Joint time–frequency analysis is an emerging method for interpreting the underlying physics in fuel cells,batteries,and supercapacitors.To increase the reliability of time–frequency analysis,a theoretical correlatio...Joint time–frequency analysis is an emerging method for interpreting the underlying physics in fuel cells,batteries,and supercapacitors.To increase the reliability of time–frequency analysis,a theoretical correlation between frequency-domain stationary analysis and time-domain transient analysis is urgently required.The present work formularizes a thorough model reduction of fractional impedance spectra for electrochemical energy devices involving not only the model reduction from fractional-order models to integer-order models and from high-to low-order RC circuits but also insight into the evolution of the characteristic time constants during the whole reduction process.The following work has been carried out:(i)the model-reduction theory is addressed for typical Warburg elements and RC circuits based on the continued fraction expansion theory and the response error minimization technique,respectively;(ii)the order effect on the model reduction of typical Warburg elements is quantitatively evaluated by time–frequency analysis;(iii)the results of time–frequency analysis are confirmed to be useful to determine the reduction order in terms of the kinetic information needed to be captured;and(iv)the results of time–frequency analysis are validated for the model reduction of fractional impedance spectra for lithium-ion batteries,supercapacitors,and solid oxide fuel cells.In turn,the numerical validation has demonstrated the powerful function of the joint time–frequency analysis.The thorough model reduction of fractional impedance spectra addressed in the present work not only clarifies the relationship between time-domain transient analysis and frequency-domain stationary analysis but also enhances the reliability of the joint time–frequency analysis for electrochemical energy devices.展开更多
The commercialization of a polymer membrane H2-O2 fuel cell and its widespread use call for the development of cost-effective oxygen reduction reaction(ORR)nonplatinum group metal(NPGM)catalysts.Nevertheless,to meet t...The commercialization of a polymer membrane H2-O2 fuel cell and its widespread use call for the development of cost-effective oxygen reduction reaction(ORR)nonplatinum group metal(NPGM)catalysts.Nevertheless,to meet the requests for the real-world fuel cell application and replacing platinum catalysts,it still needs to address some challenges for NPGM catalysts regarding the sluggish ORR kinetics in the cathode and their poor durability in acidic environment.In response to these issues,numerous efforts have been made to study NPGM catalysts both theoretically and experimentally,developed these into the atomically dispersed coordinated metal-nitrogen-carbon(M-N-C)form over the past decades.In this review,we present a comprehensive summary of recent advancements on NPGM catalysts with high activity and durability.Catalyst design strategies in terms of optimizing active-site density and enhancing catalyst stability against demetalization and carbon corrosion are highlighted.It is also emphasized the importance of understanding the mechanisms and principles behind those strategies through a combination of theoretical modeling and experimental work.Especially,further understanding the mechanisms related to the active-site structure and the formation process of the single-atom active site under pyrolysis conditions is critical for active-site engineering.Optimizing the active-site distance is the basic principle for improving catalyst activity through increasing the catalyst active-site density.Theoretical studies for the catalyst deactivation mechanism and modeling stable active-site structures provide both mechanisms and principles to improve the NPGM catalyst durability.Finally,currently remained challenges and perspectives in the future on designing high-performance atomically dispersed NPGM catalysts toward fuel cell application are discussed.展开更多
Solid oxide fuel cells(SOFCs)have attracted a great deal of interest because they have the highest efficiency without using any noble metal as catalysts among all the fuel cell technologies.However,traditional SOFCs s...Solid oxide fuel cells(SOFCs)have attracted a great deal of interest because they have the highest efficiency without using any noble metal as catalysts among all the fuel cell technologies.However,traditional SOFCs suffer from having a higher volume,current leakage,complex connections,and difficulty in gas sealing.To solve these problems,Rolls-Royce has fabricated a simple design by stacking cells in series on an insulating porous support,resulting in the tubular segmented-in-series solid oxide fuel cells(SIS-SOFCs),which achieved higher output voltage.This work systematically reviews recent advances in the structures,preparation methods,perform-ances,and stability of tubular SIS-SOFCs in experimental and numerical studies.Finally,the challenges and future development of tubular SIS-SOFCs are also discussed.The findings of this work can help guide the direction and inspire innovation of future development in this field.展开更多
Attaining a decarbonized and sustainable energy system,which is the core solution to global energy issues,is accessible through the development of hydrogen energy.Proton-exchange membrane water electrolyzers(PEMWEs)ar...Attaining a decarbonized and sustainable energy system,which is the core solution to global energy issues,is accessible through the development of hydrogen energy.Proton-exchange membrane water electrolyzers(PEMWEs)are promising devices for hydrogen production,given their high efficiency,rapid responsiveness,and compactness.Bipolar plates account for a relatively high percentage of the total cost and weight compared with other components of PEMWEs.Thus,optimization of their design may accelerate the promotion of PEMWEs.This paper reviews the advances in materials and flow-field design for bipolar plates.First,the working conditions of proton-exchange membrane fuel cells(PEMFCs)and PEMWEs are compared,including reaction direction,operating temperature,pressure,input/output,and potential.Then,the current research status of bipolar-plate substrates and surface coatings is summarized,and some typical channel-rib flow fields and porous flow fields are presented.Furthermore,the effects of materials on mass and heat transfer and the possibility of reducing corrosion by improving the flow field structure are explored.Finally,this review discusses the potential directions of the development of bipolar-plate design,including material fabrication,flow-field geometry optimization using threedimensional printing,and surface-coating composition optimization based on computational materials science.展开更多
