with zero emission. The author indicates that it is possible to make coal-fired power plants emission free based on thermodynamic analysis and purposely designed experiments using SFG (simulated flue gases). It is concluded in the study that all SO_2 and NOx in the post-combustion flue gas are reduced to inoffensive substances at temperature lower than 750 ℃ when contacting carbon and elemental sulfur is separated in succeeded cooling of flue gas at temperatures 200-400 ℃, and the ultrafine dusts are trapped in condensed water at temperature blow 100 ℃. Based on chemical engineering expertise the author is sure that the cost for removing acid gases is much lower than any clean coal technologies known to today. Instead of capture, the remained CO_2 is converted to CO in the second time contact with carbon at 900-950 ℃. CO is the raw material of chemical synthesis and, thus, CO_2 is stored in chemical products such as methanol, fertilizer, plastics, etc. The simple and low-cost processing allows GCP utilized in practice easily.
文摘Steady-state model of a high-temperature solid oxide fuel cell (SOFC) is considered, which refers to constant chemical potentials of incoming hydrogen fuel and oxidant. Lowering of the cell voltage below its reversible value is attributed to polarizations and imperfect conversions of reactions. An imperfect power formula summarizes the effect of transport laws, irreversible polarizations and efficiency of power yield. Reversible electrochemical theory is extended to the case with dissipative chemical reactions; this case includes systems with incomplete conversions, characterized by "reduced affinities" and an idle run voltage. Efficiency drop is linked with thermodynamic and electrochemical irreversibilities expressed in terms of polarizations (activation, concentration and ohmic). Effect of incomplete conversions is modeled by assuming that substrates can be remained after the reaction and that side reactions may occur. Optimum and feasibility conditions are discussed for basic input parameters of the cell. Calculations of maximum power show that the data differ for power generated and consumed and depend on current intensity, number of mass transfer units, polarizations, electrode surface area, average chemical rate, etc.. These data provide bounds for SOFC energy generators, which are more exact and informative than reversible bounds for electrochemical transformation.
文摘Based on thermodynamics and physical chemistry theory,the theoretical energy consumption (TEC) of the typical separating processes of Al,Ca and Mg has been calculated and analyzed.This paper attempts to prove that the thermal method is more reasonable than the electrolytic methods to separate Al,Ca and Mg under the domestic circumstances of the low efficiency of coal-firing power plant at present.