Ensuring the consistency of electrode structure in proton-exchange-membrane fuel cells is highly desired yet challenging because of wide-existing and unguided cracks in the microporous layer(MPL). The first thing is t...Ensuring the consistency of electrode structure in proton-exchange-membrane fuel cells is highly desired yet challenging because of wide-existing and unguided cracks in the microporous layer(MPL). The first thing is to evaluate the homogeneity of MPL with cracks quantitatively. This paper proposes the homogeneity index of a full-scale MPL with an area of 50 cm~2, which is yet to be reported in the literature to our knowledge. Besides, the effects of the carbon material and surfactant on the ink and resulting MPL structure have been studied. The ink with a high network development degree produces an MPL with low crack density, but the ink with high PDI produces an MPL with low crack homogeneity. The polarity of the surfactant and the non-polarity of polytetrafluoroethylene(PTFE) are not mutually soluble,resulting in the heterogeneous PTFE distribution. The findings of this study provide guidelines for MPL fabrication.展开更多
This study used a three-dimensional numerical model of a proton exchange membrane fuel cell with five types of channels:a smooth channel(Case 1);eight rectangular baffles were arranged in the upstream(Case 2),midstrea...This study used a three-dimensional numerical model of a proton exchange membrane fuel cell with five types of channels:a smooth channel(Case 1);eight rectangular baffles were arranged in the upstream(Case 2),midstream(Case 3),downstream(Case 4),and the entire cathode flow channel(Case 5)to study the effects of baffle position on mass transport,power density,net power,etc.Moreover,the effects of back pressure and humidity on the voltage were investigated.Results showed that compared to smooth channels,the oxygen and water transport facilitation at the diffusion layer-channel interface were added 11.53%-20.60%and 7.81%-9.80%at 1.68 A·cm^(-2)by adding baffles.The closer the baffles were to upstream,the higher the total oxygen flux,but the lower the flux uniformity the worse the water removal.The oxygen flux of upstream baffles was 8.14%higher than that of downstream baffles,but oxygen flux uniformity decreased by 18.96%at 1.68 A·cm^(-2).The order of water removal and voltage improvement was Case 4>Case 5>Case 3>Case 2>Case 1.Net power of Case 4 was 9.87%higher than that of the smooth channel.To the Case 4,when the cell worked under low back pressure or high humidity,the voltage increments were higher.The potential increment for the back pressure of 0 atm was 0.9%higher than that of 2 atm(1 atm=101.325 kPa).The potential increment for the humidity of 100%was 7.89%higher than that of 50%.展开更多
Highly-efficient oxidation of 5-hydroxymethylfurtural(HMF) to 2,5-furandicarboxylic acid(FDCA) at low temperature with air as the oxidant is still challenging.Herein,inspired by the respirato ry electron transport cha...Highly-efficient oxidation of 5-hydroxymethylfurtural(HMF) to 2,5-furandicarboxylic acid(FDCA) at low temperature with air as the oxidant is still challenging.Herein,inspired by the respirato ry electron transport chain(ETC) of living cells mediated by electron carriers,we constructed artificial ETCs and transformed liquid flow fuel cells(LFFCs) to flexible reactors for efficient oxidation of HMF to produce FDCA under mild conditions.This LFFC reactor employed an electrodeposition modified nickel foam as an anode to promote HMF oxidation and(VO_(2))_(2)SO_(4) as a cathode electron carrier to facilitate the electron transfer to air.The reaction rate could be easily controlled by selecting the anode catalyst,adjusting the external loading and changing the cathodic electron carrier or oxidants.A maximal power density of 44.9 mW cm^(-2) at room temperature was achieved,while for FDCA production,short-circuit condition was preferred to achieve quick transfer of electrons.For a single batch operation with 0.1 M initial HMF,FDCA yield reached 97.1%.By fed-batch operation,FDCA concentration reached 144.5 g L^(-1) with a total yield of 96%.Ni^(2+)/Ni^(3+) redox couple was the active species mediating the electron transfer,while both experimental and DFT calculation results indicated that HMFCA pathway was the preferred reaction mechanism.展开更多
A suitable channel structure can lead to efficient gas distribution and significantly improve the power density of fuel cells.In this study,the influence of two channel design parameters is investigated,namely,the rat...A suitable channel structure can lead to efficient gas distribution and significantly improve the power density of fuel cells.In this study,the influence of two channel design parameters is investigated,namely,the ratio of the channel width to the bipolar plate ridge width(i.e.,the channel ridge ratio)and the channel depth.The impact of these parameters is evaluated with respect to the flow pattern,the gas composition distribution,the temperature field and the fuel cell output capability.The results show that a decrease in the channel ridge ratio and an increase in the channel depth can effectively make the distributions of velocity,temperature and concentration more uniform in each channel and improve the output capability of the fuel cell.An increase in the channel ridge ratio and depth obviously reduces the flow resistance and improves the flow characteristics.展开更多
Fe-N-doped carbon materials(Fe-N-C)are promising candidates for oxygen reduction reaction(ORR)relative to Pt-based catalysts in proton exchange membrane fuel cells(PEMFCs).However,the intrinsic contributions of Fe-N_(...Fe-N-doped carbon materials(Fe-N-C)are promising candidates for oxygen reduction reaction(ORR)relative to Pt-based catalysts in proton exchange membrane fuel cells(PEMFCs).However,the intrinsic contributions of Fe-N_(4)moiety with different chemical/spin states(e.g.D1,D2,D3)to ORR are unclear since various states coexist inevitably.In the present work,Fe-N-C core-shell nanocatalyst with single lowspin Fe(Ⅱ)-N_(4)species(D1)is synthesized and identified with ex-situ ultralow temperature Mossbauer spectroscopy(T=1.6 K)that could essentially differentiate various Fe-N_(4)states and invisible Fe-O species.By quantifying with CO-pulse chemisorption,site density and turnover frequency of Fe-N-C catalysts reach 2.4×10^(-9)site g^(-1)and 23 e site~(-1)s^(-1)during the ORR,respectively.Half-wave potential(0.915V_(RHE))of the Fe-N-C catalyst is more positive(approximately 54 mV)than that of Pt/C.Moreover,we observe that the performance of PEMFCs on Fe-N-C almost achieves the 2025 target of the US Department of Energy by demonstrating a current density of 1.037 A cm^(-2)combined with the peak power density of 0,685 W cm^(-2),suggesting the critical role of Fe(Ⅱ)-N_(4)site(D1).After 500 h of running,PEMFCs still deliver a power density of 1.26 W cm^(-2)at 1.0 bar H_(2)-O_(2),An unexpected rate-determining step is figured out by isotopic labelling experiment and theoretical calculation.This work not only offers valuable insights regarding the intrinsic contribution of Fe-N_(4)with a single spin state to alkaline/acidic ORR,but also provides great opportunities for developing high-performance stable PEMFCs.展开更多
Surface/interface engineering of a multimetallic nanostructure with diverse electrocatalytic properties for direct liquid fuel cells is desirable yet challenging.Herein,using visible light,a class of quaternary Pt_(1)...Surface/interface engineering of a multimetallic nanostructure with diverse electrocatalytic properties for direct liquid fuel cells is desirable yet challenging.Herein,using visible light,a class of quaternary Pt_(1)Ag_(0.1)Bi_(0.16)Te_(0.29)ultrathin nanosheets is fabricated and used as high-performance anode electrocatalysts for formic acid-/alcohol-air fuel cells.The modified electronic structure of Pt,enhanced hydroxyl adsorption,and abundant exterior defects afford Pt_(1)Ag_(0.1)Bi_(0.16)Te_(0.29)/C high intrinsic anodic electrocatalytic activity to boost the power densities of direct formic acid-/methanol-/ethanol-/ethylene glycol-/glycerol-air fuel cells,and the corresponding peak power density of Pt_(1)Ag_(0.1)Bi_(0.16)Te_(0.29)/C is respectively 129.7,142.3,105.4,124.3,and 128.0 mW cm^(-2),considerably outperforming Pt/C.Operando in situ Fourier transform infrared reflection spectroscopy reveals that formic acid oxidation on Pt_(1)Ag_(0.1)Bi_(0.16)Te_(0.29)/C occurs via a CO_(2)-free direct pathway.Density functional theory calculations show that the presence of Ag,Bi,and Te in Pt_(1)Ag_(0.1)Bi_(0.16)Te_(0.29)suppresses CO^(*)formation while optimizing dehydrogenation steps and synergistic effect and modified Pt effectively enhance H_(2)O dissociation to improve electrocatalytic performance.This synthesis strategy can be extended to 43 other types of ultrathin multimetallic nanosheets(from ternary to octonary nanosheets),and efficiently capture precious metals(i.e.,Pd,Pt,Rh,Ru,Au,and Ag)from different water sources.展开更多
Developing efficient and stable cathodes for low-temperature solid oxide fuel cells(LT-SOFCs) is of great importance for the practical commercialization.Herein,we propose a series of Sm-modified Bi_(0.7-x)Sm_xSr_(0.3)...Developing efficient and stable cathodes for low-temperature solid oxide fuel cells(LT-SOFCs) is of great importance for the practical commercialization.Herein,we propose a series of Sm-modified Bi_(0.7-x)Sm_xSr_(0.3)FeO_(3-δ) perovskites as highly-active catalysts for LT-SOFCs.Sm doping can significantly enhance the electrocata lytic activity and chemical stability of cathode.At 600℃,Bi_(0.675)Sm_(0.025)Sr_(0.3)FeO_(3-δ)(BSSF25) cathode has been found to be the optimum composition with a polarization resistance of 0.098 Ω cm^2,which is only around 22.8% of Bi_(0.7)Sr_(0.3)FeO_(3-δ)(BSF).A full cell utilizing BSSF25 displays an exceptional output density of 790 mW cm^(-2),which can operate continuously over100 h without obvious degradation.The remarkable electrochemical performance observed can be attributed to the improved O_(2) transport kinetics,superior surface oxygen adsorption capacity,as well as O_(2)p band centers in close proximity to the Fermi level.Moreover,larger average bonding energy(ABE) and the presence of highly acidic Bi,Sm,and Fe ions restrict the adsorption of CO_(2) on the cathode surface,resulting in excellent CO_(2) resistivity.This work provides valuable guidance for systematic design of efficient and durable catalysts for LT-SOFCs.展开更多
For present solid oxide fuel cells(SOFCs),rapid performance degradation is observed in the initial aging process,and the dis-cussion of the degradation mechanism necessitates quantitative analysis.Herein,focused ion b...For present solid oxide fuel cells(SOFCs),rapid performance degradation is observed in the initial aging process,and the dis-cussion of the degradation mechanism necessitates quantitative analysis.Herein,focused ion beam-scanning electron microscopy was em-ployed to characterize and reconstruct the ceramic microstructures of SOFC anodes.The lattice Boltzmann method(LBM)simulation of multiphysical and electrochemical processes in the reconstructed models was performed.Two samples collected from industrial-size cells were characterized,including a reduced reference cell and a cell with an initial aging process.Statistical parameters of the reconstructed microstructures revealed a significant decrease in the active triple-phase boundary and Ni connectivity in the aged cell compared with the reference cell.The LBM simulation revealed that activity degradation is dominant compared with microstructural degradation during the initial aging process,and the electrochemical reactions spread to the support layer in the aged cell.The microstructural and activity de-gradations are attributed to Ni migration and coarsening.展开更多
The open ratio of a current collector has a great impact on direct methanol fuel cell(DMFC)performance.Although a number of studies have investigated the influence of the open ratio of DMFC current collectors,far too ...The open ratio of a current collector has a great impact on direct methanol fuel cell(DMFC)performance.Although a number of studies have investigated the influence of the open ratio of DMFC current collectors,far too little attention has been given to how geometry(including the shape and feature size of the flow field)affects a current collector with an equal open ratio.In this paper,perforated and parallel current collectors with an equal open ratio of 50%and different feature sizes are designed,and the corresponding experimental results are shown to explain the geometry effects on the output power of the DMFC.The results indicate that the optimal feature sizes are between 2 and 2.5 mm for both perforated and parallel flow field in the current collectors with an equal open ratio of 50%.This means that for passive methanol fuel cells,to achieve the highest output power,the optimal feature size of the flow field in both anode and cathode current collectors is between 2 and 2.5 mm under the operating mode of this experiment.The effects of rib and channel position are also investigated,and the results indicate that the optimum pattern depends on the feature sizes of the flow field.展开更多
PrBa_(0.5)Sr_(0.5)Co_(1.5)Fe_(0.5)O_(5+δ)(PrBSCF) has attracted much research interest as a potential triple ionic and electronic conductor(TIEC) electrode for protonic ceramic fuel cells(PCFCs). The chemical formula...PrBa_(0.5)Sr_(0.5)Co_(1.5)Fe_(0.5)O_(5+δ)(PrBSCF) has attracted much research interest as a potential triple ionic and electronic conductor(TIEC) electrode for protonic ceramic fuel cells(PCFCs). The chemical formula for Pr BSCF is AA'B_(2)O_(5+δ), with Pr(A-site) and Ba/Sr(A'-site) alternately stacked along the c-axis. Due to these structural features, the bulk oxygen ion diffusivity is significantly enhanced through the disorder-free channels in the PrO layer;thus, the A site cations(lanthanide ions) play a pivotal role in determining the overall electrochemical properties of layered perovskites. Consequently, previous research has predominantly focused on the electrical properties and oxygen bulk/surface kinetics of Ln cation effects,whereas the hydration properties for PCFC systems remain unidentified. Here, we thoroughly examined the proton uptake behavior and thermodynamic parameters for the hydration reaction to conclusively determine the changes in the electrochemical performances depending on LnBa_(0.5)Sr_(0.5)Co_(1.5)Fe_(0.5)O_(5+δ)(LnBSCF,Ln=Pr, Nd, and Gd) cathodes. At 500 ℃, the quantitative proton concentration of PrBSCF was 2.04 mol% and progressively decreased as the Ln cation size decreased. Similarly, the Gibbs free energy indicated that less energy was required for the formation of protonic defects in the order of Pr BSCF < Nd BSCF < Gd BSCF. To elucidate the close relationship between hydration properties and electrochemical performances in LnBSCF cathodes, PCFC single cell measurements and analysis of the distribution of relaxation time were further investigated.展开更多
The long-range periodically ordered atomic structures in intermetallic nanoparticles(INPs)can significantly enhance both the electrocatalytic activity and electrochemical stability toward the oxygen reduction reaction...The long-range periodically ordered atomic structures in intermetallic nanoparticles(INPs)can significantly enhance both the electrocatalytic activity and electrochemical stability toward the oxygen reduction reaction(ORR)compared to the disordered atomic structures in ordinary solid-solution alloy NPs.Accordingly,through a facile and scalable synthetic method,a series of carbon-supported ultrafine Pt_3Co_(x)Mn_(1-x)ternary INPs are prepared in this work,which possess the"skin-like"ultrathin Pt shells,the ordered L1_(2) atomic structure,and the high-even dispersion on supports(L1_(2)-Pt_3Co_(x)Mn_(1-x)/~SPt INPs/C).Electrochemical results present that the composition-optimized L1_(2)-Pt_3Co_(0.7)Mn_(0.3)/~SPt INPs/C exhibits the highest electrocata lytic activity among the series,which are also much better than those of the pristine ultrafine Pt/C.Besides,it also has a greatly enhanced electrochemical stability.In addition,the effects of annealing temperature and time are further investigated.More importantly,such superior ORR electrocatalytic performance of L1_(2)-Pt_3Co_(0.7)Mn_(0.3)/~SPt INPs/C are also well demonstrated in practical fuel cells.Physicochemical characterization analyses further reveal the major origins of the greatly enhanced ORR electrocata lytic performance:the Pt-Co-Mn alloy-induced geometric and ligand effects as well as the extremely high L1_(2) atomic-ordering degree.This work not only successfully develops a highly active and stable ordered ternary intermetallic ORR electrocatalyst,but also elucidates the corresponding"structure-function"relationship,which can be further applied in designing other intermetallic(electro)catalysts.展开更多
Proton exchange membrane fuel cells are widely regarded as having the potential to replace internal combustion engines in vehicles.Since fuel cells cannot recover energy and have a slow dynamic response,they need to b...Proton exchange membrane fuel cells are widely regarded as having the potential to replace internal combustion engines in vehicles.Since fuel cells cannot recover energy and have a slow dynamic response,they need to be used with different power sources.Developing efficient energy management strategies to achieve excellent fuel economy is the goal of research.This paper proposes an adaptive equivalent fuel minimum consumption strategy(AECMS)to solve the problem of the poor economy of the whole vehicle caused by the wrong selection of equivalent factors(EF)in traditional ECMS.In this method,the kinematics interval is used to update the equivalent factor by considering the penalty term of energy recovery on SOC changes.Finally,the optimized equivalent factor is substituted into the optimization objective function to achieve efficient energy regulation.Simulation results under the New European Driving Cycle show that compared with the traditional ECMS based on fixed SOC benchmarks,the proposed method improves fuel economy by 1.7%while ensuring vehicle power and increases SOC by 30%.展开更多
In order to improve the performance degradation prediction accuracy of proton exchange membrane fuel cell(PEMFC),a fusion prediction method(CKDG)based on adaptive noise complete ensemble empirical mode decomposition(C...In order to improve the performance degradation prediction accuracy of proton exchange membrane fuel cell(PEMFC),a fusion prediction method(CKDG)based on adaptive noise complete ensemble empirical mode decomposition(CEEMDAN),kernel principal component analysis(KPCA)and dual attention mechanism gated recurrent unit neural network(DA-GRU)was proposed.CEEMDAN and KPCA were used to extract the input feature data sequence,reduce the influence of random factors,and capture essential feature components to reduce the model complexity.The DA-GRU network helps to learn the feature mapping relationship of data in long time series and predict the changing trend of performance degradation data more accurately.The actual aging experimental data verify the performance of the CKDG method.The results show that under the steady-state condition of 20%training data prediction,the CKDA method can reduce the root mean square error(RMSE)by 52.7%and 34.6%,respectively,compared with the traditional LSTM and GRU neural networks.Compared with the simple DA-GRU network,RMSE is reduced by 15%,and the degree of over-fitting is reduced,which has higher accuracy.It also shows excellent prediction performance under the dynamic condition data set and has good universality.展开更多
基金support from the National Science Foundation of China(22078190)the National Key R&D Plan of China(2020YFB1505802).
文摘Joint time–frequency analysis is an emerging method for interpreting the underlying physics in fuel cells,batteries,and supercapacitors.To increase the reliability of time–frequency analysis,a theoretical correlation between frequency-domain stationary analysis and time-domain transient analysis is urgently required.The present work formularizes a thorough model reduction of fractional impedance spectra for electrochemical energy devices involving not only the model reduction from fractional-order models to integer-order models and from high-to low-order RC circuits but also insight into the evolution of the characteristic time constants during the whole reduction process.The following work has been carried out:(i)the model-reduction theory is addressed for typical Warburg elements and RC circuits based on the continued fraction expansion theory and the response error minimization technique,respectively;(ii)the order effect on the model reduction of typical Warburg elements is quantitatively evaluated by time–frequency analysis;(iii)the results of time–frequency analysis are confirmed to be useful to determine the reduction order in terms of the kinetic information needed to be captured;and(iv)the results of time–frequency analysis are validated for the model reduction of fractional impedance spectra for lithium-ion batteries,supercapacitors,and solid oxide fuel cells.In turn,the numerical validation has demonstrated the powerful function of the joint time–frequency analysis.The thorough model reduction of fractional impedance spectra addressed in the present work not only clarifies the relationship between time-domain transient analysis and frequency-domain stationary analysis but also enhances the reliability of the joint time–frequency analysis for electrochemical energy devices.
基金Guangdong High Level Innovation Research Institute,Grant/Award Numbers:2021B0909050001,2021B0909050001。
文摘The commercialization of a polymer membrane H2-O2 fuel cell and its widespread use call for the development of cost-effective oxygen reduction reaction(ORR)nonplatinum group metal(NPGM)catalysts.Nevertheless,to meet the requests for the real-world fuel cell application and replacing platinum catalysts,it still needs to address some challenges for NPGM catalysts regarding the sluggish ORR kinetics in the cathode and their poor durability in acidic environment.In response to these issues,numerous efforts have been made to study NPGM catalysts both theoretically and experimentally,developed these into the atomically dispersed coordinated metal-nitrogen-carbon(M-N-C)form over the past decades.In this review,we present a comprehensive summary of recent advancements on NPGM catalysts with high activity and durability.Catalyst design strategies in terms of optimizing active-site density and enhancing catalyst stability against demetalization and carbon corrosion are highlighted.It is also emphasized the importance of understanding the mechanisms and principles behind those strategies through a combination of theoretical modeling and experimental work.Especially,further understanding the mechanisms related to the active-site structure and the formation process of the single-atom active site under pyrolysis conditions is critical for active-site engineering.Optimizing the active-site distance is the basic principle for improving catalyst activity through increasing the catalyst active-site density.Theoretical studies for the catalyst deactivation mechanism and modeling stable active-site structures provide both mechanisms and principles to improve the NPGM catalyst durability.Finally,currently remained challenges and perspectives in the future on designing high-performance atomically dispersed NPGM catalysts toward fuel cell application are discussed.
基金supported by the National Natural Science Foundation of China (Nos.21701083 and 22179054).
文摘Solid oxide fuel cells(SOFCs)have attracted a great deal of interest because they have the highest efficiency without using any noble metal as catalysts among all the fuel cell technologies.However,traditional SOFCs suffer from having a higher volume,current leakage,complex connections,and difficulty in gas sealing.To solve these problems,Rolls-Royce has fabricated a simple design by stacking cells in series on an insulating porous support,resulting in the tubular segmented-in-series solid oxide fuel cells(SIS-SOFCs),which achieved higher output voltage.This work systematically reviews recent advances in the structures,preparation methods,perform-ances,and stability of tubular SIS-SOFCs in experimental and numerical studies.Finally,the challenges and future development of tubular SIS-SOFCs are also discussed.The findings of this work can help guide the direction and inspire innovation of future development in this field.
基金the National Natural Science Foundation of China(No.52125102)the National Key Research and Development Program of China(No.2021YFB4000101)Fundamental Research Funds for t he Central Universities(No.FRF-TP-2021-02C2)。
文摘Attaining a decarbonized and sustainable energy system,which is the core solution to global energy issues,is accessible through the development of hydrogen energy.Proton-exchange membrane water electrolyzers(PEMWEs)are promising devices for hydrogen production,given their high efficiency,rapid responsiveness,and compactness.Bipolar plates account for a relatively high percentage of the total cost and weight compared with other components of PEMWEs.Thus,optimization of their design may accelerate the promotion of PEMWEs.This paper reviews the advances in materials and flow-field design for bipolar plates.First,the working conditions of proton-exchange membrane fuel cells(PEMFCs)and PEMWEs are compared,including reaction direction,operating temperature,pressure,input/output,and potential.Then,the current research status of bipolar-plate substrates and surface coatings is summarized,and some typical channel-rib flow fields and porous flow fields are presented.Furthermore,the effects of materials on mass and heat transfer and the possibility of reducing corrosion by improving the flow field structure are explored.Finally,this review discusses the potential directions of the development of bipolar-plate design,including material fabrication,flow-field geometry optimization using threedimensional printing,and surface-coating composition optimization based on computational materials science.
基金supported by China National Postdoctoral Program for Innovative Talents (BX20230121)China Postdoctoral Science Foundation (2023M741163)Shanghai Super Postdoctoral Incentive Program (2023741)。
文摘Ensuring the consistency of electrode structure in proton-exchange-membrane fuel cells is highly desired yet challenging because of wide-existing and unguided cracks in the microporous layer(MPL). The first thing is to evaluate the homogeneity of MPL with cracks quantitatively. This paper proposes the homogeneity index of a full-scale MPL with an area of 50 cm~2, which is yet to be reported in the literature to our knowledge. Besides, the effects of the carbon material and surfactant on the ink and resulting MPL structure have been studied. The ink with a high network development degree produces an MPL with low crack density, but the ink with high PDI produces an MPL with low crack homogeneity. The polarity of the surfactant and the non-polarity of polytetrafluoroethylene(PTFE) are not mutually soluble,resulting in the heterogeneous PTFE distribution. The findings of this study provide guidelines for MPL fabrication.
基金financially supported by the Science&Technology Project of Beijing Education Committee(KM202210005013)National Natural Science Foundation of China(52306180)。
文摘This study used a three-dimensional numerical model of a proton exchange membrane fuel cell with five types of channels:a smooth channel(Case 1);eight rectangular baffles were arranged in the upstream(Case 2),midstream(Case 3),downstream(Case 4),and the entire cathode flow channel(Case 5)to study the effects of baffle position on mass transport,power density,net power,etc.Moreover,the effects of back pressure and humidity on the voltage were investigated.Results showed that compared to smooth channels,the oxygen and water transport facilitation at the diffusion layer-channel interface were added 11.53%-20.60%and 7.81%-9.80%at 1.68 A·cm^(-2)by adding baffles.The closer the baffles were to upstream,the higher the total oxygen flux,but the lower the flux uniformity the worse the water removal.The oxygen flux of upstream baffles was 8.14%higher than that of downstream baffles,but oxygen flux uniformity decreased by 18.96%at 1.68 A·cm^(-2).The order of water removal and voltage improvement was Case 4>Case 5>Case 3>Case 2>Case 1.Net power of Case 4 was 9.87%higher than that of the smooth channel.To the Case 4,when the cell worked under low back pressure or high humidity,the voltage increments were higher.The potential increment for the back pressure of 0 atm was 0.9%higher than that of 2 atm(1 atm=101.325 kPa).The potential increment for the humidity of 100%was 7.89%higher than that of 50%.
基金supported by the National Key R&D Program of China(2022YFA2105900)the National Natural Science Foundation of China(22178197)。
文摘Highly-efficient oxidation of 5-hydroxymethylfurtural(HMF) to 2,5-furandicarboxylic acid(FDCA) at low temperature with air as the oxidant is still challenging.Herein,inspired by the respirato ry electron transport chain(ETC) of living cells mediated by electron carriers,we constructed artificial ETCs and transformed liquid flow fuel cells(LFFCs) to flexible reactors for efficient oxidation of HMF to produce FDCA under mild conditions.This LFFC reactor employed an electrodeposition modified nickel foam as an anode to promote HMF oxidation and(VO_(2))_(2)SO_(4) as a cathode electron carrier to facilitate the electron transfer to air.The reaction rate could be easily controlled by selecting the anode catalyst,adjusting the external loading and changing the cathodic electron carrier or oxidants.A maximal power density of 44.9 mW cm^(-2) at room temperature was achieved,while for FDCA production,short-circuit condition was preferred to achieve quick transfer of electrons.For a single batch operation with 0.1 M initial HMF,FDCA yield reached 97.1%.By fed-batch operation,FDCA concentration reached 144.5 g L^(-1) with a total yield of 96%.Ni^(2+)/Ni^(3+) redox couple was the active species mediating the electron transfer,while both experimental and DFT calculation results indicated that HMFCA pathway was the preferred reaction mechanism.
基金This work was sponsored by the National Key R&D Program of China[Grant Number 2020YFB0106603]the Key R&D Program of Shandong Province[Grant Number 2020CXGC010404]the Undergraduate School of Shandong University,China[Grant Number 2022Y155].
文摘A suitable channel structure can lead to efficient gas distribution and significantly improve the power density of fuel cells.In this study,the influence of two channel design parameters is investigated,namely,the ratio of the channel width to the bipolar plate ridge width(i.e.,the channel ridge ratio)and the channel depth.The impact of these parameters is evaluated with respect to the flow pattern,the gas composition distribution,the temperature field and the fuel cell output capability.The results show that a decrease in the channel ridge ratio and an increase in the channel depth can effectively make the distributions of velocity,temperature and concentration more uniform in each channel and improve the output capability of the fuel cell.An increase in the channel ridge ratio and depth obviously reduces the flow resistance and improves the flow characteristics.
基金financial support from the“Hundred Talents Program”of the Chinese Academy of Sciencesthe“Young Talents Training Program”of the Shanghai Branch of the Chinese Academy of Sciences+3 种基金the financial support from the Xiamen City Natural Science Foundation of China(3502Z20227085,3502Z20227256)the National Science Youth Foundation of China(22202205)the Fujian Provincial Natural Science Foundation of China(2022J01502)Open Source Foundation of State Key Laboratory of Structural Chemistry。
文摘Fe-N-doped carbon materials(Fe-N-C)are promising candidates for oxygen reduction reaction(ORR)relative to Pt-based catalysts in proton exchange membrane fuel cells(PEMFCs).However,the intrinsic contributions of Fe-N_(4)moiety with different chemical/spin states(e.g.D1,D2,D3)to ORR are unclear since various states coexist inevitably.In the present work,Fe-N-C core-shell nanocatalyst with single lowspin Fe(Ⅱ)-N_(4)species(D1)is synthesized and identified with ex-situ ultralow temperature Mossbauer spectroscopy(T=1.6 K)that could essentially differentiate various Fe-N_(4)states and invisible Fe-O species.By quantifying with CO-pulse chemisorption,site density and turnover frequency of Fe-N-C catalysts reach 2.4×10^(-9)site g^(-1)and 23 e site~(-1)s^(-1)during the ORR,respectively.Half-wave potential(0.915V_(RHE))of the Fe-N-C catalyst is more positive(approximately 54 mV)than that of Pt/C.Moreover,we observe that the performance of PEMFCs on Fe-N-C almost achieves the 2025 target of the US Department of Energy by demonstrating a current density of 1.037 A cm^(-2)combined with the peak power density of 0,685 W cm^(-2),suggesting the critical role of Fe(Ⅱ)-N_(4)site(D1).After 500 h of running,PEMFCs still deliver a power density of 1.26 W cm^(-2)at 1.0 bar H_(2)-O_(2),An unexpected rate-determining step is figured out by isotopic labelling experiment and theoretical calculation.This work not only offers valuable insights regarding the intrinsic contribution of Fe-N_(4)with a single spin state to alkaline/acidic ORR,but also provides great opportunities for developing high-performance stable PEMFCs.
基金supported by the National Natural Science Foundation of China(21571038,22035004)the Education Department of Guizhou Province(2021312)+2 种基金the Foundation of Guizhou Province(2019-5666)the National Key R&D Program of China(2017YFA0700101)the State Key Laboratory of Physical Chemistry of Solid Surfaces(Xiamen University,202009)。
文摘Surface/interface engineering of a multimetallic nanostructure with diverse electrocatalytic properties for direct liquid fuel cells is desirable yet challenging.Herein,using visible light,a class of quaternary Pt_(1)Ag_(0.1)Bi_(0.16)Te_(0.29)ultrathin nanosheets is fabricated and used as high-performance anode electrocatalysts for formic acid-/alcohol-air fuel cells.The modified electronic structure of Pt,enhanced hydroxyl adsorption,and abundant exterior defects afford Pt_(1)Ag_(0.1)Bi_(0.16)Te_(0.29)/C high intrinsic anodic electrocatalytic activity to boost the power densities of direct formic acid-/methanol-/ethanol-/ethylene glycol-/glycerol-air fuel cells,and the corresponding peak power density of Pt_(1)Ag_(0.1)Bi_(0.16)Te_(0.29)/C is respectively 129.7,142.3,105.4,124.3,and 128.0 mW cm^(-2),considerably outperforming Pt/C.Operando in situ Fourier transform infrared reflection spectroscopy reveals that formic acid oxidation on Pt_(1)Ag_(0.1)Bi_(0.16)Te_(0.29)/C occurs via a CO_(2)-free direct pathway.Density functional theory calculations show that the presence of Ag,Bi,and Te in Pt_(1)Ag_(0.1)Bi_(0.16)Te_(0.29)suppresses CO^(*)formation while optimizing dehydrogenation steps and synergistic effect and modified Pt effectively enhance H_(2)O dissociation to improve electrocatalytic performance.This synthesis strategy can be extended to 43 other types of ultrathin multimetallic nanosheets(from ternary to octonary nanosheets),and efficiently capture precious metals(i.e.,Pd,Pt,Rh,Ru,Au,and Ag)from different water sources.
基金supported by the National Natural Science Foundation of China(22279025,21773048)the Natural Science Foundation of Heilongjiang Province(LH2021A013)+1 种基金the Sichuan Science and Technology Program(2021YFSY0022)the Fundamental Research Funds for the Central Universities(2023FRFK06005,HIT.NSRIF202204)。
文摘Developing efficient and stable cathodes for low-temperature solid oxide fuel cells(LT-SOFCs) is of great importance for the practical commercialization.Herein,we propose a series of Sm-modified Bi_(0.7-x)Sm_xSr_(0.3)FeO_(3-δ) perovskites as highly-active catalysts for LT-SOFCs.Sm doping can significantly enhance the electrocata lytic activity and chemical stability of cathode.At 600℃,Bi_(0.675)Sm_(0.025)Sr_(0.3)FeO_(3-δ)(BSSF25) cathode has been found to be the optimum composition with a polarization resistance of 0.098 Ω cm^2,which is only around 22.8% of Bi_(0.7)Sr_(0.3)FeO_(3-δ)(BSF).A full cell utilizing BSSF25 displays an exceptional output density of 790 mW cm^(-2),which can operate continuously over100 h without obvious degradation.The remarkable electrochemical performance observed can be attributed to the improved O_(2) transport kinetics,superior surface oxygen adsorption capacity,as well as O_(2)p band centers in close proximity to the Fermi level.Moreover,larger average bonding energy(ABE) and the presence of highly acidic Bi,Sm,and Fe ions restrict the adsorption of CO_(2) on the cathode surface,resulting in excellent CO_(2) resistivity.This work provides valuable guidance for systematic design of efficient and durable catalysts for LT-SOFCs.
基金the National Key R&D Program of China(No.2018YFB1502201)the Guangdong Basic and Applied Basic Research Foundation,China(No.2020A1515010551).
文摘For present solid oxide fuel cells(SOFCs),rapid performance degradation is observed in the initial aging process,and the dis-cussion of the degradation mechanism necessitates quantitative analysis.Herein,focused ion beam-scanning electron microscopy was em-ployed to characterize and reconstruct the ceramic microstructures of SOFC anodes.The lattice Boltzmann method(LBM)simulation of multiphysical and electrochemical processes in the reconstructed models was performed.Two samples collected from industrial-size cells were characterized,including a reduced reference cell and a cell with an initial aging process.Statistical parameters of the reconstructed microstructures revealed a significant decrease in the active triple-phase boundary and Ni connectivity in the aged cell compared with the reference cell.The LBM simulation revealed that activity degradation is dominant compared with microstructural degradation during the initial aging process,and the electrochemical reactions spread to the support layer in the aged cell.The microstructural and activity de-gradations are attributed to Ni migration and coarsening.
基金supported by the National Natural Science Foundation of China (No.51405342)Natural Science Foundation of Tianjin (No.20JCYBJC00050)Jiangsu Key Laboratory of Precision and Micro-Manufacturing Technology.
文摘The open ratio of a current collector has a great impact on direct methanol fuel cell(DMFC)performance.Although a number of studies have investigated the influence of the open ratio of DMFC current collectors,far too little attention has been given to how geometry(including the shape and feature size of the flow field)affects a current collector with an equal open ratio.In this paper,perforated and parallel current collectors with an equal open ratio of 50%and different feature sizes are designed,and the corresponding experimental results are shown to explain the geometry effects on the output power of the DMFC.The results indicate that the optimal feature sizes are between 2 and 2.5 mm for both perforated and parallel flow field in the current collectors with an equal open ratio of 50%.This means that for passive methanol fuel cells,to achieve the highest output power,the optimal feature size of the flow field in both anode and cathode current collectors is between 2 and 2.5 mm under the operating mode of this experiment.The effects of rib and channel position are also investigated,and the results indicate that the optimum pattern depends on the feature sizes of the flow field.
基金supported by the National Research Foundation (NRF) grant funded by the Korea government (NRF2022R1C1C1007619, NRF-2021M3H4A1A01002921, NRF2021M3I3A1084292)supported by the KIST Institutional Program (Project No. 2E32592-23-069)。
文摘PrBa_(0.5)Sr_(0.5)Co_(1.5)Fe_(0.5)O_(5+δ)(PrBSCF) has attracted much research interest as a potential triple ionic and electronic conductor(TIEC) electrode for protonic ceramic fuel cells(PCFCs). The chemical formula for Pr BSCF is AA'B_(2)O_(5+δ), with Pr(A-site) and Ba/Sr(A'-site) alternately stacked along the c-axis. Due to these structural features, the bulk oxygen ion diffusivity is significantly enhanced through the disorder-free channels in the PrO layer;thus, the A site cations(lanthanide ions) play a pivotal role in determining the overall electrochemical properties of layered perovskites. Consequently, previous research has predominantly focused on the electrical properties and oxygen bulk/surface kinetics of Ln cation effects,whereas the hydration properties for PCFC systems remain unidentified. Here, we thoroughly examined the proton uptake behavior and thermodynamic parameters for the hydration reaction to conclusively determine the changes in the electrochemical performances depending on LnBa_(0.5)Sr_(0.5)Co_(1.5)Fe_(0.5)O_(5+δ)(LnBSCF,Ln=Pr, Nd, and Gd) cathodes. At 500 ℃, the quantitative proton concentration of PrBSCF was 2.04 mol% and progressively decreased as the Ln cation size decreased. Similarly, the Gibbs free energy indicated that less energy was required for the formation of protonic defects in the order of Pr BSCF < Nd BSCF < Gd BSCF. To elucidate the close relationship between hydration properties and electrochemical performances in LnBSCF cathodes, PCFC single cell measurements and analysis of the distribution of relaxation time were further investigated.
基金supported by the National Key Research and Development Program of China(2021YFB4001301)the Science and Technology Commission of Shanghai Municipality(21DZ1208600)the Oceanic Interdisciplinary Program of Shanghai Jiao Tong University(SL2021ZD105)。
文摘The long-range periodically ordered atomic structures in intermetallic nanoparticles(INPs)can significantly enhance both the electrocatalytic activity and electrochemical stability toward the oxygen reduction reaction(ORR)compared to the disordered atomic structures in ordinary solid-solution alloy NPs.Accordingly,through a facile and scalable synthetic method,a series of carbon-supported ultrafine Pt_3Co_(x)Mn_(1-x)ternary INPs are prepared in this work,which possess the"skin-like"ultrathin Pt shells,the ordered L1_(2) atomic structure,and the high-even dispersion on supports(L1_(2)-Pt_3Co_(x)Mn_(1-x)/~SPt INPs/C).Electrochemical results present that the composition-optimized L1_(2)-Pt_3Co_(0.7)Mn_(0.3)/~SPt INPs/C exhibits the highest electrocata lytic activity among the series,which are also much better than those of the pristine ultrafine Pt/C.Besides,it also has a greatly enhanced electrochemical stability.In addition,the effects of annealing temperature and time are further investigated.More importantly,such superior ORR electrocatalytic performance of L1_(2)-Pt_3Co_(0.7)Mn_(0.3)/~SPt INPs/C are also well demonstrated in practical fuel cells.Physicochemical characterization analyses further reveal the major origins of the greatly enhanced ORR electrocata lytic performance:the Pt-Co-Mn alloy-induced geometric and ligand effects as well as the extremely high L1_(2) atomic-ordering degree.This work not only successfully develops a highly active and stable ordered ternary intermetallic ORR electrocatalyst,but also elucidates the corresponding"structure-function"relationship,which can be further applied in designing other intermetallic(electro)catalysts.
基金This work was supported by National Key R&D Program of China(Grant No.2020YFB0106603)the Key Research and Development Program of Shandong Province(Grant No.2020CXGC010406)the Key Research and Development Program of Shandong Province(Grant No.2019JZZY010912).
文摘Proton exchange membrane fuel cells are widely regarded as having the potential to replace internal combustion engines in vehicles.Since fuel cells cannot recover energy and have a slow dynamic response,they need to be used with different power sources.Developing efficient energy management strategies to achieve excellent fuel economy is the goal of research.This paper proposes an adaptive equivalent fuel minimum consumption strategy(AECMS)to solve the problem of the poor economy of the whole vehicle caused by the wrong selection of equivalent factors(EF)in traditional ECMS.In this method,the kinematics interval is used to update the equivalent factor by considering the penalty term of energy recovery on SOC changes.Finally,the optimized equivalent factor is substituted into the optimization objective function to achieve efficient energy regulation.Simulation results under the New European Driving Cycle show that compared with the traditional ECMS based on fixed SOC benchmarks,the proposed method improves fuel economy by 1.7%while ensuring vehicle power and increases SOC by 30%.
基金funded by Shaanxi Province Key Industrial Chain Project(2023-ZDLGY-24)Industrialization Project of Shaanxi Provincial Education Department(21JC018)+1 种基金Shaanxi Province Key Research and Development Program(2021ZDLGY13-02)the Open Foundation of State Key Laboratory for Advanced Metals and Materials(2022-Z01).
文摘In order to improve the performance degradation prediction accuracy of proton exchange membrane fuel cell(PEMFC),a fusion prediction method(CKDG)based on adaptive noise complete ensemble empirical mode decomposition(CEEMDAN),kernel principal component analysis(KPCA)and dual attention mechanism gated recurrent unit neural network(DA-GRU)was proposed.CEEMDAN and KPCA were used to extract the input feature data sequence,reduce the influence of random factors,and capture essential feature components to reduce the model complexity.The DA-GRU network helps to learn the feature mapping relationship of data in long time series and predict the changing trend of performance degradation data more accurately.The actual aging experimental data verify the performance of the CKDG method.The results show that under the steady-state condition of 20%training data prediction,the CKDA method can reduce the root mean square error(RMSE)by 52.7%and 34.6%,respectively,compared with the traditional LSTM and GRU neural networks.Compared with the simple DA-GRU network,RMSE is reduced by 15%,and the degree of over-fitting is reduced,which has higher accuracy.It also shows excellent prediction performance under the dynamic condition data set and has good universality.